Periodic Table

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Periodic table

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ContentsArticlesOverview 1

Periodic table 1History 9Alternative periodic tables 16Element 19Isotope 27Orbital 36

Groups 45

Group 45Group I 46Group II 49Group III 52Group IV 55Group V 60Group VI 61Group VII 63Group VIII 64Group IX 65Group X 66Group XI 67Group XII 69Group XIII 71Group XIV 72Group XV 74Group XVI 76Group XVII 78Group XVIII 83

Periods 85

Period 85Pediod 1 90Extensions 92

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Blocks 95

Block 95s-block 95p-block 96d-block 97f-block 99

Other divisions 100

Actinide 100Lanthanide 104Metal 109Metalloid 116Noble gas 117Noble metal 128Nonmetal 131Platinum group 132Post-transition metal 135Transactinide element 137Transuranium element 138Transition metal 142

See also 146

Table of nuclides 146Island of stability 149

ReferencesArticle Sources and Contributors 154Image Sources, Licenses and Contributors 159

Article LicensesLicense 162

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1

Overview

Periodic tableThe periodic table of the chemical elements (also periodic table of the elements or just the periodic table) is atabular display of the chemical elements. Although precursors to this table exist, its invention is generally credited toRussian chemist Dmitri Mendeleev in 1869, who intended the table to illustrate recurring ("periodic") trends in theproperties of the elements. The layout of the table has been refined and extended over time, as new elements havebeen discovered, and new theoretical models have been developed to explain chemical behavior.[1]

The periodic table is now ubiquitous within the academic discipline of chemistry, providing a useful framework toclassify, systematize, and compare all of the many different forms of chemical behavior. The table has found manyapplications in chemistry, physics, biology, and engineering, especially chemical engineering. The current standardtable contains 118 elements to date. (elements 1–118).

Structure

Group # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Period

1 1H

2He

2 3Li

4Be

5B

6C

7N

8O

9F

10Ne

3 11Na

12Mg

13Al

14Si

15P

16S

17Cl

18Ar

4 19K

20Ca

21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

31Ga

32Ge

33As

34Se

35Br

36Kr

5 37Rb

38Sr

39Y

40Zr

41Nb

42Mo

43Tc

44Ru

45Rh

46Pd

47Ag

48Cd

49In

50Sn

51Sb

52Te

53I

54Xe

6 55Cs

56Ba

*Lanthanoids

72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

81Tl

82Pb

83Bi

84Po

85At

86Rn

7 87Fr

88Ra

**Actinoids

104Rf

105Db

106Sg

107Bh

108Hs

109Mt

110Ds

111Rg

112Cn

113Uut

114Uuq

115Uup

116Uuh

117Uus

118Uuo

* Lanthanoids 57La

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

** Actinoids 89Ac

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

This common arrangement of the periodic table separates the lanthanoids and actinoids (the f-block) from otherelements. The wide periodic table incorporates the f-block. The extended periodic table adds the 8th and 9th periods,incorporating the f-block and adding the theoretical g-block.

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Element categories in the periodic table

Metals Metalloids Nonmetals UnknownchemicalpropertiesAlkali

metalsAlkaline

earthmetals

Inner transitionelements

Transitionelements

Othermetals

Othernonmetals

Halogens Noblegases

Lanthanides Actinides

Solids Liquids Gases UnknownPrimordial From

decaySynthetic (Undiscovered)

Other alternative periodic tables exist.Some versions of the table show a dark stair-step line along the metalloids. Metals are to the left of the line andnon-metals to the right.[2]

The layout of the periodic table demonstrates recurring ("periodic") chemical properties. Elements are listed in orderof increasing atomic number (i.e., the number of protons in the atomic nucleus). Rows are arranged so that elementswith similar properties fall into the same columns (groups or families). According to quantum mechanical theories ofelectron configuration within atoms, each row (period) in the table corresponded to the filling of a quantum shell ofelectrons. There are progressively longer periods further down the table, grouping the elements into s-, p-, d- andf-blocks to reflect their electron configuration.In printed tables, each element is usually listed with its element symbol and atomic number; many versions of thetable also list the element's atomic mass and other information, such as its abbreviated electron configuration,electronegativity and most common valence numbers.As of 2010, the table contains 118 chemical elements whose discoveries have been confirmed. Ninety-four are foundnaturally on Earth, and the rest are synthetic elements that have been produced artificially in particle accelerators.Elements 43 (technetium), 61 (promethium) and all elements greater than 83 (bismuth), beginning with 84(polonium) have no stable isotopes. The atomic mass of each of these element's isotope having the longest half-life istypically reported on periodic tables with parentheses.[3] Isotopes of elements 43, 61, 93 (neptunium) and 94(plutonium), first discovered synthetically, have since been discovered in trace amounts on Earth as products ofnatural radioactive decay processes.The primary determinant of an element's chemical properties is its electron configuration, particularly the valenceshell electrons. For instance, any atoms with four valence electrons occupying p orbitals will exhibit some similarity.The type of orbital in which the atom's outermost electrons reside determines the "block" to which it belongs. Thenumber of valence shell electrons determines the family, or group, to which the element belongs.

Subshell S G F D P

Period

1 1s

2 2s 2p

3 3s 3p

4 4s 3d 4p

5 5s 4d 5p

6 6s 4f 5d 6p

7 7s 5f 6d 7p

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8 8s 5g 6f 7d 8p

The total number of electron shells an atom has determines the period to which it belongs. Each shell is divided intodifferent subshells, which as atomic number increases are filled in roughly this order (the Aufbau principle) (seetable). Hence the structure of the table. Since the outermost electrons determine chemical properties, those with thesame number of valence electrons are grouped together.Progressing through a group from lightest element to heaviest element, the outer-shell electrons (those most readilyaccessible for participation in chemical reactions) are all in the same type of orbital, with a similar shape, but withincreasingly higher energy and average distance from the nucleus. For instance, the outer-shell (or "valence")electrons of the first group, headed by hydrogen, all have one electron in an s orbital. In hydrogen, that s orbital is inthe lowest possible energy state of any atom, the first-shell orbital (and represented by hydrogen's position in the firstperiod of the table). In francium, the heaviest element of the group, the outer-shell electron is in the seventh-shellorbital, significantly further out on average from the nucleus than those electrons filling all the shells below it inenergy. As another example, both carbon and lead have four electrons in their outer shell orbitals.Note that as atomic number (i.e., charge on the atomic nucleus) increases, this leads to greater spin-orbit couplingbetween the nucleus and the electrons, reducing the validity of the quantum mechanical orbital approximation model,which considers each atomic orbital as a separate entity.The elements ununtrium, ununquadium, ununpentium, etc. are elements that have been discovered, but so far havenot received a trivial name yet. There is a system for naming them temporarily.

Classification

GroupsA group or family is a vertical column in the periodic table. Groups are considered the most important method ofclassifying the elements. In some groups, the elements have very similar properties and exhibit a clear trend inproperties down the group. These groups tend to be given trivial (unsystematic) names, e.g., the alkali metals,alkaline earth metals, halogens, pnictogens, chalcogens, and noble gases. Some other groups in the periodic tabledisplay fewer similarities and/or vertical trends (for example Group 14), and these have no trivial names and arereferred to simply by their group numbers.

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PeriodsA period is a horizontal row in the periodic table. Although groups are the most common way of classifyingelements, there are some regions of the periodic table where the horizontal trends and similarities in properties aremore significant than vertical group trends. This can be true in the d-block (or "transition metals"), and especially forthe f-block, where the lanthanides and actinides form two substantial horizontal series of elements.

Blocks

This diagram shows the periodic table blocks.

Because of the importance of theoutermost shell, the different regionsof the periodic table are sometimesreferred to as periodic table blocks,named according to the subshell inwhich the "last" electron resides. Thes-block comprises the first two groups(alkali metals and alkaline earthmetals) as well as hydrogen andhelium. The p-block comprises the lastsix groups (groups 13 through 18) andcontains, among others, all of thesemimetals. The d-block comprisesgroups 3 through 12 and contains all ofthe transition metals. The f-block,usually offset below the rest of the periodic table, comprises the rare earth metals.

OtherThe chemical elements are also grouped together in other ways. Some of these groupings are often illustrated on theperiodic table, such as transition metals, poor metals, and metalloids. Other informal groupings exist, such as theplatinum group and the noble metals.

Periodicity of chemical propertiesThe main value of the periodic table is the ability to predict the chemical properties of an element based on itslocation on the table. It should be noted that the properties vary differently when moving vertically along thecolumns of the table than when moving horizontally along the rows.

Trends of groupsModern quantum mechanical theories of atomic structure explain group trends by proposing that elements within thesame group have the same electron configurations in their valence shell, which is the most important factor inaccounting for their similar properties. Elements in the same group also show patterns in their atomic radius,ionization energy, and electronegativity. From top to bottom in a group, the atomic radii of the elements increase.Since there are more filled energy levels, valence electrons are found farther from the nucleus. From the top, eachsuccessive element has a lower ionization energy because it is easier to remove an electron since the atoms are lesstightly bound. Similarly, a group will also see a top to bottom decrease in electronegativity due to an increasingdistance between valence electrons and the nucleus.

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Trends of periods

Periodic trend for ionization energy. Each period begins at a minimum for the alkalimetals, and ends at a maximum for the noble gases.

Elements in the same period showtrends in atomic radius, ionizationenergy, electron affinity, andelectronegativity. Moving left to rightacross a period, atomic radius usuallydecreases. This occurs because eachsuccessive element has an addedproton and electron which causes theelectron to be drawn closer to thenucleus. This decrease in atomic radiusalso causes the ionization energy toincrease when moving from left toright across a period. The more tightlybound an element is, the more energy is required to remove an electron. Similarly, electronegativity will increase inthe same manner as ionization energy because of the amount of pull that is exerted on the electrons by the nucleus.Electron affinity also shows a slight trend across a period. Metals (left side of a period) generally have a lowerelectron affinity than nonmetals (right side of a period) with the exception of the noble gases.

HistoryIn 1789, Antoine Lavoisier published a list of 33 chemical elements. Although Lavoisier grouped the elements intogases, metals, non-metals, and earths, chemists spent the following century searching for a more preciseclassification scheme. In 1829, Johann Wolfgang Döbereiner observed that many of the elements could be groupedinto triads (groups of three) based on their chemical properties. Lithium, sodium, and potassium, for example, weregrouped together as being soft, reactive metals. Döbereiner also observed that, when arranged by atomic weight, thesecond member of each triad was roughly the average of the first and the third.[4] This became known as the Law oftriads. German chemist Leopold Gmelin worked with this system, and by 1843 he had identified ten triads, threegroups of four, and one group of five. Jean Baptiste Dumas published work in 1857 describing relationships betweenvarious groups of metals. Although various chemists were able to identify relationships between small groups ofelements, they had yet to build one scheme that encompassed them all.[4]

German chemist August Kekulé had observed in 1858 that carbon has a tendency to bond with other elements in aratio of one to four. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventuallybecame known as valency. In 1864, fellow German chemist Julius Lothar Meyer published a table of the 49 knownelements arranged by valency. The table revealed that elements with similar properties often shared the samevalency.[5]

English chemist John Newlands published a series of papers in 1864 and 1865 that described his attempt atclassifying the elements: When listed in order of increasing atomic weight, similar physical and chemical propertiesrecurred at intervals of eight, which he likened to the octaves of music.[6] [7] This law of octaves, however, wasridiculed by his contemporaries.[8]

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Portrait of Dmitri Mendeleev

Russian chemistry professor Dmitri Ivanovich Mendeleev andJulius Lothar Meyer independently published their periodic tablesin 1869 and 1870, respectively. They both constructed their tablesin a similar manner: by listing the elements in a row or column inorder of atomic weight and starting a new row or column when thecharacteristics of the elements began to repeat.[9] The success ofMendeleev's table came from two decisions he made: The first wasto leave gaps in the table when it seemed that the correspondingelement had not yet been discovered.[10] Mendeleev was not thefirst chemist to do so, but he went a step further by using thetrends in his periodic table to predict the properties of thosemissing elements, such as gallium and germanium.[11] The seconddecision was to occasionally ignore the order suggested by theatomic weights and switch adjacent elements, such as cobalt andnickel, to better classify them into chemical families. With thedevelopment of theories of atomic structure, it became apparentthat Mendeleev had inadvertently listed the elements in order ofincreasing atomic number.[12]

With the development of modern quantum mechanical theories of electron configurations within atoms, it becameapparent that each row (or period) in the table corresponded to the filling of a quantum shell of electrons. InMendeleev's original table, each period was the same length. However, because larger atoms have more electronsub-shells, modern tables have progressively longer periods further down the table.[13]

In the years that followed after Mendeleev published his periodic table, the gaps he left were filled as chemistsdiscovered more chemical elements. The last naturally occurring element to be discovered was francium (referred toby Mendeleev as eka-caesium) in 1939.[14] The periodic table has also grown with the addition of synthetic andtransuranic elements. The first transuranic element to be discovered was neptunium, which was formed bybombarding uranium with neutrons in a cyclotron in 1939.[15]

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References• Atkins, P. W. (1995). The Periodic Kingdom. HarperCollins Publishers, Inc.. ISBN 0-465-07265-8.• Ball, Philip (2002). The Ingredients: A Guided Tour of the Elements. Oxford University Press.

ISBN 0-19-284100-9.• Brown, Theodore L.; LeMay, H. Eugene; Bursten, Bruce E. (2005). Chemistry: The Central Science (10th ed.).

Prentice Hall. ISBN 0-13-109686-9.• Pullman, Bernard (1998). The Atom in the History of Human Thought. Translated by Axel Reisinger. Oxford

University Press. ISBN 0-19-515040-6.

Further reading• Bouma, J. (1989). "An Application-Oriented Periodic Table of the Elements". J. Chem. Ed. 66: 741.

doi:10.1021/ed066p741.• Eric Scerri (2007). The periodic table: its story and its significance. Oxford: Oxford University Press.

ISBN 0-19-530573-6.• Mazurs, E.G (1974). Graphical Representations of the Periodic System During One Hundred Years. Alabama:

University of Alabama Press.

External links• Interactive periodic table [16]

• WebElements [17]

• IUPAC periodic table [18]

• A video for each one of the elements. [19] Made by Brady Haran, featuring Martyn Poliakoff and others, at theUniversity of Nottingham.

pni:لبیٹ کڈایریپ

References[1] IUPAC article on periodic table (http:/ / www. iupac. org/ didac/ Didac Eng/ Didac01/ Content/ S01. htm)[2] Science Standards of Learning Curriculum Framework (http:/ / www. doe. virginia. gov/ VDOE/ Instruction/ Science/ ScienceCF-PS. doc)[3] Dynamic periodic table (http:/ / www. ptable. com/ )[4] Ball, p. 100[5] Ball, p. 101[6] Newlands, John A. R. (1864-08-20). "On Relations Among the Equivalents" (http:/ / web. lemoyne. edu/ ~giunta/ EA/ NEWLANDSann.

HTML#newlands3). Chemical News 10: 94–95. .[7] Newlands, John A. R. (1865-08-18). "On the Law of Octaves" (http:/ / web. lemoyne. edu/ ~giunta/ EA/ NEWLANDSann.

HTML#newlands4). Chemical News 12: 83. .[8] Bryson, Bill (2004). A Short History of Nearly Everything. London: Black Swan. pp. 141–142. ISBN 9780552151740.[9] Ball, pp. 100–102[10] Pullman, p. 227[11] Ball, p. 105[12] Atkins, p. 87[13] Ball, p. 111[14] Adloff, Jean-Pierre; Kaufman, George B. (2005-09-25). Francium (Atomic Number 87), the Last Discovered Natural Element (http:/ /

chemeducator. org/ sbibs/ s0010005/ spapers/ 1050387gk. htm). The Chemical Educator 10 (5). Retrieved on 2007-03-26.[15] Ball, p. 123[16] http:/ / www. ptable. com/[17] http:/ / www. webelements. com/[18] http:/ / www. iupac. org/ reports/ periodic_table/ index. html[19] http:/ / www. periodicvideos. com

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HistoryThe history of the periodic table reflects over a century of growth in the understanding of chemical properties, andculminates with the publication of the first actual periodic table by Dmitri Mendeleev in 1869.[1] While Mendeleevbuilt upon earlier discoveries by such scientists as Antoine-Laurent de Lavoisier, the Russian scientist is generallygiven sole credit for development of the actual periodic table itself.The table itself is a visual representation of the periodic law which states that certain properties of elements repeatperiodically when arranged by atomic number. The table arranges elements into vertical columns (Groups) andhorizontal rows (Periods) to display these commonalities.

A modern periodic table with (colored) discovery periods.

Elemental ideas fromancient times

People have known about somechemical elements such as gold, silverand copper from antiquity, as these canall be discovered in nature in nativeform and are relatively simple to minewith primitive tools.[2] However, thenotion that there were a limitednumber of elements from whicheverything was composed originatedwith the Greek philosopher Aristotle.About 330 B.C Aristotle proposed thateverything is made up of a mixture ofone or more of four "roots" (originallyput forth by the Sicilian philosopherEmpedocles), but later renamed elements by Plato. The four elements were earth, water, air and fire. While theconcept of an element was thus introduced, Aristotle's and Plato's ideas did nothing to advance the understanding ofthe nature of matter.

Age of EnlightenmentHennig Brand was the first person recorded to have discovered a new element. Brand was a bankrupt Germanmerchant who was trying to discover the Philosopher's Stone — a mythical object that was supposed to turninexpensive base metals into gold. He experimented with distilling human urine until in 1649[3] he finally obtained aglowing white substance which he named phosphorus. He kept his discovery secret, until 1680 when Robert Boylerediscovered it and it became public. This and related discoveries raised the question of what it means for asubstance to be an "element".In 1661 Boyle defined an element as a substance that cannot be broken down into a simpler substance by a chemicalreaction. This simple definition actually served for nearly 300 years (until the development of the notion ofsubatomic particles), and even today is taught in introductory chemistry classes.

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Antoine-Laurent de Lavoisier

Antoine Laurent de Lavoisier

Lavoisier's Traité Élémentaire de Chimie (Elementary Treatise ofChemistry, 1789, translated into English by Robert Kerr) is consideredto be the first modern chemical textbook. It contained a list ofelements, or substances that could not be broken down further, whichincluded oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, andsulfur. It also forms the basis for the modern list of elements. His list,however, also included light and caloric, which he believed to bematerial substances. While many leading chemists of the time refusedto believe Lavoisier's new revelations, the Elementary Treatise waswritten well enough to convince the younger generation. However, asLavoisier's descriptions only classified elements as metals ornon-metals, it fell short of a complete analysis.

Johann Wolfgang Döbereiner

In 1817, Johann Wolfgang Döbereiner began to formulate one of the earliest attempts to classify the elements. Hefound that some elements formed groups of three with related properties. He termed these groups "triads". Sometriads classified by Döbereiner are:

1. chlorine, bromine, and iodine2. calcium, strontium, and barium3. sulfur, selenium, and tellurium4. lithium, sodium, and potassiumIn all of the triads, the atomic weight of the second element was almost exactly the average of the atomic weights ofthe first and third element.[4]

Classifying ElementsBy 1869[3] , a total of 63[3] elements had been discovered. As the number of known elements grew, scientists beganto recognize patterns in the way chemicals reacted and began to devise ways to classify the elements.

Alexandre-Emile Béguyer de ChancourtoisAlexandre-Emile Béguyer de Chancourtois, a French geologist, was the first person to notice the periodicity of theelements — similar elements seem to occur at regular intervals when they are ordered by their atomic weights. Hedevised an early form of periodic table, which he called the telluric helix. With the elements arranged in a spiral ona cylinder by order of increasing atomic weight, de Chancourtois saw that elements with similar properties lined upvertically. His chart included some ions and compounds in addition to elements. His paper was published in 1862,but used geological rather than chemical terms and did not include a diagram; as a result, it received little attentionuntil the work of Dmitri Mendeleev.[5]

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John NewlandsJohn Newlands was an English chemist who in 1865 classified[6] the 56 elements that had been discovered at thetime into 11 groups which were based on similar physical properties.

J. A. R. Newlands' law of octaves

Newlands noted that many pairs ofsimilar elements existed which differedby some multiple of eight in atomicweight. However, his law of octaves,likening this periodicity of eights to themusical scale, was ridiculed by hiscontemporaries. It was not until thefollowing century, with Gilbert N.Lewis' valence bond theory (1916) andIrving Langmuir's octet theory of chemical bonding[7] [8] (1919) that the importance of the periodicity of eight wouldbe accepted.

Dmitri Mendeleev

Mendeleev's 1869 periodic table

Dmitri Ivanovich Mendeleev

Dmitri Mendeleev, a Siberian-bornRussian chemist, was the first scientistto make a periodic table much like theone we use today. Mendeleev arrangedthe elements in a table ordered byatomic weight, corresponding torelative molar mass as defined today. Itis sometimes said that he played"chemical solitaire" on long train ridesusing cards with various facts ofknown elements.[9] On March 6, 1869,a formal presentation was made to theRussian Chemical Society, entitled TheDependence Between the Properties ofthe Atomic Weights of the Elements.His table was published in an obscureRussian journal but quicklyrepublished in a German journal,Zeitschrift für Chemie (Eng.,"Chemistry Magazine"), in 1869. Itstated:

1. The elements, if arranged accordingto their atomic weights, exhibit anapparent periodicity of properties.

2. Elements which are similar as regards to their chemical properties have atomic weights which are either of nearlythe same value (e.g., Pt, Ir, Os) or which increase regularly (e.g., K, Rb, Cs).

3. The arrangement of the elements, or of groups of elements in the order of their atomic weights, corresponds totheir so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent amongother series in that of Li, Be, Ba, C, N, O, and Sn.

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History 12

4. The elements which are the most widely diffused have small atomic weights.5. The magnitude of the atomic weight determines the character of the element, just as the magnitude of the

molecule determines the character of a compound body.6. We must expect the discovery of many yet unknown elements–for example, elements analogous to aluminium

and silicon–whose atomic weight would be between 65 and 75.7. The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous

elements. Thus the atomic weight of tellurium must lie between 123 and 126, and cannot be 128. (This was basedon the position of tellurium between antimony and iodine whose atomic weight is 127. However Moseley laterexplained the position of these elements without revising the atomic weight values — see below.)

8. Certain characteristic properties of elements can be foretold from their atomic weights.

This version of Mendeleev's periodic table from 1891. It is lacking the noble gases

Scientific benefits of Mendeleev's table

• Mendeleev predicted the discovery ofother elements and left space for thesenew elements, namely eka-silicon(germanium), eka-aluminium (gallium),and eka-boron (scandium). Thus, therewas no disturbance in the periodic table.

• He pointed out that some of the thencurrent atomic weights were incorrect.

• He provided for variance from atomicweight order.

Shortcomings of Mendeleev's table

• His table did not include any of the noblegases, which were discovered later.These were added by Sir WilliamRamsay as Group 0, without anydisturbance to the basic concept of theperiodic table.

• There was no place for the isotopes of thevarious elements, which were discoveredlater.

Lothar Meyer

Unknown to Mendeleev, Lothar Meyer was also working on a periodic table. Although his work was published in1864, and was done independently of Mendeleev, few historians regard him as an equal co-creator of the periodictable. For one thing, Meyer's table only included 28 elements. Furthermore, Meyer classified elements not by atomicweight, but by valence alone. Finally, Meyer never came to the idea of predicting new elements and correctingatomic weights. Only a few months after Mendeleev published his periodic table of all known elements (andpredicted several new elements to complete the table, plus some corrected atomic weights), Meyer published avirtually identical table. While a few people consider Meyer and Mendeleev the co-creators of the periodic table,most agree that, by itself, Mendeleev's accurate prediction of the qualities of the undiscovered elements lands himthe larger share of credit. In any case, at the time Mendeleev's predictions greatly impressed his contemporaries andwere eventually found to be correct. An English chemist, William Odling, also drew up a table that is remarkablysimilar to that of Mendeleev, in 1864.

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Refinements to the periodic table

Henry MoseleyIn 1914 Henry Moseley found a relationship between an element's X-ray wavelength and its atomic number (Z), andtherefore resequenced the table by nuclear charge rather than atomic weight. Before this discovery, atomic numberswere just sequential numbers based on an element's atomic weight. Moseley's discovery showed that atomic numbershad an experimentally measurable basis.Thus Moseley placed argon (Z=18) before potassium (Z=19) based on their X-ray wavelengths, despite the fact thatargon has a greater atomic weight (39.9) than potassium (39.1). The new order agrees with the chemical properties ofthese elements, since argon is a noble gas and potassium an alkali metal. Similarly, Moseley placed cobalt beforenickel, and was able to explain that tellurium occurs before iodine without revising the experimental atomic weightof tellurium (127.6) as proposed by Mendeleev.Moseley's research also showed that there were gaps in his table at atomic numbers 43 and 61 which are now knownto be Technetium and Promethium, respectively, both radioactive and not naturally occurring. Following in thefootsteps of Dmitri Mendeleev, Henry Moseley also predicted new elements.

Glenn T. SeaborgDuring his Manhattan Project research in 1943 Glenn T. Seaborg experienced unexpected difficulty isolatingAmericium (95) and Curium (96). He began wondering if these elements more properly belonged to a differentseries which would explain why the expected chemical properties of the new elements were different. In 1945, hewent against the advice of colleagues and proposed a significant change to Mendeleev's table: the actinide series.Seaborg's actinide concept of heavy element electronic structure, predicting that the actinides form a transition seriesanalogous to the rare earth series of lanthanide elements, is now well accepted in the scientific community andincluded in all standard configurations of the periodic table. The actinide series are the second row of the f-block (5fseries) and comprise the elements from Actinium to Lawrencium. Seaborg's subsequent elaborations of the actinideconcept theorized a series of superheavy elements in a transactinide series comprising elements 104 through 121 anda superactinide series inclusive of elements 122 through 153.

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Main discovery periodsThe history of the periodic table is also a history of the discovery of the chemical elements. IUPAC[10] suggest five"main discovery periods":

• Before 1800 (36 elements): discoveries during and before the Enlightenment.• 1800-1849 (+22 elements): impulse from scientific (empirical processes systematization and modern atomic

theory) and industrial revolutions.• 1850-1899 (+23 elements): the age of classifying elements received an impulse from the spectrum analysis.

Boisbaudran, Bunsen, Crookes, Kirchhoff, and others "hunting emission line signatures".• 1900-1949 (+13 elements): impulse from the old quantum theory, the consolitated periodic table, and quantum

mechanics.• 1950-1999 (+15 elements): "atomic bomb" and Particle physics issues, for atomic numbers 97 and above.

The periodic table as a cultural iconThroughout the 20th century, the periodic table grew in ubiquity. Its presence on a classroom wall tells themovie-viewing audience that they are viewing a science classroom. It is often provided to students takingstandardized tests as a necessary tool to complete chemical problems.In 1998, a 35-by-65 foot periodic table was constructed at the Science Museum of Virginia and is a Guinness WorldRecord. [11]

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History 15

See also• Prout's hypothesis• History of chemistry• Discoveries of the chemical elements• Periodic table• Alternative periodic tables

External links• History of the Development of the Periodic Table of Elements [12]

• Development of the periodic table [13]

• Classification of the elements [14]

• The path to the periodic table [15]

• Web page listing several scholarly and semi-popular articles on various aspects of the periodic system andunderlying theoretical concepts. Some are downloadable! [16]

• Periodic Table Database [17]

References[1] IUPAC article on periodic table (http:/ / www. iupac. org/ didac/ Didac Eng/ Didac01/ Content/ S01. htm)[2] Scerri, E. R. (2006). The Periodic Table: Its Story and Its Significance; New York City, New York; Oxford University Press.[3] "A Brief History of the Development of Periodic Table" (http:/ / www. wou. edu/ las/ physci/ ch412/ perhist. htm). .[4] Leicester, Henry M. (1971). The Historical Background of Chemistry; New York City, New York; Dover Publications.[5] Annales des Mines history page (http:/ / www. annales. org/ archives/ x/ chancourtois. html).[6] in a letter published in the Chemical News in February 1863, according to the Notable Names Data Base (http:/ / www. nndb. com/ people/

480/ 000103171/ )[7] Irving Langmuir, “The Structure of Atoms and the Octet Theory of Valence”, Proceedings of the National Academy of Science, Vol. V, 252,

Letters (1919) - online at (http:/ / dbhs. wvusd. k12. ca. us/ webdocs/ Chem-History/ Langmuir-1919. html)[8] Irving Langmuir, “The Arrangement of Electrons in Atoms and Molecules”, Journal of the American Chemical Society, Vol. 41, No, 6, pg.

868 (June 1919) - beginning and ending of the paper are transcribed online at (http:/ / dbhs. wvusd. k12. ca. us/ webdocs/ Chem-History/Langmuir-1919b. html); the middle is missing

[9] Physical Science, Holt Rinehart & Winston (January 2004), page 302 ISBN 0-03-073168-2[10] http:/ / old. iupac. org/ reports/ periodic_table/ index. html[11] "Richmond in the Record Books" (http:/ / www. richmond. com/ museums-galleries/ 6300). August 18, 2004. .[12] http:/ / www. bpc. edu/ mathscience/ chemistry/ history_of_the_periodic_table. html[13] http:/ / www. chemsoc. org/ viselements/ pages/ history. html[14] http:/ / members. optushome. com. au/ scottsofta/ Pintro. htm[15] http:/ / www. chemheritage. org/ EducationalServices/ chemach/ ppt/ ppt. html[16] http:/ / www. chem. ucla. edu/ dept/ Faculty/ scerri/ index. html[17] http:/ / www. meta-synthesis. com/ webbook/ 35_pt/ pt_database. php

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Alternative periodic tables 16

Alternative periodic tables

Theodor Benfey's periodic table

Alternative periodic tables aretabulations of chemical elementsdiffering significantly in theirorganization from the traditionaldepiction of the Periodic System.[1] [2]

Several have been devised, oftenpurely for didactic reasons, as not allcorrelations between the chemicalelements are effectively captured bythe standard periodic table. A 1974review of the tables then known isconsidered a definitive work on thetopic.[3]

Aims

Alternative periodic tables aredeveloped often to highlight oremphasize different chemical or physical properties of the elements which are not as apparent in traditional periodictables. Some tables aim to emphasize both the nucleon and electronic structure of atoms. This can be done changingthe spatial relationship or representation each element has with respect to another element in the table. Other tablesaim to emphasize the chemical element isolations by humans over time.

Major alternativesJanet's Left Step Periodic Table [4] (1928) is considered to be the most significant alternative to the traditionaldepiction of the periodic system. It organizes elements according to orbital filling and is widely used by physicists.Its modern version, known as ADOMAH Periodic Table [5], (2006) is helpful for writing electron configurations.[6]

f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14 d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 p1 p2 p3 p4 p5 p6 s1 s2

H HeLi Be

B C N O F Ne Na MgAl Si P S Cl Ar K Ca

Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb SrY Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr RaAc Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Uuq Uup Uuh Uus Uuo Uue Ubn

The Janet Periodic Table (with current element symbols).[7]

In Theodor Benfey's periodic table (1960), the elements form a two-dimensional spiral, starting from hydrogen, andfolding their way around two islands, the transition metals, and lanthanides and actinides. A superactinide island isalready slotted in. The Chemical Galaxy (2004) is organized in a similar way.

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Alternative periodic tables 17

In the extended periodic table, suggested by Glenn T. Seaborg in 1969, yet unknown elements are included up toatomic number 218. Helium is placed in the group 2 elements.

Mendeleev's 1869 periodic table

The oldest periodic table is the shortform table of Dmitri Mendeleev, whichshows secondary chemical kinships.For example, the alkali metals and thecoinage metals (copper, silver, gold)are in the same column because bothgroups tend to have a valence of one.This format is still used by many, asshown by this contemporary Russianshort form table [8] which includes allelements and element names to date.

Timmothy Stowe's physicist's periodictable is three-dimensional with the three axes representing the principal quantum number, orbital quantum number,and orbital magnetic quantum number. Helium is again a group 2 element.

Paul Giguere's 3-D periodic table consists of 4 billboards with the elements written on the front and the back. Thefirst billboard has the group 1 elements on the front and the group 2 elements at the back, with hydrogen and heliumomitted altogether. At a 90° angle the second billboard contains the groups 13 to 18 front and back. Two morebillboard each making 90° angles contain the other elements.In the research field of superatoms, clusters of atoms have properties of single atoms of another element. It issuggested to extend the periodic table with a second layer to be occupied with these cluster compounds. The latestaddition to this multi-story table is the aluminum cluster ion Al−7, which behaves like a multivalent germaniumatom.[9]

Ronald L. Rich has proposed a periodic table where elements appear more than once when appropriate.[10] He notesthat hydrogen shares properties with group 1 elements based on valency, with group 17 elements because hydrogenis a non-metal but also with the carbon group based on similarities in chemical bonding to transition metals and asimilar electronegativity. In this rendition of the periodic table carbon and silicon also appear in the same group astitanium and zirconium. An interesting new chemists' table ("Newlands Revisited") that solves many of the problemsof position of hydrogen, helium and the lanthanides, etc., was published by EG Marks and JA Marks in 2010.[11]

External links• Janet's Left Step Periodic Table [12]

• Correction to Physicist periodic table offered by Jeries Rihani [13] as Meitnerium occupies the position thatHassium should have.

• A Wired Article on Alternate Periodic Tables [14]

• A Selection of Periodic Tables [15]

• http:/ / periodicspiral. com/ arranges the periodic table in a (hexagonal) spiral.• Rotaperiod.com [16] A new periodic table.• Note [17] on the T-shirt topology of the Z-spiral.• New Periodic Table of the Elements [18] this is in a square-triangular periodic arrangement.• Periodic Table based on electron configurations [5]

• Database of Periodic Tables [17]

• Periodic Fractal of the Elements [19]

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Alternative periodic tables 18

• Bob Doyle Periodic Table of the Elements [20] A regrouping by properties that suggests a maximum of 120elements.

• Earth Scientist's Periodic Table [21]

References[1] E.R. Scerri. The Periodic Table, Its Story and Its Significance. Oxford University Press, New York, 2007.[2] Henry Bent. New Ideas in Chemistry from Fresh Energy for the Periodic Law. AuthorHouse, 2006. ISBN 9781425948627[3] Mazurs, E. G. Graphical Representations of the Periodic System During One Hundred Years. Alabama; University of Alabama Press, 1974.

ISBN 0-8173-3200-6.[4] http:/ / www. meta-synthesis. com/ webbook/ 35_pt/ pt_database. php?PT_id=152[5] http:/ / www. perfectperiodictable. com/ userguide[6] Philip J. Stewart: Charles Janet: unrecognized genius of the periodic system. Foundations of Chemistry. January, 2009. ISSN 1386-4238

(Print) ISSN 1572-8463 (Online), Vol.12, No.1 April, 2010;[7] WebElements (http:/ / www. webelements. com/ nexus/ Janet_Periodic_Table) : The Janet Periodic Table.[8] http:/ / flerovlab. jinr. ru/ flnr/ dimg/ Periodic_Table. jpg[9] Beyond The Periodic Table Metal clusters mimic chemical properties of atoms Ivan Amato Chemical & Engineering News November 21,

2006 Link (http:/ / pubs. acs. org/ cen/ news/ 84/ i48/ 8448notw8. html)[10] Rich, Ronald L. J. Chem. Educ. 2005 82 1761[11] Foundations of Chemistry 2010, 12: 85-93 (http:/ / www. springerlink. com/ content/ q7j4670426845322/ fulltext. pdf) Newlands revisited:

a display of the periodicity of the chemical elements for chemists.[12] http:/ / www. meta-synthesis. com/ webbook/ 35_pt/ pt. html#j[13] http:/ / jeries. rihani. com/ references. html[14] http:/ / www. wired. com/ wired/ archive/ 13. 10/ start. html?pg=11[15] http:/ / www. meta-synthesis. com/ webbook/ 35_pt/ pt. html[16] http:/ / www. rotaperiod. com[17] http:/ / arxiv. org/ abs/ physics/ 0603026[18] http:/ / www. egregoralfa. republika. pl/ english/ newtable. html[19] http:/ / www. superliminal. com/ pfractal. htm[20] http:/ / www. wizworld. com/ dox/ doyle_periodic_table. gif[21] http:/ / www. gly. uga. edu/ railsback/ PT. html

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ElementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number,which is the number of protons in its nucleus.[1] Common examples of elements are iron, copper, silver, gold,hydrogen, carbon, nitrogen, and oxygen. In total, 118 elements have been observed as of March 2010, of which 92occur naturally on Earth. Of these, oxygen is the most abundant element in the earth's crust. 80 elements have stableisotopes, namely all elements with atomic numbers 1 to 82, except elements 43 and 61 (technetium andpromethium). Elements with atomic numbers 83 or higher (bismuth and above) are inherently unstable, and undergoradioactive decay. The elements from atomic number 83 to 92 have no stable nuclei, but are nevertheless found innature, either surviving as remnants of the primordial stellar nucleosynthesis that produced the elements in the solarsystem, or else produced as short-lived daughter-isotopes through the natural decay of uranium and thorium.[2]

All chemical matter consists of these elements. New elements of higher atomic number are discovered from time totime, as products of artificial nuclear reactions. When two distinct elements are chemically combined, the result istermed a compound.

The periodic table of the chemical elements

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History

Mendeleev's 1869 periodic table

Ancient philosophy posited a set of classicalelements to explain patterns in nature.Elements originally referred to earth, water,air and fire rather than the chemicalelements of modern science.

The term 'elements' (stoicheia) was firstused by the Greek philosopher Plato in about360 BCE, in his dialogue Timaeus, whichincludes a discussion of the composition ofinorganic and organic bodies and is aspeculative treatise on chemistry. Platobelieved the elements introduced a centuryearlier by Empedocles were composed ofsmall polyhedral forms: tetrahedron (fire),octahedron (air), icosahedron (water), andcube (earth).[3] [4]

Aristotle, c. 350 BCE, also used the termstoicheia and added a fifth element calledaether, which formed the heavens. Aristotledefined an element as:

Element – one of those bodies intowhich other bodies can decompose,and that itself is not capable of beingdivided into other.[5]

In 1661, Robert Boyle showed that there were more than just four classical elements as the ancients had assumed.[6]

The first modern list of chemical elements was given in Antoine Lavoisier's 1789 Elements of Chemistry, whichcontained thirty-three elements, including light and caloric.[7] By 1818, Jöns Jakob Berzelius had determined atomicweights for forty-five of the forty-nine accepted elements. Dmitri Mendeleev had sixty-six elements in his periodictable of 1869.

From Boyle until the early 20th century, an element was defined as a pure substance that cannot be decomposed intoany simpler substance.[6] Put another way, a chemical element cannot be transformed into other chemical elementsby chemical processes. In 1913, Henry Moseley discovered that the physical basis of the atomic number of the atomwas its nuclear charge, which eventually led to the current definition. The current definition also avoids someambiguities due to isotopes and allotropes.By 1919, there were seventy-two known elements.[8] In 1955, element 101 was discovered and named mendeleviumin honor of Mendeleev, the first to arrange the elements in a periodic manner. In October 2006, the synthesis ofelement 118 was reported; the synthesis of element 117 was reported in April 2010.[9]

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DescriptionThe lightest elements are hydrogen and helium, both theoretically created by Big Bang nucleosynthesis during thefirst 20 minutes of the universe[10] in a ratio of around 3:1 by mass (approximately 12:1 by number of atoms).Almost all other elements found in nature, including some further hydrogen and helium created since then, weremade by various natural or (at times) artificial methods of nucleosynthesis, including occasionally breakdownactivities such as nuclear fission, alpha decay, cluster decay, and cosmic ray spallation.As of 2010, there are 118 known elements (in this context, "known" means observed well enough, even from just afew decay products, to have been differentiated from any other element).[11] [12] Of these 118 elements, 94 occurnaturally on Earth. Six of these occur in extreme trace quantities: technetium, atomic number 43; promethium,number 61; astatine, number 85; francium, number 87; neptunium, number 93; and plutonium, number 94. These 94elements, and also possibly element 98 californium, have been detected in the universe at large, in the spectra ofstars and also supernovae, where short-lived radioactive elements are newly being made.The remaining 24 elements, not found on Earth or in astronomical spectra, have been derived artificially. All of theelements that are derived solely through artificial means are radioactive with very short half-lives; if any atoms ofthese elements were present at the formation of Earth, they are extremely likely to have already decayed, and ifpresent in novae, have been in quantities too small to have been noted. Technetium was the first purportedlynon-naturally occurring element to be synthesized, in 1937, although trace amounts of technetium have since beenfound in nature, and the element may have been discovered naturally in 1925. This pattern of artificial productionand later natural discovery has been repeated with several other radioactive naturally occurring trace elements.Lists of the elements are available by name, by symbol, by atomic number, by density, by melting point, and byboiling point as well as Ionization energies of the elements. The most convenient presentation of the elements is inthe periodic table, which groups elements with similar chemical properties together.

Atomic numberThe atomic number of an element, Z, is equal to the number of protons that defines the element. For example, allcarbon atoms contain 6 protons in their nucleus; so the atomic number "Z" of carbon is 6. Carbon atoms may havedifferent numbers of neutrons; atoms of the same element having different numbers of neutrons are known asisotopes of the element.The number of protons in the atomic nucleus also determines its electric charge, which in turn determines theelectrons of the atom in its non-ionized state. This in turn (by means of the Pauli exclusion principle) determines theatom's various chemical properties. So all carbon atoms, for example, ultimately have identical chemical propertiesbecause they all have the same number of protons in their nucleus, and therefore have the same atomic number. It isfor this reason that atomic number rather than mass number (or atomic weight) is considered the identifyingcharacteristic of an element.

Atomic massThe mass number of an element, A, is the number of nucleons (protons and neutrons) in the atomic nucleus.Different isotopes of a given element are distinguished by their mass numbers, which are conventionally written as asuper-index on the left hand side of the atomic symbol (e.g., 238U).The relative atomic mass of an element is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance, relative to the atomic mass unit (u). This number may be a fraction that is not close to a whole number, due to the averaging process. On the other hand, the atomic mass of a pure isotope is quite close to its mass number. Whereas the mass number is a natural (or whole) number, the atomic mass of a single isotope is a real number that is close to a natural number. In general, it differs slightly from the mass number as the mass of the protons and neutrons is not exactly 1 u, the electrons also contribute

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slightly to the atomic mass, and because of the nuclear binding energy. For example, the mass of 19F is 18.9984032u. The only exception to the atomic mass of an isotope not being a natural number is 12C, which has a mass ofexactly 12, because u is defined as 1/12th of the mass of a free carbon-12 atom.

IsotopesIsotopes are atoms of the same element (that is, with the same number of protons in their atomic nucleus), but havingdifferent numbers of neutrons. Most (66 of 94) naturally occurring elements have more than one stable isotope. Thus,for example, there are three main isotopes of carbon. All carbon atoms have 6 protons in the nucleus, but they canhave either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, the three isotopes ofcarbon are known as carbon-12, carbon-13, and carbon-14, often abbreviated to 12C, 13C, and 14C. Carbon ineveryday life and in chemistry is a mixture of 12C, 13C, and 14C atoms.Except in the case of the isotopes of hydrogen (which differ greatly from each other in relative mass—enough tocause chemical effects), the isotopes of the various elements are typically chemically nearly indistinguishable fromeach other. For example, the three naturally occurring isotopes of carbon have essentially the same chemicalproperties, but different nuclear properties. In this example, carbon-12 and carbon-13 are stable atoms, but carbon-14is unstable; it is radioactive, undergoing beta decay into nitrogen-14.As illustrated by carbon, all of the elements have some isotopes that are radioactive (radioisotopes), which decay intoother elements upon radiating an alpha or beta particle. Certain elements only have radioactive isotopes: specificallythe elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), andall observed elements with atomic numbers greater than 82.Of the 80 elements with at least one stable isotope, 26 have only one stable isotope, and the mean number of stableisotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes that occurfor an element is 10 (for tin, element 50).

AllotropesAtoms of pure elements may bond to each other chemically in more than one way, allowing the pure element to existin multiple structures (spacial arrangements of atoms), known as allotropes, which differ in their properties. Forexample, carbon can be found as diamond, which has a tetrahedral structure around each carbon atom; graphite,which has layers of carbon atoms with a hexagonal structure stacked on top of each other; graphene, which is asingle layer of graphite that is incredibly strong; fullerenes, which have nearly spherical shapes; and carbonnanotubes, which are tubes with a hexagonal structure (even these may differ from each other in electricalproperties). The ability for an element to exist in one of many structural forms is known as 'allotropy'.

Standard stateThe standard state, or reference state, of an element is defined as its thermodynamically most stable state at 1 bar at agiven temperature (typically at 298.15 K). In thermochemistry, an element is defined to have an enthalpy offormation of zero in its standard state. For example, the reference state for carbon is graphite, because it is morestable than the other allotropes.

NomenclatureThe naming of elements precedes the atomic theory of matter, although at the time it was not known which chemicals were elements and which compounds. When it was learned, existing names (e.g., gold, mercury, iron) were kept in most countries, and national differences emerged over the names of elements either for convenience, linguistic niceties, or nationalism. For example, the Germans use "Wasserstoff" for "hydrogen", "Sauerstoff" for "oxygen" and "Stickstoff" for "nitrogen", while English and some romance languages use "sodium" for "natrium"

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and "potassium" for "kalium", and the French, Italians, Greeks, Portuguese and Poles prefer "azote/azot/azoto" for"nitrogen".But for international trade, the official names of the chemical elements both ancient and recent are decided by theInternational Union of Pure and Applied Chemistry, which has decided on a sort of international English language.That organization has recently prescribed that "aluminium" and "caesium" take the place of the US spellings"aluminum" and "cesium", while the US "sulfur" takes the place of the British "sulphur". Chemicals that are practicalto sell in bulk in many countries, however, still have national names, and those that do not use the Latin alphabetcannot be expected to use the IUPAC name.According to IUPAC, the full name of an element is not capitalized, even if it is derived from a proper noun such asthe elements californium or einsteinium (unless it would be capitalized by some other rule, such as to begin asentence). Isotopes of chemical elements are also uncapitalized if written out: carbon-12 or uranium-235. Symbols ofchemical elements, however, are capitalized: thus the symbols for the elements just discussed are Cf and Es; C-12and U-235.In the second half of the twentieth century physics laboratories became able to produce nuclei of chemical elementsthat have a half life too short for them to remain in any appreciable amounts. These are also named by IUPAC,which generally adopts the name chosen by the discoverer. This can lead to the controversial question of whichresearch group actually discovered an element, a question that delayed naming of elements with atomic number of104 and higher for a considerable time. (See element naming controversy).Precursors of such controversies involved the nationalistic namings of elements in the late nineteenth century. Forexample, lutetium was named in reference to Paris, France. The Germans were reluctant to relinquish naming rightsto the French, often calling it cassiopeium. The British discoverer of niobium originally named it columbium, inreference to the New World. It was used extensively as such by American publications prior to internationalstandardization.

Chemical symbolsFor the listing of current and not used Chemical symbols, and other symbols that look like chemical symbols,please see List of elements by symbol.

Specific chemical elementsBefore chemistry became a science, alchemists had designed arcane symbols for both metals and commoncompounds. These were however used as abbreviations in diagrams or procedures; there was no concept of atomscombining to form molecules. With his advances in the atomic theory of matter, John Dalton devised his ownsimpler symbols, based on circles, which were to be used to depict molecules.The current system of chemical notation was invented by Berzelius. In this typographical system chemical symbolsare not used as mere abbreviations - though each consists of letters of the Latin alphabet - they are symbols intendedto be used by peoples of all languages and alphabets. The first of these symbols were intended to be fully universal;since Latin was the common language of science at that time, they were abbreviations based on the Latin names ofmetals - Cu comes from Cuprum, Fe comes from Ferrum, Ag from Argentum. The symbols were not followed by aperiod (full stop) as abbreviations were. Later chemical elements were also assigned unique chemical symbols, basedon the name of the element, but not necessarily in English. For example, sodium has the chemical symbol 'Na' afterthe Latin natrium. The same applies to "W" (wolfram) for tungsten, "Fe" (ferrum) for Iron, "Hg" (hydrargyrum) formercury, "Sn" (stannum) for tin, "K" (kalium) for potassium, "Au" (aurum) for gold, "Ag" (argentum) for silver,"Pb" (plumbum) for lead, and "Sb" (stibium) for antimony.Chemical symbols are understood internationally when element names might need to be translated. There are sometimes differences; for example, the Germans have used "J" instead of "I" for iodine, so the character would not

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be confused with a roman numeral.The first letter of a chemical symbol is always capitalized, as in the preceding examples, and the subsequent letters,if any, are always lower case (small letters).

General chemical symbolsThere are also symbols for series of chemical elements, for comparative formulas. These are one capital letter inlength, and the letters are reserved so they are not permitted to be given for the names of specific elements. Forexample, an "X" is used to indicate a variable group amongst a class of compounds (though usually a halogen), while"R" is used for a radical, meaning a compound structure such as a hydrocarbon chain. The letter "Q" is reserved for"heat" in a chemical reaction. "Y" is also often used as a general chemical symbol, although it is also the symbol ofyttrium. "Z" is also frequently used as a general variable group. "L" is used to represent a general ligand in inorganicand organometallic chemistry. "M" is also often used in place of a general metal.

Isotope symbolsThe three main isotopes of the element hydrogen are often written as H for protium, D for deuterium and T fortritium. This is in order to make it easier to use them in chemical equations, as it replaces the need to write out themass number for each atom. E.g. the formula for heavy water may be written D2O instead of ²H2O.

The periodic tableThe periodic table of the chemical elements is a tabular method of displaying the chemical elements. Althoughprecursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869.Mendeleev intended the table to illustrate recurring ("periodic") trends in the properties of the elements. The layoutof the table has been refined and extended over time, as new elements have been discovered, and new theoreticalmodels have been developed to explain chemical behavior.The periodic table is now ubiquitous within the academic discipline of chemistry, providing an extremely usefulframework to classify, systematize and compare all the many different forms of chemical behavior. The table hasalso found wide application in physics, biology, engineering, and industry. The current standard table contains 118confirmed elements as of April 10, 2010.

AbundanceDuring the early phases of the Big Bang, nucleosynthesis of hydrogen nuclei resulted in the production of hydrogenand helium isotopes, as well as very minuscule amounts (on the order of 10−10) of lithium and beryllium. There isargument about whether or not some boron was produced in the Big Bang, as it has been observed in some veryyoung stars,[13] but no heavier elements than boron were produced. As a result, the primordial abundance of atomsconsisted of roughly 75% 1H, 25% 4He, and 0.01% deuterium.[14] Subsequent enrichment of galactic halos occurreddue to Stellar nucleosynthesis and Supernova nucleosynthesis.[15] However intergalactic space can still closelyresemble the primordial abundance, unless it has been enriched by some means.The following graph (note log scale) shows abundance of elements in our solar system. The table shows the twelvemost common elements in our galaxy (estimated spectroscopically), as measured in parts per million, by mass.[16]

Nearby galaxies that have evolved along similar lines have a corresponding enrichment of elements heavier thanhydrogen and helium. The more distant galaxies are being viewed as they appeared in the past, so their abundancesof elements appear closer to the primordial mixture. As physical laws and processes appear common throughout thevisible universe, however, it is expected that these galaxies will likewise have evolved similar abundances ofelements.

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Abundances of the chemical elements in the Solar system.

Element Parts permillionby mass

Hydrogen 739,000

Helium 240,000

Oxygen 10,400

Carbon 4,600

Neon 1,340

Iron 1,090

Nitrogen 960

Silicon 650

Magnesium 580

Sulfur 440

Potassium 210

Nickel 100

Recently discovered elementsThe first transuranium element (element with atomic number greater than 92) discovered was neptunium in 1940. Asof February 2010, only the elements up to 112, copernicium, have been confirmed as discovered by IUPAC, whilemore or less reliable claims have been made for synthesis of elements 113, 114, 115, 116 and 118. The discovery ofelement 112 was acknowledged in 2009, and the name 'copernicium' and the atomic symbol 'Cn' were suggested forit.[17] The name and symbol were officially endorsed by IUPAC on February 19, 2010.[18] The heaviest element thatis believed to have been synthesized to date is element 118, ununoctium, on October 9, 2006, by the FlerovLaboratory of Nuclear Reactions in Dubna, Russia.[19] [20]

Element 117, ununseptium, has been synthesised[21] , and its place in the periodic table is preestablished.On April 24, 2008, Amnon Marinov and six other researchers claimed that element 122 has been detected in purifiednatural thorium.[22] [23] If confirmed, this would be the first naturally occurring heavy element discovered in morethan 50 years. It has yet to be proved as it is still under confirmation by the university but could be a majordevelopment as previously all transuranic elements were artificial. The claim of Marinov et al. was criticized by apart of the scientific community, and Marinov says he has submitted the article to the journals Nature and NaturePhysics but both turned it down without sending it for peer review.[24]

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See also• Abundance of the chemical elements• Compound• Chemical symbol• Chemistry• Discovery of the chemical elements• Elements song• Fictional element• Goldschmidt classification• Island of stability• List of chemical element name etymologies• List of elements by atomic number• List of elements by name• Periodic table• Systematic element name• Prices of elements and their compounds

Further reading• E.R. Scerri, The Periodic Table, Its Story and Its Significance, Oxford University Press, NY, 2007.

External links• Videos for each element [25] by the University of Nottingham

References[1] International Union of Pure and Applied Chemistry. " (http:/ / goldbook. iupac. org/ C01022. html)". Compendium of Chemical Terminology

Internet edition.[2] A. Earnshaw, Norman Greenwood (1997). Chemistry of the Elements (2 ed.). Butterworth-Heinemann.[3] http:/ / books. google. com/ books?id=xSjvowNydN8C& lpg=PP1& ots=eRla--Y6Ul& dq=Plato%20timaeus& pg=PA45#v=onepage&

q=cube& f=false[4] Hillar, Marian (2004). "The Problem of the Soul in Aristotle's De anima" (http:/ / www. socinian. org/ aristotles_de_anima. html). NASA

WMAP. . Retrieved 2006-08-10.[5] Partington, J.R. (1937). A Short History of Chemistry. New York: Dover Publications, Inc.. ISBN 0486659771.[6] Boyle, Robert (1661). The Sceptical Chymist. London. ISBN 0922802904.[7] Lavoisier, Antoine Laurent (1790). Elements of chemistry translated by Robert Kerr (http:/ / books. google. com/ ?id=4BzAjCpEK4gC&

pg=PA175). Edinburgh. pp. 175–176. ISBN 9780415179140. .[8] Carey, George, W. (1914). The Chemistry of Human Life. Los Angeles. ISBN 0766128407.[9] http:/ / www. nytimes. com/ 2010/ 04/ 07/ science/ 07element. html?hp[10] Gaitskell, R; Utyonkov, V. K.; Lobanov, Yu. V.; Abdullin, F. Sh.; Polyakov, A. N.; Sagaidak, R. N.; Shirokovsky, I. V.; Tsyganov, Yu. S. et

al. (2006). "Evidence for Dark Matter" (http:/ / gaitskell. brown. edu/ physics/ talks/ 0408_SLAC_SummerSchool/Gaitskell_DMEvidence_v16. pdf) (PDF). Physical Review C 74: timeline on page 10. doi:10.1103/PhysRevC.74.044602. . Retrieved2008-10-08.

[11] Sanderson, Katherine (17 October 2006). "Heaviest element made - again" (http:/ / www. nature. com/ news/ 2006/ 061016/ full/ 061016-4.html). [email protected]. Nature. . Retrieved 2006-10-19.

[12] Phil Schewe and Ben Stein (17 October 2006). "Elements 116 and 118 Are Discovered" (http:/ / www. aip. org/ pnu/ 2006/ 797. html).Physics News Update. American Institute of Physics. . Retrieved 2006-10-19.

[13] Hubble Observations Bring Some Surprises - New York Times (http:/ / query. nytimes. com/ gst/ fullpage.html?res=9E0CE5D91F3AF937A25752C0A964958260)

[14] Wright, Edward L. (September 12, 2004). "Big Bang Nucleosynthesis" (http:/ / www. astro. ucla. edu/ ~wright/ BBNS. html). UCLADivision of Astronomy. . Retrieved 2007-02-22.

[15] G. Wallerstein, I. Iben Jr., P. Parker, A. M. Boesgaard, G. M. Hale, A. E. Champagne, C. A. Barnes, F. KM-dppeler, V. V. Smith, R. D. Hoffman, F. X. Timmes, C. Sneden, R.N. Boyd, B.S. Meyer, D.L. Lambert (1999). "Synthesis of the elements in stars: forty years of progress"

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(http:/ / www. cococubed. com/ papers/ wallerstein97. pdf) (pdf). Reviews of Modern Physics 69 (4): 995–1084.doi:10.1103/RevModPhys.69.995. . Retrieved 2006-08-04.

[16] Croswell, Ken (February 1996). Alchemy of the Heavens (http:/ / kencroswell. com/ alchemy. html). Anchor. ISBN 0-385-47214-5. .[17] "IUPAC Announces Start of the Name Approval Process for the Element of Atomic Number 112" (http:/ / media. iupac. org/ news/

112_Naming_Process_20090720. pdf). 20 July 2009. . Retrieved 2009-08-27.[18] IUPAC (International Union of Pure and Applied Chemistry): Element 112 is Named Copernicium (http:/ / www. iupac. org/ web/ nt/

2010-02-20_112_Copernicium)[19] Phil Schewe and Ben Stein (17 October 2006). "Elements 116 and 118 Are Discovered" (http:/ / www. aip. org/ pnu/ 2006/ 797. html).

Physics News Update. American Institute of Physics. . Retrieved 2006-10-19.[20] Oganessian, Yu. Ts. et al.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Sagaidak, R.; Shirokovsky, I.; Tsyganov, Yu. et al.

(2006-10-09). "Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm+48Ca fusion reactions". Physical Review C 74 (4):044602. doi:10.1103/PhysRevC.74.044602.

[21] http:/ / www. jinr. ru/ img_sections/ PAC/ NP/ 31/ PAK_NP_31_recom_eng. pdf[22] Marinov, A.; Rodushkin, I.; Kolb, D.; Pape, A.; Kashiv, Y.; Brandt, R.; Gentry, R. V.; Miller, H. W. (2008). "Evidence for a long-lived

superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th" (http:/ / arxiv. org/ abs/ 0804. 3869).ArXiv.org 74: 044602. doi:10.1103/PhysRevC.74.044602. . Retrieved 2008-04-28.

[23] Battersby, Stephen (2008-05-02). "Has the heaviest element been found?" (http:/ / www. newscientist. com/ article/dn13828-has-the-heaviest-element-been-found. html). NewScientist. . Retrieved 2009-05-01.

[24] Van Noorden, Richard (2008-05-02). "Heaviest element claim criticised" (http:/ / www. rsc. org/ chemistryworld/ News/ 2008/ May/02050802. asp). Chemistry World (Royal Society of Chemistry). . Retrieved 2009-05-01.

[25] http:/ / periodicvideos. com/

IsotopeIsotopes are different types of atoms (nuclides) of the same chemical element, each having a different number ofneutrons. In a corresponding manner, isotopes differ in mass number (or number of nucleons) but never in atomicnumber.[1] The number of protons (the atomic number) is the same because that is what characterizes a chemicalelement. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with massnumbers 12, 13 and 14, respectively. The atomic number of carbon is 6, so the neutron numbers in these isotopes ofcarbon are therefore 12−6 = 6, 13−6 = 7, and 14–6 = 8, respectively.A nuclide is an atomic nucleus with a specified composition of protons and neutrons. The nuclide conceptemphasizes nuclear properties over chemical properties, while the isotope concept emphasizes chemical overnuclear. The neutron number has drastic effects on nuclear properties, but negligible effects on chemical properties.Since isotope is the older term, it is better known, and is still sometimes used in contexts where nuclide might bemore appropriate, such as nuclear technology.An isotope and/or nuclide is specified by the name of the particular element (this indicates the atomic numberimplicitly) followed by a hyphen and the mass number (e.g. helium-3, carbon-12, carbon-13, iodine-131 anduranium-238). When a chemical symbol is used, e.g., "C" for carbon, standard notation is to indicate the number ofnucleons with a superscript at the upper left of the chemical symbol and to indicate the atomic number with asubscript at the lower left (e.g. 32He, 42He, 12

6C, 146C, 235

92U, and 23992U).

Some isotopes are radioactive and are therefore described as radioisotopes or radionuclides, while others have neverbeen observed to undergo radioactive decay and are described as stable isotopes. For example, 14C is a radioactiveform of carbon while 12C and 13C are stable isotopes. There are about 339 naturally occurring nuclides on Earth[2] ,of which 288 are primordial nuclides. These include 31 nuclides with very long half lives (over 80 million years) and257 which are formally considered as "stable"[2] . About 30 of these "stable" isotopes have actually been observed todecay, but with half lives too long to be estimated so far. This leaves 227 nuclides that have not been observed todecay at all.Many more apparently "stable" isotopes are predicted by theory to be radioactive, with extremely long half-lives (this does not count the posibility of proton decay, which would make all nuclides unstable). Of the 227 nuclides never observed to decay, only 90 of these (all from the first 40 elements) are stable in theory to all known forms of

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Isotope 28

decay. Element 41 (niobium) is theoretically unstable to spontaneous fission, but this has never been detected. Manyother stable nuclides are in theory energetically susceptible to other known forms of decay such as alpha decay ordouble beta decay, but no decay has yet been observed. The half lives for these processes often exceed a milliontimes the estimated age of the universe.Adding in the radioactive nuclides that have been created artificially, there are more than 3100 currently knownnuclides.[3] . These include 905 nuclides which are either stable, or have half lives longer than 60 minutes. See list ofnuclides for details.

History of the term

In the bottom right corner of JJ Thomson'sphotographic plate are the separate impact marks

for the two isotopes of neon: neon-20 andneon-22.

The term isotope was coined in 1913 by Margaret Todd, a Scottishphysician, during a conversation with Frederick Soddy (to whom shewas distantly related by marriage).[4] Soddy, a chemist at GlasgowUniversity, explained that it appeared from his investigations as if eachposition in the periodic table was occupied by multiple entities. HenceTodd made the suggestion, which Soddy adopted, that a suitable namefor such an entity would be the Greek term for "at the same place".

Soddy's own studies were of radioactive (unstable) atoms. The firstobservation of different stable isotopes for an element was by J. J.Thomson in 1913. As part of his exploration into the composition ofcanal rays, Thomson channeled streams of neon ions through amagnetic and an electric field and measured their deflection by placinga photographic plate in their path. Each stream created a glowing patchon the plate at the point it struck. Thomson observed two separatepatches of light on the photographic plate (see image), which suggestedtwo different parabolas of deflection. Thomson eventually concludedthat some of the atoms in the neon gas were of higher mass than therest. F.W. Aston subsequently discovered different stable isotopes fornumerous elements using a mass spectrograph.

Variation in properties between isotopes

Chemical and molecular propertiesA neutral atom has the same number of electrons as protons. Thus, different isotopes of a given element all have thesame number of protons and electrons and share a similar electronic structure. Because the chemical behavior of anatom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behavior.The main exception to this is the kinetic isotope effect: due to their larger masses, heavier isotopes tend to reactsomewhat more slowly than lighter isotopes of the same element. This is most pronounced for protium (1H) anddeuterium (2H), because deuterium has twice the mass of protium. The mass effect between deuterium and therelatively light protium also affects the behavior of their respective chemical bonds, by means of changing the centerof gravity (reduced mass) of the atomic systems. However, for heavier elements, which have more neutrons thanlighter elements, the ratio of the nuclear mass to the collective electronic mass is far greater, and the relative massdifference between isotopes is much less. For these two reasons, the mass-difference effects on chemistry are usuallynegligible.

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Isotope 29

Isotope half lifes. Note that the plot for stable isotopes diverges from the line,protons Z = neutrons N as the element number Z becomes larger

In similar manner, two molecules that differonly in the isotopic nature of their atoms(isotopologues) will have identicalelectronic structure and therefore almostindistinguishable physical and chemicalproperties (again with deuterium providingthe primary exception to this rule). Thevibrational modes of a molecule aredetermined by its shape and by the massesof its constituent atoms. As a consequence,isotopologues will have different sets ofvibrational modes. Since vibrational modesallow a molecule to absorb photons ofcorresponding energies, isotopologues havedifferent optical properties in the infraredrange.

Nuclear properties and stability

Atomic nuclei consist of protons andneutrons bound together by the residualstrong force. Because protons are positivelycharged, they repel each other. Neutrons,which are electrically neutral, stabilize thenucleus in two ways. Their copresencepushes protons slightly apart, reducing the electrostatic repulsion between the protons, and they exert the attractivenuclear force on each other and on protons. For this reason, one or more neutrons are necessary for two or moreprotons to be bound into a nucleus. As the number of protons increases, so does the ratio of neutrons to protonsnecessary to ensure a stable nucleus (see graph at right). For example, although the neutron:proton ratio of 3

2He is1:2, the neutron:proton ratio of 238

92U is greater than 3:2. A number of lighter elements have stable nuclides with theratio 1:1 (Z = N). The nuclide 40

20Ca (calcium-40) is the heaviest stable nuclide with the same number of neutronsand protons; all heavier stable nuclides contain more neutrons than protons.

Numbers of isotopes per elementOf the 80 elements with a stable isotope, the largest number of stable isotopes observed for any element is ten (forthe element tin). Xenon is the only element that has nine stable isotopes. Cadmium has eight stable isotopes. Fiveelements have seven stable isotopes, eight have six stable isotopes, ten have five stable isotopes, eight have fourstable isotopes, nine have three stable isotopes, 16 have two stable isotopes (counting 180m

73Ta as stable), and 26elements have only a single stable isotope (of these, 19 are so-called mononuclidic elements, having a singleprimordial stable isotope that dominates and fixes the atomic weight of the natural element to high precision; 3radioactive mononuclidic elements occur as well).[5] In total, there are 257 nuclides that have not been observed todecay. For the 80 elements that have one or more stable isotopes, the average number of stable isotopes is 257/80 =3.2 isotopes per element.

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Isotope 30

Even and odd nucleon numbers

Even/odd N

Mass E O All

Stable 145 101 246

Longlived 20 6 26

Primordial 165 107 272

The proton:neutron ratio is not the only factor affecting nuclear stability. Adding neutrons to isotopes can vary theirnuclear spins and nuclear shapes, causing differences in neutron capture cross-sections and gamma spectroscopy andnuclear magnetic resonance properties.

Even mass number

Beta decay of an even-even nucleus produces an odd-odd nucleus, and vice versa. An even number of protons or ofneutrons are more stable (lower binding energy) because of pairing effects, so even-even nuclei are much morestable than odd-odd. One effect is that there are few stable odd-odd nuclei, but another effect is to prevent beta decayof many even-even nuclei into another even-even nucleus of the same mass number but lower energy, because decayproceeding one step at a time would have to pass through an odd-odd nucleus of higher energy. This makes for alarger number of stable even-even nuclei, up to three for some mass numbers, and up to seven for some atomic(proton) numbers. Double beta decay directly from even-even to even-even skipping over an odd-odd nuclide is onlyoccasionally possible, and even then with a half-life greater than a billion times the age of the universe.Even-mass-number nuclides have integer spin and are bosons.

Even proton-even neutron

Even/odd Z, N

p,n EE OO EO OE

Stable 140 5 53 48

Longlived 16 4 2 4

Primordial 156 9 55 52

For example, the extreme stability of helium-4 due to a double pairing of 2 protons and 2 neutrons prevents anynuclides containing five or eight nucleons from existing for long enough to serve as platforms for the buildup ofheavier elements during fusion formation in stars (see triple alpha process).There are 141 stable even-even isotopes, forming 55% of the 257 stable isotopes. There are also 16 primordiallonglived even-even isotopes. As a result, many of the 41 even-numbered elements from 2 to 82 have manyprimordial isotopes. Half of these even-numbered elements have six or more stable isotopes.All even-even nuclides have spin 0 in their ground state.

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Isotope 31

Odd proton-odd neutron

Only five stable nuclides contain both an odd number of protons and an odd number of neutrons: the first fourodd-odd nuclides 21H, 63Li, 10

5B, and 147N (where changing a proton to a neutron or vice versa would lead to a very

lopsided proton-neutron ratio) and 180m73Ta, which has not yet been observed to decay despite experimental

attempts[6] . Also, four long-lived radioactive odd-odd nuclides (4019K, 50

23V, 13857La, 176

71Lu) occur naturally.Of these 9 primordial odd-odd nuclides, only 14

7N is the most common isotope of a common element, because it is apart of the CNO cycle; 6

3Li and 105B are minority isotopes of elements that are rare compared to other light

elements, while the other six isotopes make up only a tiny percentage of their elements.Few odd-odd nuclides (and none of the primordial ones) have spin 0 in the ground state.

Odd mass number

There is only one beta-stable nuclide per odd mass number because there is no difference in binding energy betweeneven-odd and odd-even comparable to that between even-even and odd-odd, and other nuclides of the same mass arefree to beta decay towards the lowest-energy one. For mass numbers 5, 147, 151, and 209 and up, the one beta-stableisobar is able to alpha decay, so that there are no stable isotopes with these mass numbers. This gives a total of 101stable isotopes with odd mass numbers.Odd-mass-number nuclides have half-integer spin and are fermions.

Odd proton-even neutron

These form most of the stable isotopes of the odd-numbered elements, but there is only one stable odd-even isotopefor each of the 41 odd-numbered elements from 1 to 81, except for technetium (43Tc) and promethium (61Pm) thathave no stable isotopes, and chlorine (17Cl), potassium (19K), copper (29Cu), gallium (31Ga), bromine (35Br), silver(47Ag), antimony (51Sb), iridium (Ir|BL=77), and thallium (81Tl), each of which has two, making a total of 48 stableodd-even isotopes. There are also four primordial long-lived odd-even isotopes, 87

37Rb, 11549In, 151

63Eu, and187

75Re.

Even proton-odd neutron

There are 54 stable isotopes that have an even number of protons and an odd number of neutrons. There are also fourprimordial long lived even-odd isotopes, 113

48Cd (beta decay, half-life is 7.7 × 1015 years); 14762Sm (1.06 × 1011a);

and 14962Sm (>2 × 1015a); and the fissile 235

92U.The only even-odd isotopes that are the most common one for their element are 195

78Pt and 94Be. Beryllium-9 is theonly stable beryllium isotope because the expected beryllium-8 has higher energy than two alpha particles andtherefore decays to them.

Odd neutron number

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Isotope 32

Even/odd N

n E O

Stable 188 58

Longlived 20 6

Primordial 208 64

The only odd-neutron-number isotopes that are the most common isotope of their element are 19578Pt, 9

4Be and14

7N.Actinides with odd neutron number are generally fissile, while those with even neutron number are generally not,though they are split when bombarded with fast neutrons.

Occurrence in natureElements are composed of one or more naturally occurring isotopes. The unstable (radioactive) isotopes are eitherprimordial, in which case they have persisted down to the present because their rate of decay is so slow (e.g.,uranium-238 and potassium-40), or they are postprimordial, created by cosmic ray bombardment as cosmogenicnuclides (e.g., tritium, carbon-14) or by the decay of a radioactive primordial isotope to a radioactive radiogenicnuclide daughter (e.g., uranium to radium).As discussed above, only 80 elements have any stable isotopes, and 26 of these have only one stable isotope. Thus,about two thirds of stable elements occur naturally on Earth in multiple stable isotopes, with the largest number ofstable isotopes for an element being ten, for tin (50Sn). There are about 94 elements found naturally on Earth (up toplutonium inclusive), though some are detected only in very tiny amounts, such as plutonium-244. Scientistsestimate that the elements that occur naturally on Earth (some only as radioisotopes) occur as 339 isotopes (nuclides)in total.[7] Only 257 of these naturally occurring isotopes are stable in the sense of either never having been observedto decay as of the present time (227 nuclides), or having been observed to decay but with a half life too long toestimate (30 nuclides). An additional 31 primordial nuclides (to a total of 288 primordial nuclides), are radioactivewith known half lives, but have half lives longer than 80 million years, allowing them to exist from the beginning ofthe solar system. See list of nuclides for details.All the known stable isotopes occur naturally on Earth; the other naturally occurring-isotopes are radioactive butoccur on Earth due to their relatively long half-lives, or else due to other means of ongoing natural production. Theseinclude the afore-mentioned cosmogenic nuclides and the short-lived radioisotopes formed by decay of a primordialradioactive isotope, such as radon and radium from uranium.An additional ~3000 radioactive isotopes not found in nature have been created in nuclear reactors and in particleaccelerators. Many short-lived isotopes not found naturally on Earth have also been observed by spectroscopicanalysis, being naturally created in stars or supernovae. An example is aluminum-26, which is not naturally found onEarth, but which is found in abundance on an astronomical scale.The tabulated atomic masses of elements are averages that account for the presence of multiple isotopes withdifferent masses. Before the discovery of isotopes, empirically determined noninteger values of atomic massconfounded scientists. For example, a sample of chlorine contains 75.8% chlorine-35 and 24.2% chlorine-37, givingan average atomic mass of 35.5 atomic mass units.According to generally accepted cosmology theory, only isotopes of hydrogen and helium, and traces of some isotopes of lithium and beryllium were created at the Big Bang, while all other isotopes were synthesized later, in stars and supernovae, and in interactions between energetic particles such as cosmic rays, and previously produced isotopes. (See nucleosynthesis for details of the various processes thought to be responsible for isotope production.) The respective abundances of isotopes on Earth result from the quantities formed by these processes, their spread through the galaxy, and the rates of decay for isotopes that are unstable. After the initial coalescence of the solar

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Isotope 33

system, isotopes were redistributed according to mass, and the isotopic composition of elements varies slightly fromplanet to planet. This sometimes makes it possible to trace the origin of meteorites.

Atomic mass of isotopesThe atomic mass (mr) of an isotope is determined mainly by its mass number (i.e. number of nucleons in its nucleus).Small corrections are due to the binding energy of the nucleus (see mass defect), the slight difference in massbetween proton and neutron, and the mass of the electrons associated with the atom, the latter because theelectron:nucleon ratio differs among isotopes.The mass number is a dimensionless quantity. The atomic mass, on the other hand, is measured using the atomicmass unit based on the mass of the carbon atom. It is denoted with symbols "u" (for unit) or "Da" (for Dalton).The atomic masses of naturally occurring isotopes of an element determine the atomic weight of the element. Whenthe element contains N isotopes, the equation below is applied for the atomic weight M:

where m1, m2, ..., mN are the atomic masses of each individual isotope, and x1, ... , xN are the relative abundances ofthese isotopes.

Applications of isotopesSeveral applications exist that capitalize on properties of the various isotopes of a given element. Isotope separationis a significant technological challenge, particularly with heavy elements such as uranium or plutonium. Lighterelements such as lithium, carbon, nitrogen, and oxygen are commonly separated by gas diffusion of their compoundssuch as CO and NO. The separation of hydrogen and deuterium is unusual since it is based on chemical rather thanphysical properties, for example in the Girdler sulfide process. Uranium isotopes have been separated in bulk by gasdiffusion, gas centrifugation, laser ionization separation, and (in the Manhattan Project) by a type of production massspectroscopy.

Use of chemical and biological properties• Isotope analysis is the determination of isotopic signature, the relative abundances of isotopes of a given element

in a particular sample. For biogenic substances in particular, significant variations of isotopes of C, N and O canoccur. Analysis of such variations has a wide range of applications, such as the detection of adulteration of foodproducts.[8] The identification of certain meteorites as having originated on Mars is based in part upon theisotopic signature of trace gases contained in them.[9]

• Another common application is isotopic labeling, the use of unusual isotopes as tracers or markers in chemicalreactions. Normally, atoms of a given element are indistinguishable from each other. However, by using isotopesof different masses, they can be distinguished by mass spectrometry or infrared spectroscopy. For example, in'stable isotope labeling with amino acids in cell culture (SILAC)' stable isotopes are used to quantify proteins. Ifradioactive isotopes are used, they can be detected by the radiation they emit (this is called radioisotopiclabeling).

• A technique similar to radioisotopic labeling is radiometric dating: using the known half-life of an unstableelement, one can calculate the amount of time that has elapsed since a known level of isotope existed. The mostwidely known example is radiocarbon dating used to determine the age of carbonaceous materials.

• Isotopic substitution can be used to determine the mechanism of a reaction via the kinetic isotope effect.

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Isotope 34

Use of nuclear properties• Several forms of spectroscopy rely on the unique nuclear properties of specific isotopes. For example, nuclear

magnetic resonance (NMR) spectroscopy can be used only for isotopes with a nonzero nuclear spin. The mostcommon isotopes used with NMR spectroscopy are 1H, 2D,15N, 13C, and 31P.

• Mössbauer spectroscopy also relies on the nuclear transitions of specific isotopes, such as 57Fe.• Radionuclides also have important uses. Nuclear power and nuclear weapons development require relatively large

quantities of specific isotopes.

See also• Atom• Table of nuclides• Radionuclide (or radioisotope)• Nuclear medicine (includes medical isotopes)• Isotopomer• List of particles• Isotopes are nuclides having the same number of protons; compare:

• Isotones are nuclides having the same number of neutrons.• Isobars are nuclides having the same mass number, i.e. sum of protons plus neutrons.• Nuclear isomers are different excited states of the same type of nucleus. A transition from one isomer to

another is accompanied by emission or absorption of a gamma ray, or the process of internal conversion. (Notto be confused with chemical isomers.)

• Bainbridge mass spectrometer

External links• Nucleonica Nuclear Science Portal [10]

• Nucleonica Nuclear Science Wiki [11]

• International Atomic Energy Agency [12]

• Atomic weights of all isotopes [13]

• Atomgewichte, Zerfallsenergien und Halbwertszeiten aller Isotope [14]

• Chart of the Nuclides [15] produced by the Knolls Atomic Power Laboratory $25• Exploring the Table of the Isotopes [16] at the LBNL• Current isotope research and information [17]

• Radioactive Isotopes [18] by the CDC• Interacive Chart of the nuclides, isotopes and Periodic Table [19]

• The LIVEChart of Nuclides - IAEA [20] with isotope data, in Java [20] or HTML [21]

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Isotope 35

References[1] IUPAC http:/ / goldbook. iupac. org/ I03331. html[2] "Radioactives Missing From The Earth" (http:/ / www. don-lindsay-archive. org/ creation/ isotope_list. html). .[3] "NuDat 2 Description" (http:/ / www. nndc. bnl. gov/ nudat2/ help/ index. jsp). .[4] Budzikiewicz H, Grigsby RD (2006). "Mass spectrometry and isotopes: a century of research and discussion". Mass spectrometry reviews 25

(1): 146–57. doi:10.1002/mas.20061. PMID 16134128.[5] Sonzogni, Alejandro. "Interactive Chart of Nuclides" (http:/ / www. nndc. bnl. gov/ chart/ ). National Nuclear Data Center: Brook haven

National Laboratory. .[6] hhttp://bryza.if.uj.edu.pl/zdfk/wp-includes/publications/misiaszek_180mTa_2009.pdf Search for the radioactivity of 180mTa using an

underground HPGe sandwich spectrometer, 2009[7] (http:/ / www. don-lindsay-archive. org/ creation/ isotope_list. html)[8] E. Jamin et al. (2003). "Improved Detection of Added Water in Orange Juice by Simultaneous Determination of the Oxygen-18/Oxygen-16

Isotope Ratios of Water and Ethanol Derived from Sugars"" (http:/ / pubs. acs. org/ cgi-bin/ article. cgi/ jafcau/ 2003/ 51/ i18/ pdf/ jf030167 m. pdf). J. Agric. Food Chem. 51: 5202. doi:10.1021/jf030167 m. .

[9] A. H. Treiman, J. D. Gleason and D. D. Bogard (2000). ""The SNC meteorites are from Mars"" (http:/ / www. sciencedirect. com/science?_ob=ArticleURL& _udi=B6V6T-41WBDHD-8& _user=2400262& _coverDate=10/ 31/ 2000& _alid=678948366& _rdoc=3&_fmt=summary& _orig=search& _cdi=5823& _sort=r& _docanchor=& view=c& _ct=89& _acct=C000057185& _version=1&_urlVersion=0& _userid=2400262& md5=c5ae2aa8ea60dbd76c2870048730a299). Planet. Space. Sci. 48: 1213.doi:10.1016/S0032-0633(00)00105-7. .

[10] http:/ / www. nucleonica. net[11] http:/ / www. nucleonica. net/ wiki/ index. php/ Special:Allpages/ Help:[12] http:/ / www. IAEA. org[13] http:/ / physics. nist. gov/ cgi-bin/ Compositions/ stand_alone. pl?ele=& ascii=html& isotype=some[14] http:/ / atom. kaeri. re. kr/[15] http:/ / www. chartofthenuclides. com/[16] http:/ / ie. lbl. gov/ education/ isotopes. htm[17] http:/ / www. isotope. info/[18] http:/ / www. bt. cdc. gov/ radiation/ isotopes/[19] http:/ / www. yoix. org/ elements. html[20] http:/ / www-nds. iaea. org/ livechart[21] http:/ / www-nds. iaea. org/ relnsd/ vcharthtml/ VChartHTML. html

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Orbital 36

OrbitalAn atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair ofelectrons in an atom.[1] This function can be used to calculate the probability of finding any electron of an atom inany specific region around the atom's nucleus. These functions may serve as three-dimensional graph of an electron’slikely location. The term may thus refer directly to the physical region defined by the function where the electron islikely to be.[2] Specifically, atomic orbitals are the possible quantum states of an individual electron in the collectionof electrons around a single atom, as described by the orbital function.Despite the obvious analogy to planets revolving around the Sun, electrons cannot be described as solid particles andso atomic orbitals rarely, if ever, resemble a planet's elliptical path. A more accurate analogy might be that of a largeand often oddly-shaped atmosphere (the electron), distributed around a relatively tiny planet (the atomic nucleus).Atomic orbitals exactly describe the shape of this atmosphere only when a single electron is present in an atom.When more electrons are added to a single atom, the additional electrons tend to more evenly fill in a volume ofspace around the nucleus so that the resulting collection (sometimes termed the atom’s “electron cloud” [3] ) tendstoward a generally spherical zone of probability describing where the atom’s electrons will be found.

Electron atomic and molecular orbitals. The chart of orbitals (left) is arranged byincreasing energy (see Madelung rule). Note that atomic orbits are functions of three

variables (two angles, and the distance from the nucleus, r). These images are faithful tothe angular component of the orbital, but not entirely representative of the orbital as a

whole.

The idea that electrons might revolvearound a compact nucleus with definiteangular momentum was convincinglyargued in 1913 by Niels Bohr,[4] andthe Japanese physicist HantaroNagaoka published an orbit-basedhypothesis for electronic behavior asearly as 1904.[5] However, it was notuntil 1926 that the solution of theSchrödinger equation forelectron-waves in atoms provided thefunctions for the modern orbitals.[6]

Because of the difference fromclassical mechanical orbits, the term"orbit" for electrons in atoms, has beenreplaced with the term orbital—a termfirst coined by chemist RobertMulliken in 1932.[7] Atomic orbitalsare typically described as “hydrogen-like” (meaning one-electron) wave functions over space, categorized by n, l, andm quantum numbers, which correspond to the electrons' energy, angular momentum, and an angular momentumdirection, respectively. Each orbital is defined by a different set of quantum numbers and contains a maximum oftwo electrons. The simple names s

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Orbital 37

Computed hydrogen atom orbital for n=6, l=0, m=0

orbital, p orbital, d orbital and forbital refer to orbitals with angularmomentum quantum number l = 0, 1, 2and 3 respectively. These namesindicate the orbital shape and are usedto describe the electron configurationsas shown on the right. They arederived from the characteristics of theirspectroscopic lines: sharp, principal,diffuse, and fundamental, the restbeing named in alphabetical order(omitting j).[8] [9]

From about 1920, even before theadvent of modern quantum mechanics,the aufbau principle (constructionprinciple) that atoms were built up ofpairs of electrons, arranged in simplerepeating patterns of increasing oddnumbers (1,3,5,7..), had been used byNiels Bohr and others to infer thepresence of something like atomicorbitals within the total electron configuration of complex atoms. In the mathematics of atomic physics, it is alsooften convenient to reduce the electron functions of complex systems into combinations of the simpler atomicorbitals. Although each electron in a multi-electron atom is not confined to one of the “one-or-two-electron atomicorbitals” in the idealized picture above, still the electron wave-function may be broken down into combinationswhich still bear the imprint of atomic orbitals; as though, in some sense, the electron cloud of a many-electron atomis still partly “composed” of atomic orbitals, each containing only one or two electrons. The physicality of this viewis best illustrated in the repetitive nature of the chemical and physical behavior of elements which results in thenatural ordering known from the 19th century as the periodic table of the elements. In this ordering, the repeatingperiodicity of 2, 6, 10, and 14 elements in the periodic table corresponds with the total number of electrons whichoccupy a complete set of s, p, d and f atomic orbitals, respectively.

Orbital namesOrbitals are given names in the form:

where X is the energy level corresponding to the principal quantum number n, type is a lower-case letter denotingthe shape or subshell of the orbital and it corresponds to the angular quantum number l, and y is the number ofelectrons in that orbital.For example, the orbital 1s2 (pronounced "one ess two") has two electrons and is the lowest energy level (n = 1) andhas an angular quantum number of l = 0. In X-ray notation, the principal quantum number is given a letter associatedwith it. For n = 1, 2, 3, 4, 5, ..., the letters associated with those numbers are K, L, M, N, O, ... respectively.

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Orbital 38

Formal quantum mechanical definitionIn quantum mechanics, the state of an atom, i.e. the eigenstates of the atomic Hamiltonian, is expanded (seeconfiguration interaction expansion and basis (linear algebra)) into linear combinations of anti-symmetrized products(Slater determinants) of one-electron functions. The spatial components of these one-electron functions are calledatomic orbitals. (When one considers also their spin component, one speaks of atomic spin orbitals.)In atomic physics, the atomic spectral lines correspond to transitions (quantum leaps) between quantum states of anatom. These states are labelled by a set of quantum numbers summarized in the term symbol and usually associatedto particular electron configurations, i.e. by occupations schemes of atomic orbitals (e.g. 1s2 2s2 2p6 for the groundstate of neon -- term symbol: 1S0).This notation means that the corresponding Slater determinants have a clear higher weight in the configurationinteraction expansion. The atomic orbital concept is therefore a key concept for visualizing the excitation processassociated to a given transition. For example, one can say for a given transition that it corresponds to the excitationof an electron from an occupied orbital to a given unoccupied orbital. Nevertheless one has to keep in mind thatelectrons are fermions ruled by Pauli exclusion principle and cannot be distinguished from the other electrons in theatom. Moreover, it sometimes happens that the configuration interaction expansion converges very slowly and thatone cannot speak about simple one-determinantal wave function at all. This is the case when electron correlation islarge.Fundamentally, an atomic orbital is a one-electron wavefunction, even though most electrons do not exist inone-electron atoms, and so the one-electron view is an approximation. When thinking about orbitals, we are oftengiven an orbital vision which (even if it is not spelled out) is heavily influenced by this Hartree–Fock approximation,which is one way to reduce the complexities of molecular orbital theory.

Connection to uncertainty relationImmediately after Heisenberg formulated his uncertainty relation, it was noted by Bohr that the existence of any sortof wave packet implies uncertainty in the wave frequency and wavelength, since a spread of frequencies is needed tocreate the packet itself. In quantum mechanics, where all particle momenta are associated with waves, it is theformation of such a wave packet which localizes the wave, and thus the particle, in space. In states where a quantummechanical particle is bound, it must be localized as a wave packet, and the existence of the packet and its minimumsize implies a spread and minimal value in particle wavelength, and thus also momentum and energy. In quantummechanics, as a particle is localized to a smaller region in space, the associated compressed wave packet requires alarger and larger range of momenta, and thus larger kinetic energy. Thus, the binding energy to contain or trap aparticle in a smaller region of space, increases without bound, as the region of space grows smaller. Particles cannotbe restricted to a geometric point in space, since this would require an infinite particle momentum.In chemistry, Schrödinger, Pauling, Mulliken and others noted that the consequence of Heisenberg's relation was thatthe electron, as a wave packet, could not be considered to have an exact location in its orbital. Max Born suggestedthat the electron's position needed to be described by a probability distribution which was connected with finding theelectron at some point in the wave-function which described its associated wave packet. The new quantummechanics did not give exact results, but only the probabilities for the occurrence of a variety of possible suchresults. Heisenberg held that the path of a moving particle has no meaning if we cannot observe it, as we cannot withelectrons in an atom.In the quantum picture of Heisenberg, Schrödinger and others, the Bohr atom number n for each orbital becameknown as an n-sphere in a three dimensional atom and was pictured as the mean energy of the probability cloud ofthe electron's wave packet which surrounded the atom.Although Heisenberg used infinite sets of positions for the electron in his matrices, this does not mean that theelectron could be anywhere in the universe. Rather there are several laws that show the electron must be in one

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Orbital 39

localized probability distribution. An electron is described by its energy in Bohr's atom which was carried over tomatrix mechanics. Therefore, an electron in a certain n-sphere had to be within a certain range from the nucleusdepending upon its energy. This restricts its location.

Hydrogen-like atomsThe simplest atomic orbitals are those that occur in an atom with a single electron, such as the hydrogen atom. In thiscase the atomic orbitals are the eigenstates of the hydrogen Hamiltonian. They can be obtained analytically (seehydrogen atom). An atom of any other element ionized down to a single electron is very similar to hydrogen, and theorbitals take the same form.For atoms with two or more electrons, the governing equations can only be solved with the use of methods ofiterative approximation. Orbitals of multi-electron atoms are qualitatively similar to those of hydrogen, and in thesimplest models, they are taken to have the same form. For more rigorous and precise analysis, the numericalapproximations must be used.A given (hydrogen-like) atomic orbital is identified by unique values of three quantum numbers: n, l, and ml. Therules restricting the values of the quantum numbers, and their energies (see below), explain the electronconfiguration of the atoms and the periodic table.The stationary states (quantum states) of the hydrogen-like atoms are its atomic orbital. However, in general, anelectron's behavior is not fully described by a single orbital. Electron states are best represented by time-depending"mixtures" (linear combinations) of multiple orbitals. See Linear combination of atomic orbitals molecular orbitalmethod.The quantum number n first appeared in the Bohr model where it determines the radius of each circular electronorbit. In modern quantum mechanics however, n determines the mean distance of the electron from the nucleus; allelectrons with the same value of n lie at the same average distance. For this reason, orbitals with the same value of nare said to comprise a "shell". Orbitals with the same value of n and also the same value of l are even more closelyrelated, and are said to comprise a "subshell".

Qualitative characterization

Limitations on the quantum numbersAn atomic orbital is uniquely identified by the values of the three quantum numbers, and each set of the threequantum numbers corresponds to exactly one orbital, but the quantum numbers only occur in certain combinations ofvalues. The rules governing the possible values of the quantum numbers are as follows:The principal quantum number n is always a positive integer. In fact, it can be any positive integer, but for reasonsdiscussed below, large numbers are seldom encountered. Each atom has, in general, many orbitals associated witheach value of n; these orbitals together are sometimes called electron shells.The azimuthal quantum number is a non-negative integer. Within a shell where n is some integer n0, rangesacross all (integer) values satisfying the relation . For instance, the n = 1 shell has only orbitalswith , and the n = 2 shell has only orbitals with , and . The set of orbitals associated with aparticular value of are sometimes collectively called a subshell.The magnetic quantum number is also always an integer. Within a subshell where is some integer , ranges thus: .The above results may be summarized in the following table. Each cell represents a subshell, and lists the values of

available in that subshell. Empty cells represent subshells that do not exist.

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1 2 3 4 ...

2 0 -1, 0,1

3 0 -1, 0,1

-2, -1, 0, 1, 2

4 0 -1, 0,1

-2, -1, 0, 1, 2 -3, -2, -1, 0, 1, 2, 3

5 0 -1, 0,1

-2, -1, 0, 1, 2 -3, -2, -1, 0, 1, 2, 3 -4, -3, -2 -1, 0, 1, 2, 3, 4

... ... ... ... ... ... ...

Subshells are usually identified by their - and -values. is represented by its numerical value, but isrepresented by a letter as follows: 0 is represented by 's', 1 by 'p', 2 by 'd', 3 by 'f', and 4 by 'g'. For instance, one mayspeak of the subshell with and as a '2s subshell'.

The shapes of orbitals

The shapes of the first five atomic orbitals: 1s, 2s, 2px,2py, and 2pz. The colorsshow the wavefunction phase.

Any discussion of the shapes of electronorbitals is necessarily imprecise, because agiven electron, regardless of which orbital itoccupies, can at any moment be found atany distance from the nucleus and in anydirection due to the uncertainty principle.

However, the electron is much more likelyto be found in certain regions of the atomthan in others. Given this, a boundary surface can be drawn so that the electron has a high probability to be foundanywhere within the surface, and all regions outside the surface have low values. The precise placement of thesurface is arbitrary, but any reasonably compact determination must follow a pattern specified by the behavior of , the square of the wavefunction. This boundary surface is what is meant when the "shape" of an orbital is referred to.Generally speaking, the number determines the size and energy of the orbital for a given nucleus: as increases,the size of the orbital increases. However, in comparing different elements, the higher nuclear charge Z of heavierelements causes their orbitals to contract by comparison to lighter ones, so that the overall size of the whole atomremains very roughly constant, even as the number of electrons in heavier elements (higher Z) increases.Also in general terms, determines an orbital's shape, and its orientation. However, since some orbitals aredescribed by equations in complex numbers, the shape sometimes depends on also.The single -orbitals ( ) are shaped like spheres. For n=1 the sphere is "solid" (it is most dense at the centerand fades exponentially outwardly), but for n=2 or more, each single s-orbital is composed of spherically symmetricsurfaces which are nested shells (i.e., the "wave-structure" is radial, following a sinusoidal radial component aswell). The -orbitals for all n numbers are the only orbitals with an anti-node (a region of high wave functiondensity) at the center of the nucleus. All other orbitals (p, d, f, etc.) have angular momentum, and thus avoid thenucleus (having a wave node at the nucleus).The three -orbitals for n=2 have the form of two ellipsoids with a point of tangency at the nucleus (sometimesreferred to as a dumbbell). The three -orbitals in each shell are oriented at right angles to each other, asdetermined by their respective linear combination of values of .

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Orbital 41

Four of the five -orbitals for n=3 look similar, each with four pear-shaped balls, each ball tangent to two others,and the centers of all four lying in one plane, between a pair of axes. Three of these planes are the -, -, and

-planes, and the fourth has the centres on the and axes. The fifth and final -orbital consists of threeregions of high probability density: a torus with two pear-shaped regions placed symmetrically on its axis.There are seven -orbitals, each with shapes more complex than those of the -orbitals.For each s, p, d, f and g set of orbitals, the set of orbitals which composes it forms a spherically symmetrical set ofshapes. For non-s orbitals, which have lobes, the lobes point in directions so as to fill space as symmetrically aspossible for number of lobes which exist for a set of orientations. For example, the three p orbitals have six lobeswhich are oriented to each of the six primary directions of 3-D space; for the 5 d orbitals, there are a total of 18lobes, in which again six point in primary directions, and the 12 additional lobes fill the 12 gaps which exist betweeneach pairs of these 6 primary axes.Additionally, as is the case with the s orbitals, individual p, d, f and g orbitals with n values higher than the lowestpossible value, exhibit an additional radial node structure which is reminiscent of harmonic waves of the same type,as compared with the lowest (or fundamental) mode of the wave. As with s orbitals, this phenomenon provides p, d,f, and g orbitals at the next higher possible value of n (for example, 3p orbitals vs. the fundamental 2p), an additionalnode in each lobe. Still higher values of n further increase the number of radial nodes, for each type of orbital.The shapes of atomic orbitals in one-electron atom are related to 3-dimensional spherical harmonics. These shapesare not unique, and any linear combination is valid, in fact it is possible to generate sets where all the d's are thesame shape, just like the px, py, and pz are the same shape.[10] [11]

Orbitals table

This table shows all orbital configurations for the real hydrogen-like wave functions up to 7s, and therefore coversthe simple electronic configuration for all elements in the periodic table up to radium. It is should also be noted thatthe pz orbital is the same as the p0 orbital, but the px and py are formed by taking linear compbinations of the p+1 andp-1 orbitals (which is why they are listed under the m=±1 label). Also, the p+1 and p-1 are not the same shape as thep0, since they are pure spherical harmonics.

s (l=0) p (l=1) d (l=2) f (l=3)

m=0 m=0 m=±1 m=0 m=±1 m=±2 m=0 m=±1 m=±2 m=±3

s pz

px

py d

z2 d

xzd

yzd

xy dx2

-y2 f

z3 f

xz2 f

yz2 f

xyz fz(x

2-y

2)

fx(x

2-3y

2)

fy(3x

2-y

2)

n=1

n=2

n=3

n=4

n=5 . . . . . . . . . . . . . . . . . . . . .

n=6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

n=7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Orbital 42

Orbital energyIn atoms with a single electron (hydrogen-like atoms), the energy of an orbital (and, consequently, of any electronsin the orbital) is determined exclusively by . The orbital has the lowest possible energy in the atom. Eachsuccessively higher value of has a higher level of energy, but the difference decreases as increases. For high , the level of energy becomes so high that the electron can easily escape from the atom.In atoms with multiple electrons, the energy of an electron depends not only on the intrinsic properties of its orbital,but also on its interactions with the other electrons. These interactions depend on the detail of its spatial probabilitydistribution, and so the energy levels of orbitals depend not only on but also on . Higher values of areassociated with higher values of energy; for instance, the 2p state is higher than the 2s state. When = 2, theincrease in energy of the orbital becomes so large as to push the energy of orbital above the energy of the s-orbital inthe next higher shell; when = 3 the energy is pushed into the shell two steps higher.The energy sequence of the first 24 subshells is given in the following table. Each cell represents a subshell with and given by its row and column indices, respectively. The number in the cell is the subshell's position in thesequence.

1 1

2 2 3

3 4 5 7

4 6 8 10 13

5 9 11 14 17 21

6 12 15 18 22 26

7 16 19 23 27 31

8 20 24 28 32 36

Note: empty cells indicate non-existent sublevels, while numbers in italics indicate sublevels that could exist, butwhich do not hold electrons in any element currently known.

Electron placement and the periodic tableSeveral rules govern the placement of electrons in orbitals (electron configuration). The first dictates that no twoelectrons in an atom may have the same set of values of quantum numbers (this is the Pauli exclusion principle).These quantum numbers include the three that define orbitals, as well as s, or spin quantum number. Thus, twoelectrons may occupy a single orbital, so long as they have different values of . However, only two electrons,because of their spin, can be associated with each orbital.Additionally, an electron always tends to fall to the lowest possible energy state. It is possible for it to occupy anyorbital so long as it does not violate the Pauli exclusion principle, but if lower-energy orbitals are available, thiscondition is unstable. The electron will eventually lose energy (by releasing a photon) and drop into the lowerorbital. Thus, electrons fill orbitals in the order specified by the energy sequence given above.This behavior is responsible for the structure of the periodic table. The table may be divided into several rows (called'periods'), numbered starting with 1 at the top. The presently known elements occupy seven periods. If a certainperiod has number , it consists of elements whose outermost electrons fall in the th shell.The periodic table may also be divided into several numbered rectangular 'blocks'. The elements belonging to a given block have this common feature: their highest-energy electrons all belong to the same -state (but the associated with that -state depends upon the period). For instance, the leftmost two columns constitute the 's-block'. The

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outermost electrons of Li and Be respectively belong to the 2s subshell, and those of Na and Mg to the 3s subshell.The number of electrons in a neutral atom increases with the atomic number. The electrons in the outermost shell, orvalence electrons, tend to be responsible for an element's chemical behavior. Elements that contain the same numberof valence electrons can be grouped together and display similar chemical properties.

Relativistic effectsFor elements with high atomic number Z, the effects of relativity become more pronounced, and especially so for selectrons, which move at relativistic velocities as they penetrate the screening electrons near the core of high Zatoms. This relativistic increase in momentum for high speed electrons causes a corresponding decrease inwavelength and contraction of 6s orbitals relative to 5d orbitals (by comparison to corresponding s and d electrons inlighter elements in the same column of the periodic table); this results in 6s valence electrons becoming lowered inenergy.Examples of significant physical outcomes of this effect include the lowered melting temperature of mercury (whichresults from 6s electrons not being available for metal bonding) and the golden color of gold and caesium (whichresults from narrowing of 6s to 5d transition energy to the point that visible light begins to be absorbed). See [12].In the Bohr Model, an electron has a velocity given by , where Z is the atomic number, is thefine-structure constant, and c is the speed of light. In non-relativistic quantum mechanics, therefore, any atom withan atomic number greater than 137 would require its 1s electrons to be traveling faster than the speed of light. Evenin the Dirac equation, which accounts for relativistic effects, the wavefunction of the electron for atoms with Z >137 is oscillatory and unbound. The significance of element 137, also known as untriseptium, was first pointed outby the physicist Richard Feynman. Element 137 is sometimes informally called feynmanium (symbol Fy). However,Feynman's approximation fails to predict the exact critical value of Z due to the non-point-charge nature of thenucleus and very small orbital radius of inner electrons, resulting in a potential seen by inner electrons which iseffectively less than Z. The critical Z value which makes the atom unstable with regard to high-field breakdown ofthe vacuum and production of electron-positron pairs, does not occur until Z is about 173. These conditions are notseen except transiently in collisions of very heavy nuclei such as lead or uranium in accelerators, where suchelectron-positron production from these effects has been claimed to be observed. See Extension of the periodic tablebeyond the seventh period.

See also• Atomic electron configuration table• Electron configuration• Energy level• List of Hund's rules• Molecular orbital• Quantum chemistry computer programs

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Further reading• Tipler, Paul; Ralph Llewellyn (2003). Modern Physics (4 ed.). New York: W. H. Freeman and Company.

ISBN 0-7167-4345-0.• Scerri, Eric (2007). The Periodic Table, Its Story and Its Significance. New York: Oxford University Press.

ISBN 978-0-19-530573-9.

External links• Guide to atomic orbitals [13]

• Covalent Bonds and Molecular Structure [14]

• Animation of the time evolution of an hydrogenic orbital [15]

• The Orbitron [16], a visualization of all common and uncommon atomic orbitals, from 1s to 7g• Grand table [17] Still images of many orbitals• David Manthey's Orbital Viewer [18] renders orbitals with n ≤ 30• Java orbital viewer applet [19]

• What does an atom look like? Orbitals in 3D [20]

• Atom Orbitals v.1.5 visualization software [21]

References[1] Milton Orchin,Roger S. Macomber, Allan Pinhas, and R. Marshall Wilson(2005)" Atomic Orbital Theory (http:/ / media. wiley. com/

product_data/ excerpt/ 81/ 04716802/ 0471680281. pdf)"[2] Daintith, J. (2004). Oxford Dictionary of Chemistry. New York: Oxford University Press. ISBN 0-19-860918-3.[3] The Feynman Lectures on Physics -The Definitive Edition, Vol 1 lect 6 pg 11. Feynman, Richard; Leighton; Sands. (2006) Addison Wesley

ISBN 0-8053-9046-4[4] Bohr, Niels (1913). "On the Constitution of Atoms and Molecules". Philosophical Magazine 26 (1): 476.[5] Nagaoka, Hantaro (May 1904). "Kinetics of a System of Particles illustrating the Line and the Band Spectrum and the Phenomena of

Radioactivity" (http:/ / www. chemteam. info/ Chem-History/ Nagaoka-1904. html). Philosophical Magazine 7: 445–455. .[6] Bryson, Bill (2003). A Short History of Nearly Everything. Broadway Books. pp. 141–143. ISBN 0-7679-0818-X.[7] Mulliken, Robert S. (July 1932). "Electronic Structures of Polyatomic Molecules and Valence. II. General Considerations" (http:/ / prola. aps.

org/ abstract/ PR/ v41/ i1/ p49_1). Phys. Rev. 41 (1): 49–71. doi:10.1103/PhysRev.41.49. .[8] Griffiths, David (1995). Introduction to Quantum Mechanics. Prentice Hall. pp. 190–191. ISBN 0-13-124405-1.[9] Levine, Ira (2000). Quantum Chemistry (5 ed.). Prentice Hall. pp. 144–145. ISBN 0-13-685512-1.[10] Powell, Richard E. (1968). "The five equivalent d orbitals". Journal of Chemical Education 45: 45. doi:10.1021/ed045p45.[11] Kimball, George E. (1940). "Directed Valence". The Journal of Chemical Physics 8: 188. doi:10.1063/1.1750628.[12] http:/ / www. chem1. com/ acad/ webtut/ atomic/ qprimer/ #Q26[13] http:/ / www. chemguide. co. uk/ atoms/ properties/ atomorbs. html[14] http:/ / wps. prenhall. com/ wps/ media/ objects/ 602/ 616516/ Chapter_07. html[15] http:/ / strangepaths. com/ atomic-orbital/ 2008/ 04/ 20/ en/[16] http:/ / www. shef. ac. uk/ chemistry/ orbitron/[17] http:/ / www. orbitals. com/ orb/ orbtable. htm[18] http:/ / www. orbitals. com/ orb/ index. html[19] http:/ / www. falstad. com/ qmatom/[20] http:/ / www. hydrogenlab. de/ elektronium/ HTML/ einleitung_hauptseite_uk. html[21] http:/ / taras-zavedy. narod. ru/ PROGRAMMS/ ATOM_ORBITALS_v_1_5_ENG/ Atom_Orbitals_v_1_5_ENG. html

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45

Groups

Group

The periodic table of the chemical elements

In chemistry, a group (also known as afamily) is a vertical column in theperiodic table of the chemicalelements. There are 18 groups in thestandard periodic table.

The modern explanation of the patternof the table is that the elements in agroup have similar configurations ofthe outermost electron shells of theiratoms: as most chemical properties aredominated by the orbital location ofthe outermost electron. There are threeconventional ways of numbering: Oneusing Arabic numerals, and two using Roman numerals. The Roman numeral names are the original traditionalnames of the groups; the Arabic numeral names are those recommended by the International Union of Pure andApplied Chemistry (IUPAC) to replace the old names in an attempt to reduce the confusion generated by the twoolder, but mutually confusing, schemes.

There is considerable confusion surrounding the two old systems in use (old IUPAC and CAS) that combined the useof Roman numerals with letters. In the old IUPAC system the letters A and B were designated to the left (A) andright (B) part of the table, while in the CAS system the letters A and B were designated to main group elements (A)and transition elements (B). The old IUPAC system was frequently used in Europe while the CAS was mostcommon in America. The new IUPAC scheme was developed to replace both systems as they confusingly used thesame names to mean different things. The IUPAC proposal was first circulated in 1985 for public comments,[1] andwas later included as part of the 1990 edition of the Nomenclature of Inorganic Chemistry.[2]

The periodic table groups are as follows (in the brackets are shown the old systems: European and American):• Group 1 (IA,IA): the alkali metals or lithium family• Group 2 (IIA,IIA): the alkaline earth metals or beryllium family• Group 3 (IIIA,IIIB): the scandium family• Group 4 (IVA,IVB): the titanium family• Group 5 (VA,VB): the vanadium family• Group 6 (VIA,VIB): the chromium family• Group 7 (VIIA,VIIB): the manganese family• Group 8 (VIII, VIIIB): the iron family• Group 9 (VIII, VIIIB): the cobalt family• Group 10 (VIII, VIIIB): the nickel family• Group 11 (IB,IB): the coinage metals (not an IUPAC-recommended name) or copper family• Group 12 (IIB,IIB): the zinc family• Group 13 (IIIB,IIIA): the boron family• Group 14 (IVB,IVA): the carbon family

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Group 46

• Group 15 (VB,VA): the pnictogens or nitrogen family• Group 16 (VIB,VIA): the chalcogens or oxygen family• Group 17 (VIIB,VIIA): the halogens or fluorine family• Group 18 (Group 0, VIIIA): the helium family/neon family; for the first six periods, these are the noble gases

References[1] Fluck, E. New notations in the periodic table. Pure & App. Chem. 1988, 60, 431-436. (http:/ / www. iupac. org/ publications/ pac/ 1988/ pdf/

6003x0431. pdf)[2] Leigh, G. J. Nomenclature of Inorganic Chemistry: Recommendations 1990. Blackwell Science, 1990. ISBN 0632024941.

3. Scerri, E. R. The Periodic Table, Its Story and Its Significance, Oxford University Press, 2007. ISBN978-0-19-530573-9.

Group IThe alkali metals are a series of chemical elements forming Group 1 (IUPAC style) of the periodic table: lithium(Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). (Hydrogen, although nominallyalso a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provideone of the best examples of group trends in properties in the periodic table, with well characterized homologousbehavior down the group.

PropertiesThe alkali metals are all highly reactive and are never found in elemental forms in nature. Because of this, they areusually stored immersed in mineral oil or kerosene (paraffin oil). They also tarnish easily and have low meltingpoints and densities.Physically, the alkali metals are mostly silver-colored, except for metallic caesium, which has a golden tint. Theseelements are all soft metals of low density. Chemically, all of the alkali metals react aggressively with the halogensto form ionic salts. They all react with water to form strongly alkaline hydroxides. The vigor of reaction increasesdown the group. All of the atoms of alkali metals have one electron in their outmost electron shells, hence their onlyway for achieving the equivalent of filled outmost electron shells is to give up one electron to an element with highelectronegativity, and hence to become singly charged positive ions, i.e. cations.When it comes to their nuclear physics, the elements potassium and rubidium are naturally weakly radioactivebecause they each contain a long half-life radioactive isotope.The element hydrogen, with its solitary one electron per atom, is usually placed at the top of Group 1 of the periodictable for convenience, but hydrogen is not counted as an alkali metal. Under typical conditions, pure hydrogen existsas a diatomic gas consisting of two atoms per molecule.The removal of the single electron of hydrogen requires considerably more energy than removal of the outer electronfrom the atoms of the alkali metals. As in the halogens, only one additional electron is required to fill in theoutermost shell of the hydrogen atom, so hydrogen can in some circumstances behave like a halogen, forming thenegative hydride ion. Binary compounds of hydrogen with the alkali metals and some transition metals have beenproduced in the laboratory, but these are only laboratory curiosities without much practical use. Under extremelyhigh pressures and low temperatures, such as those found at the cores of the planets Jupiter and Saturn, hydrogendoes become a metallic element, and it behaves like an alkali metal. (See metallic hydrogen.)The alkali metals have the lowest ionization potentials in their periods of the periodic table, because the removal of their single electrons from their outmost electron shells gives them the stable electron configuration of inert gases. Another way of stating this is that they all have a high electropositivity. The "second ionization potential" of all of

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Group I 47

the alkali metals is very high, since removing any electron from an atom having a noble gas configuration is difficultto do.

Series of alkali metals, stored in mineral oil("natrium" is sodium.)

All of the alkali metals are notable for their vigorous reactions withwater, and these reactions become increasingly vigorous when goingdown their column in the periodic table towards the heaviest alkalimetals, such as caesium. Their chemical reactions with water are asfollows:Alkali metal + water → Alkali metal hydroxide + hydrogen gasFor a typical example (M represents an alkali metal):

2 M (s) + 2 H2O (l) → 2 MOH (aq) + H2 (g)

TrendsLike in other columns of the periodic table, the members of the alkali metal family show patterns in their electronconfigurations, especially their outmost electron shells. This causes similar patterns in their chemical properties:

Z Element No. of electrons/shell

1 Hydrogen 1

3 Lithium 2, 1

11 Sodium 2, 8, 1

19 Potassium 2, 8, 8, 1

37 Rubidium 2, 8, 18, 8, 1

55 Caesium 2, 8, 18, 18, 8, 1

87 Francium 2, 8, 18, 32, 18, 8, 1

The alkali metals show a number of trends when moving down the group - for instance: decreasing electronegativity,increasing reactivity, and decreasing melting and boiling point. Their densities generally increase, with the notableexception that potassium is less dense than sodium, and the possible exception of francium being less dense thancaesium. (The highly radioactive element francium only exists in microscopic quantities.)

Alkali metal Standard atomic weight (u) Melting point (K) Boiling point (K) Density(g·cm−3)

Electronegativity (Pauling)

Lithium 6.941 453 1615 0.534 0.98

Sodium 22.990 370 1156 0.968 0.93

Potassium 39.098 336 1032 0.89 0.82

Rubidium 85.468 312 961 1.532 0.82

Caesium 132.905 301 944 1.93 0.79

Francium (223) 295 950 1.87 0.70

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Group I 48

CompoundsAlkali metals form a very wide range of amalgams.[1] They tend to form ionically bonded salts with mostelectronegative elements on the periodic table, like cesium fluoride and sodium chloride.

See also• alkaline earth metal• Lithium• Sodium• Potassium• Rubidium• Caesium• Francium

References[1] Deiseroth, H (1997). "Alkali metal amalgams, a group of unusual alloys". Progress in Solid State Chemistry 25: 73.

doi:10.1016/S0079-6786(97)81004-7.

• Campbell, Linda M., Aaron T. Fisk, Xianowa Wang, Gunter Kock, and Derek C. Muir (2005). "Evidence forBiomagnification of Rubidium in Freshwater and Marine Food Webs". Canadian Journal of Fisheries andAquatic Sciences 62: 1161–1167. doi:10.1139/f05-027.

• Chang, Cheng-Hung, and Tian Y. Tsong (2005). "Stochastic Resonance of Na, K-Ion Pumps on the Red CellMembrane". AIP Conference Proceedings: 18th International Conference on Noise and Fluctuations. 780.American Institute of Physics. pp. 587–590. doi:10.1063/1.2036821. ISBN 0-7354-0267-1.

• Joffe, Russell T., Stephen T. Sokolov and Anthony J. Levitt (2006). "Lithium and Triiodothyronine Augmentationof Antidepressants". Canadian Journal of Psychiatry 51 (12): 791–793. PMID 17168254.

• Bauer, Brent A., Robert Houlihan, Michael J. Ackerman, Katya Johnson, and Himeshkumar Vyas (2006)."Acquired Long QT Syndrome Secondary to Cesium Chloride Supplement". Journal of Alternative andComplementary Medicine 12 (10): 1011–1014. doi:10.1089/acm.2006.12.1011. PMID 17212573.

• Erermis, Serpil, Muge Tamar, Hatice Karasoy, Tezan Bildik, Eyup S. Ercan, and Ahmet Gockay (1997)."Double-Blind Randomised Trial of Modest Salt Restriction in Older People". Lancet 350: 850–854.doi:10.1016/S0140-6736(97)02264-2.

• Krachler, M, and E Rossipal (1999). "Trace Elements Transfer From Mother to the Newborn - Investigations onTriplets of Colostrum, Maternal and Umbilical Sera". European Journal of Clinical Nutrition 53 (6): 486–494.doi:10.1038/sj.ejcn.1600781. PMID 10403586.

• Stein, Benjamin P., Stephen G. Benka, Phillip F. Schewe, and Bertram Schwarzhild (1996). "Physics Update".Physics Today 49 (6): 9. doi:10.1063/1.2807642.

• "Group 1: The Alkali Metals" (http:/ / www. chemsoc. org/ Viselements/ pages/ data/ intro_groupi_data. html).Visual Elements. Royal Society of Chemistry. Retrieved 2009-12-08.

Page 52: Periodic Table

Group I 49

External links• Science aid:Alkali metals (http:/ / www. scienceaid. co. uk/ chemistry/ periodictable/ alkalimetals. html) A simple

look at alkali metals• Atomic and Physical Properties of the Group 1 Elements (http:/ / www. chemguide. co. uk/ inorganic/ group1/

properties. html) An in-depth look at alkali metals

Explanation of above periodic table slice:

Alkalimetals

Atomic numbers in blackare solids

Solid borders indicate primordial elements(older than the Earth)

Dashed borders indicate natural radioactive elements with noisotopes older than the Earth

Group II

Group → 2

↓ Period

2 4Be

3 12Mg

4 20Ca

5 38Sr

6 56Ba

7 88Ra

The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) (Group IIA) of the periodictable: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). This specificgroup in the periodic table owes its name to their oxides that simply give basic alkaline solutions. These oxides meltat such high temperature that they remain solids (“earths”) in fires. The alkaline earth metals provide a good exampleof group trends in properties in the periodic table, with well-characterized homologous behavior down the group.With the exception of Be and Mg, the metals have a distinguishable flame color, brick-red for Ca, magenta-red forSr, green for Ba and crimson red for Ra.Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

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Group II 50

Z Element No. of electrons/shell

4 Beryllium 2, 2

12 Magnesium 2, 8, 2

20 Calcium 2, 8, 8, 2

38 Strontium 2, 8, 18, 8, 2

56 Barium 2, 8, 18, 18, 8, 2

88 Radium 2, 8, 18, 32, 18, 8, 2

The alkaline earth metals are silver colored, soft metals, which react readily with halogens to form ionic salts, andwith water, though not as rapidly as the alkali metals, to form strong alkaline (basic) hydroxides. For example, wheresodium and potassium react with water at room temperature, magnesium reacts only with steam and calcium withhot water:

Mg + 2 H2O → Mg(OH)2 + H2Beryllium is an exception: It does not react with water or steam, and its halides are covalent.All the alkaline earth metals have two electrons in their valence shell, so the energetically preferred state ofachieving a filled electron shell is to lose two electrons to form doubly charged positive ions.The alkaline earth metals are named after their oxides, the alkaline earths, whose old-fashioned names were beryllia,magnesia, lime, strontia and baryta. These oxides are basic (alkaline) when combined with water. "Earth" is an oldterm applied by early chemists to nonmetallic substances that are insoluble in water and resistant toheating—properties shared by these oxides. The realization that these earths were not elements but compounds isattributed to the chemist Antoine Lavoisier. In his Traité Élémentaire de Chimie (Elements of Chemistry) of 1789 hecalled them salt-forming earth elements. Later, he suggested that the alkaline earths might be metal oxides, butadmitted that this was mere conjecture. In 1808, acting on Lavoisier's idea, Humphry Davy became the first to obtainsamples of the metals by electrolysis of their molten earths.

Biological occurrences

The alkaline earth metals.

• Beryllium's low aqueous solubilitymeans it is rarely available tobiological systems; it has no knownrole in living organisms, and whenencountered by them, is generallyhighly toxic.

• Magnesium and calcium are ubiquitousand essential to all known livingorganisms. They are involved in morethan one role, with, for example,Mg/Ca ion pumps playing a role insome cellular processes, magnesiumfunctioning as the active center insome enzymes, and calcium saltstaking a structural role (e.g. bones).

• Strontium and barium have a lower availability in the biosphere. Strontium plays an important role in marine aquatic life, especially hard corals. They use strontium to build their exoskeleton. These elements have some uses in medicine, for example "barium meals" in radio graphic imaging, whilst strontium compounds are employed in

Page 54: Periodic Table

Group II 51

some toothpastes.• Radium has a low availability and is highly radioactive, making it toxic to life.

Comparison of the physical properties and chemical properties betweenalkaline earth and alkali metalsJust like their names, they do not differ completely. The main difference is the electron configuration, which is ns2

for alkaline earth metals and ns1 for alkali metals. For the alkaline earth metals, there are two electrons that areavailable to form a metallic bond, and the nucleus contains an additional positive charge. Also, the elements of group2A (alkaline earth) have much higher melting points and boiling points compared to those of group 1A (alkalimetals). The alkali also have a softer and more lighweight figure whereas the alkaline earth metals are much harderand denser. The second valence electron is very important when it comes to comparing chemical properties of thealkaline earth and the alkali metals. The second valence electron is in the same “sublevel” as the first valenceelectron. Therefore, the Zeff is much greater. This means that the elements of the group 2A contain a smaller atomicradius and much higher ionization energy than the group 1A. Even though the group 2A contains much higherionization energy, they still form an ionic compound with 2+ cations. Beryllium, however, behaves differently. Thisis because in order to remove two electrons from this particular atom, it requires significantly more energy. It neverforms Be2+ and its bonds are polar covalent.

BerylliumAs mentioned earlier, Be is “special”; it behaves differently. If the Be2+ ion did exist, it would polarize electronclouds that are near it very strongly and would cause extensive orbital overlap, since Be has a high charge density.All compounds that include Be have a covalent bond. Even the compound BeF2 , which is the most ionic Becompound, has a low melting point and a low electrical conductivity when melted.

Important reactions and compoundsReactions:Note: E = elements that act as reducing agents1. The metals reduce halogens to form ionic halides: E(s) + X2 → EX2 (s) where X = F, Cl, Br or I2. The metals reduce O2 to form the oxides: 2E(s) + O2 → 2EO(s)3. The larger metals react with water to produce hydrogen gas: E(s) + 2H2O(l) → E2+

(aq) + 2OH-aq + H2 (g) where E =

Ca, Sr or BaCompounds1. Alkylmagnesium halides (RMgX where R = hydrocarbon group and X = halogen). They are used to synthetiseorganic compounds.Here’s an example: 3RMgCl + SnCl4 → 3MgCl2 + R3SnCl2. Magnesium oxide (MgO). It is used as a material to refract furnace brick and wire insulation (melting point of2852°C).3. Calcium carbonate (CaCO3). It is mainly used in the construction industry and for making limestone, marble,chalk, and coral.

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Group II 52

References• Group 2 - Alkaline Earth Metals [1], Royal Chemistry Society.• Group 1 Alkali Metals and Group 2 Alkaline Earth Metals [2], Doc Brown's Chemistry Clinic.• Science aid: Group 2 Metals [3] Study aid for teens• Maguire, Michael E. "Alkaline Earth Metals." Chemistry: Foundations and Applications. Ed. J. J. Lagowski. Vol.

1. New York: Macmillan Reference USA, 2004. 33-34. 4 vols. Gale Virtual Reference Library. Thomson Gale.• Silberberg, M.S., Chemistry: The molecular nature of Matter and Change (3e édition, McGraw-Hill 2009)• Petrucci R.H., Harwood W.S. et Herring F.G., General Chemistry (8e édition, Prentice-Hall 2002)

Explanation of above periodic table slice:

Alkaline earthmetals

Atomic numbers in blackindicate solids

Solid borders indicate primordialelements (older than the Earth)

Dashed borders indicate natural radioactive elementswith no isotopes older than the Earth

References[1] http:/ / www. chemsoc. org/ visElements/ pages/ data/ intro_groupii_data. html[2] http:/ / www. wpbschoolhouse. btinternet. co. uk/ page07/ sblock. htm[3] http:/ / scienceaid. co. uk/ chemistry/ fundamental/ group2. html

Group III

Period Group 3

421Sc

539Y

Group 3/ungrouped

*Lanthanides

**Actinides

6 *Lanthanides

Page 56: Periodic Table

Group III 53

57La

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

7 **Actinides

89Ac

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

The Group 3 elements are chemical elements comprising the third vertical column of the periodic table.IUPAC has not recommended a specific format for the periodic table, so different conventions are permitted and areoften used for group 3. The following d-block transition metals are always considered members of group 3:• scandium (Sc)• yttrium (Y)

The metals

Scandium Yttrium

When defining the remainder of group 3, four different conventions may be encountered:• Some tables [1] include lanthanum (La) and actinium (Ac), (the beginnings of the lanthanide and actinide series of

elements, respectively) as the remaining members of group 3. In their most commonly encountered tripositive ionforms, these elements do not possess any partially filled f orbitals, thus resulting in more d-block-like behavior.

• Some tables [2] include lutetium (Lu) and lawrencium (Lr) as the remaining members of group 3. These elements terminate the lanthanide and actinide series, respectively. Since the f-shell is nominally full in the ground state electron configuration for both of these metals, they behave most like d-block metals out of all the lanthanides

Page 57: Periodic Table

Group III 54

and actinides, and thus exhibit the most similarities in properties with Sc and Y. For Lr, this behavior is expected,but it has not been observed because sufficient quantities are not available. (See also Periodic table (wide) andPeriodic table (extended).)

Some tables [3] refer to all lanthanides and actinides by a marker in group 3. A third and fourth alternative aresuggested by this arrangement:• The third alternative is to regard all 30 lanthanide and actinide elements as included in group 3. Lanthanides, as

electropositive trivalent metals, all have a closely related chemistry, and all show many similarities to Sc and Y.• The fourth alternative is to include none of the lanthanides and actinides in group 3. The lanthanides possess

additional properties characteristic of their partially-filled f orbitals which are not common to Sc and Y.Furthermore, the actinides show a much wider variety of chemistry (for instance, in range of oxidation states)within their series than the lanthanides, and comparisons to Sc and Y are even less useful.

The term rare earth elements is often used for group 3 elements including the lanthanides but excluding theactinides.

OccurrenceScandium, yttrium, and the lanthanides (except promethium) tend to occur together in the Earth's crust, and arerelatively abundant compared with most d-block metals, but often harder to extract from their ores.

Biological chemistryGroup 3 elements are generally hard metals with low aqueous solubility, and have low availability to the biosphere.No group 3 has any documented biological role in living organisms. The radioactivity of the actinides generallymakes them highly toxic to living cells.

Notes

Explanation ofabove periodic

table slice:

Transitionmetals

Lanthanideseries

Actinideseries

Atomic numbersin black indicate

solids

Solid borders indicateprimordial elements

(older than the Earth)

Dashed bordersindicate natural

radioactive elements

Dotted bordersindicate synthetic

elements

References[1] Periodic table at Lanl.gov (http:/ / periodic. lanl. gov/ )[2] "WebElements Periodic Table of the Elements" (http:/ / www. webelements. com). Webelements.com. . Retrieved 2010-04-03.[3] "International Union of Pure and Applied Chemistry > Periodic Table of the Elements" (http:/ / www. iupac. org/ reports/ periodic_table/

index. html). Iupac.org. . Retrieved 2010-04-03.

Page 58: Periodic Table

Group IV 55

Group IV

Group → 4

↓ Period

4

22Ti

5

40Zr

6

72Hf

7 104Rf

Legend

Transition metal

Primordial element

Synthetic

The Group 4 elements are a group of chemical elements in the periodic table. In the modern IUPAC nomenclature,Group 4 of the periodic table contains titanium (Ti), zirconium (Zr), hafnium (Hf) and rutherfordium (Rf). Thisgroup lies in the d-block of the periodic table. The group itself has not acquired a trivial name; it belongs to thebroader grouping of the transition metals.The three Group 4 elements that occur naturally are titanium (Ti), zirconium (Zr) and hafnium (Hf). The first threemembers of the group share similar properties; all three are hard refractory metals under standard conditions.However the fourth element rutherfordium (Rf), has been synthesized in the laboratory, none of them have beenfound occurring in nature. All isotopes of rutherfordium are radioactive. So far, no experiments in a supercolliderwere conducted to synthesize the next member of the group Unpentquadium (Upq). As Upq is a late member ofperiod 8 element it is unlikely that this element will be synthesized in the near future.

Characteristics

ChemistryMost of the chemistry has been observed only for the first three members of the group, the chemistry ofrutherfordium is not very established and therefore the rest of the section deals only with titanium, zirconium, andhafnium. All the elements of the group are reactive metals with a high melting point (1668 °C, 1855 °C, 2233 °C).The reactivity is not always obvious due to the rapid formation of a stable oxide layer, which prevents furtherreactions. The oxides TiO2, ZrO2 and HfO2 are white solids with high melting points and unreactive against mostacids.[1]

Page 59: Periodic Table

Group IV 56

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac ** Rf Db Sg Bh Hs Mt Ds Rg Cn

* Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Group 4 in the periodic table

As tetravalent transition metals, all three elements form various inorganic compounds, generally in the oxidationstate of +4. For the first three metals, it has been shown that they are resistant to concentrated alkalis, but halogensreact with them to form tetrahalides. At higher temperatures, all three metals react with oxygen, nitrogen, carbon,boron, sulfur, and silicon. Because of the lanthanide contraction of the elements in the fifth period, zirconium andhafnium have nearly identical ionic radii. The ionic radius of Zr4+ is 79 picometers and that of Hf4+ is 78 pm.[1] [2]

This similarity results in nearly identical chemical behavior and in the formation of similar chemical compounds.[2]

The chemistry of hafnium is so similar to that of zirconium that a separation on chemical reactions was not possible,only the physical properties of the compounds differ. The melting points and boiling points of the compounds andthe solubility in solvents are the major differences in the chemistry of these twin elements.[1]

Physical

Properties of the Group 4 element

Name Titanium Zirconium Hafnium Rutherfordium

Melting point 1941 K (1668°C)

2130 K (1857°C)

2506 K (2233°C)

?

Boiling point 3560 K (3287°C)

4682 K (4409°C)

4876 K (4603°C)

?

Density 4.507 g·cm−3 6.511 g·cm−3 13.31  g·cm−3 ?

Appearance silver metallic silver white silver gray ?

Atomic radius 140 pm 155 pm 155 pm ?

Page 60: Periodic Table

Group IV 57

History

Crystal of the abundant mineral Ilmenite

While titanium and zirconium, as relatively abundant elements, werediscovered in the late 18th century, it took until 1923 for hafnium to beidentified. This was only partly due to hafnium's relative scarcity. Thechemical similarity between zirconium and hafnium made a separationdifficult and, without knowing what to look for, hafnium was leftundiscovered, although all samples of zirconium, and all of itscompounds, used by chemists for over two centuries containedsignificant amounts of hafnium.[3]

William Gregor, Franz Joseph Muller and Martin Heinrich Klaprothindependently discovered titanium between 1791 and 1795. Klaprothnamed it for the Titans of Greek mythology.[4] Klaproth also discovered zirconium in the mineral zircon in 1789 andnamed it after the already known Zirkonerde (zirconia). Hafnium had been predicted by Dmitri Mendeleev in 1869and Henry Moseley measured in 1914 the effective nuclear charge by X-ray spectroscopy to be 72, placing itbetween the already known elements lanthanum and tantalum. Dirk Coster and Georg von Hevesy were the first tosearch for the new element in zirconium ores.[5] Hafnium was discovered by the two in 1923 in Copenhagen,Denmark, validating the original 1869 prediction of Mendeleev.[6]

Rutherfordium was reportedly first detected in 1966 at the Joint Institute of Nuclear Research at Dubna (then in theSoviet Union). Researchers there bombarded 242Pu with accelerated 22Ne ions and separated the reaction productsby gradient thermochromatography after conversion to chlorides by interaction with ZrCl4.[7]

24294Pu + 22

10Ne → 264−x104Rf → 264−x

104RfCl4The next element after Rutherfordium is expected to be Unpentquadium (Upq). There are no plans to attempt tosynthesize the next element in the near future, since it is a late member of the Period 8 elements. Currently none ofthe period 8 elements have been discovered yet. It is also probable that, due to drip instabilities, only the lowerPeriod 8 elements are physically possible.

ProductionThe production of the metals itself is difficult due to their reactivity. The formation of oxides, nitrides and carbidesmust be avoided to yield workable metals, this is normally achieved by the Kroll process. The oxides (MO2) arereacted with coal and chlorine to form the chlorides (MCl4).The chlorides of the metals are than reacted withmagnesium yielding magnesium chloride and the metals.Further purification is done by a chemical transport reaction developed by Anton Eduard van Arkel and Jan Hendrikde Boer. In a closed vessel, the metal reacts with iodine at temperatures of above 500 °C forming metal(IV) iodide;at a tungsten filament of nearly 2000 °C the reverse reaction happens and the iodine and metal are set free. The metalforms a solid coating at the tungsten filament and the iodine can react with additional metal resulting in a steady turnover.[1] [8]

M + 2 I2 (low temp.) → MI4MI4 (high temp.) → M + 2 I2

Page 61: Periodic Table

Group IV 58

Occurrence

Heavy minerals (dark) in a quartz beach sand(Chennai, India).

If the abundance of elements in Earth's crust is compared for titanium,zirconium and hafnium, the abundance decreases with increase ofatomic mass. Titanium is the seventh most abundant metal in Earth'scrust and has an abundance of 6320 ppm, while zirconium has anabundance of 162 ppm and hafnium has only an abundance of 3ppm.[9]

All three stable elements occur in heavy mineral sands ore deposits,which are placer deposits formed, most usually in beach environments,by concentration due to the specific gravity of the mineral grains oferosion material from mafic and ultramafic rock. The titanium mineralsare mostly anatase and rutile, and zirconium occurs in the mineralzircon. Because of the chemical similarity, up to 5% of the zirconium in zircon is replaced by hafnium. The largestproducers of the group 4 elements are Australia, South Africa and Canada.[10] [11] [12] [13] [14]

ApplicationsTitanium metal and its alloys have a wide range of applications, where the corrosion resistance, the heat stability andthe low density (light weight) are of benefit. The foremost use of corrosion-resistant hafnium and zirconium has beenin nuclear reactors. Zirconium has a very low and hafnium has a high thermal neutron-capture cross-section.Therefore, zirconium (mostly as zircaloy) is used as cladding of fuel rods in nuclear reactors,[15] while hafnium isused as control rod for nuclear reactors, because each hafnium atom can absorb multiple neutrons.[16] [17]

Smaller amounts of hafnium[18] and zirconium are used in supper alloys to improve the properties of those alloys.[19]

Biological occurrencesThe group 4 elements are not known to be involved in the biological chemistry of any living systems.[20] They arehard refractory metals with low aqueous solubility and low availability to the biosphere. Titanium is one of the fewfirst row d-block transition metals with no known biological role. Rutherfordium's radioactivity would make it toxicto living cells.

PrecautionTitanium is non-toxic even in large doses and does not play any natural role inside the human body.[20] Zirconiumpowder can cause irritation, but only contact with the eyes requires medical attention.[21] OSHA recommends forzirconium are 5 mg/m3 time weighted average limit and a 10 mg/m3 short-term exposure limit.[22] Only limited dataexists on the toxicology of hafnium.[23]

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Group IV 59

References[1] Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils; (1985) (in German). Lehrbuch der Anorganischen Chemie (91-100 ed.). Walter de

Gruyter. pp. 1056–1057. ISBN 3110075113.[2] "Los Alamos National Laboratory – Hafnium" (http:/ / periodic. lanl. gov/ elements/ 72. html). . Retrieved 2008-09-10.[3] Barksdale, Jelks (1968). The Encyclopedia of the Chemical Elements. Skokie, Illinois: Reinhold Book Corporation. pp. 732–38 "Titanium".

LCCCN 68-29938.[4] Weeks, Mary Elvira (1932). "III. Some Eighteenth-Century Metals". Journal of Chemical Education: 1231–1243.[5] Urbain, M. G. (1922). "Sur les séries L du lutécium et de l'ytterbium et sur l'identification d'un celtium avec l'élément de nombre atomique 72

(The L series from lutetium to ytterbium and the identification of element 72 celtium" (http:/ / gallica. bnf. fr/ ark:/ 12148/ bpt6k3127j/ f1348.table) (in French). Comptes rendus 174: 1347–1349. . Retrieved 2008-10-30.

[6] Coster, D.; Hevesy, G. (1923-01-20). "On the Missing Element of Atomic Number 72". Nature 111: 79–79. doi:10.1038/111079a0.[7] Barber, R. C.; Greenwood, N. N.; Hrynkiewicz, A. Z.; Jeannin, Y. P.; Lefort, M.; Sakai, M.; Ulehla, I.; Wapstra, A. P.; Wilkinson, D. H.

(1993). "Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermiumelements" (http:/ / www. iupac. org/ publications/ pac/ 65/ 8/ 1757/ ). Pure and Applied Chemistry 65 (8): 1757–1814.doi:10.1351/pac199365081757. .

[8] van Arkel, A. E.; de Boer, J. H. (1925). "Darstellung von reinem Titanium-, Zirkonium-, Hafnium- und Thoriummetall (Production of puretitanium, zirconium, hafnium and Thorium metal)" (in German). Zeitschrift für anorganische und allgemeine Chemie 148 (1): 345–350.doi:10.1002/zaac.19251480133.

[9] "Abundance in Earth's Crust" (http:/ / www. webelements. com/ periodicity/ abundance_crust/ ). WebElements.com. . Retrieved 2007-04-14.[10] "Dubbo Zirconia Project Fact Sheet" (http:/ / www. alkane. com. au/ projects/ nsw/ dubbo/ DZP Summary June07. pdf) (PDF). Alkane

Resources Limited. June 2007. . Retrieved 2008-09-10.[11] "Zirconium and Hafnium" (http:/ / minerals. usgs. gov/ minerals/ pubs/ commodity/ zirconium/ mcs-2008-zirco. pdf) (PDF). Mineral

Commodity Summaries (US Geological Survey): 192–193. January 2008. . Retrieved 2008-02-24.[12] Callaghan, R. (2008-02-21). "Zirconium and Hafnium Statistics and Information" (http:/ / minerals. usgs. gov/ minerals/ pubs/ commodity/

zirconium/ ). US Geological Survey. . Retrieved 2008-02-24.[13] "Minerals Yearbook Commodity Summaries 2009: Titanium" (http:/ / minerals. usgs. gov/ minerals/ pubs/ commodity/ titanium/

myb1-2007-titan. pdf) (PDF). US Geological Survey. May 2009. . Retrieved 2008-02-24.[14] Gambogi, Joseph (January 2009). "Titanium and Titanium dioxide Statistics and Information" (http:/ / minerals. usgs. gov/ minerals/ pubs/

commodity/ titanium/ mcs-2009-titan. pdf). US Geological Survey. . Retrieved 2008-02-24.[15] Schemel, J. H. (1977). ASTM Manual on Zirconium and Hafnium (http:/ / books. google. com/ ?id=dI_LssydVeYC). ASTM International.

pp. 1–5. ISBN 9780803105058. .[16] Hedrick, James B.. "Hafnium" (http:/ / minerals. er. usgs. gov/ minerals/ pubs/ commodity/ zirconium/ 731798. pdf) (PDF). United States

Geological Survey. . Retrieved 2008-09-10.[17] Spink, Donald (1961). "Reactive Metals. Zirconium, Hafnium, and Titanium". Industrial and Engineering Chemistry 53 (2): 97–104.

doi:10.1021/ie50614a019.[18] Hebda, John (2001). "Niobium alloys and high Temperature Applications" (http:/ / www. cbmm. com. br/ portug/ sources/ techlib/

science_techno/ table_content/ sub_3/ images/ pdfs/ 016. pdf) (PDF). CBMM. . Retrieved 2008-09-04.[19] Donachie, Matthew J. (2002). Superalloys (http:/ / books. google. com/ ?id=vjCJ5pI1QpkC& pg=PA235). ASTM International.

pp. 235–236. ISBN 9780871707499. .[20] Emsley, John (2001). "Titanium". Nature's Building Blocks: An A-Z Guide to the Elements. Oxford, England, UK: Oxford University Press.

pp. 457–456. ISBN 0198503407.[21] "International Chemical Safety Cards" (http:/ / www. ilo. org/ legacy/ english/ protection/ safework/ cis/ products/ icsc/ dtasht/ _icsc14/

icsc1405. htm). International Labour Organization. October 2004. . Retrieved 2008-03-30.[22] "Zirconium Compounds" (http:/ / www. cdc. gov/ niosh/ pel88/ 7440-67. html). National Institute for Occupational Health and Safety.

2007-12-17. . Retrieved 2008-02-17.[23] "Occupational Safety & Health Administration: Hafnium" (http:/ / www. osha. gov/ SLTC/ healthguidelines/ hafnium/ index. html). U.S.

Department of Labor. . Retrieved 2008-09-10.

Page 63: Periodic Table

Group V 60

Group V

Group → 5

↓ Period

4

23V

5

41Nb

6

73Ta

7 105Db

A Group 5 element is one in the series of elements in group 5 (IUPAC style) in the periodic table, which consists ofvanadium (V), niobium (Nb), tantalum (Ta), and dubnium (Db).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells, though niobium curiously does not follow the trend:

Z Element No. of electrons/shell

23 vanadium 2, 8, 11, 2

41 niobium 2, 8, 18, 12, 1

73 tantalum 2, 8, 18, 32, 11, 2

105 dubnium 2, 8, 18, 32, 32, 11, 2

Dubnium can only be produced in the laboratory, and does not exist in nature.

Page 64: Periodic Table

Group V 61

HistoryThe discovery of all elements in the group led to controversies. The verification of those discoveries was difficultdue to similarity of vanadium and group 6 element chromium, the chemical similarity of niobium and tantalum andthe complicated setup which was necessary to produce a few atoms of dubnium.

Biological occurrencesOf the group 5 elements, only vanadium has been identified as playing a role in the biological chemistry of livingsystems: it is involved in some of the enzymes of higher organisms, and also, unusually, in the biochemistry of somemarine tunicates.

See also

Explanation of periodic tableslice on right:

Transitionmetals

atomic number inblack are solids

solid borders are older than the Earth(Primordial elements)

dotted borders are made artificially(Synthetic elements)

• Greenwood, N (2003). "Vanadium to dubnium: from confusion through clarity to complexity". Catalysis Today78: 5. doi:10.1016/S0920-5861(02)00318-8.

Group VI

Group → 6

↓ Period

4

24Cr

5

42Mo

6

74W

7 106Sg

Legend

Transition metal

Primordial element

Synthetic

Page 65: Periodic Table

Group VI 62

A Group 6 element is one in the series of elements in group 6 (IUPAC style) in the periodic table, which consists ofthe transition metals chromium (Cr), molybdenum (Mo), tungsten (W), and seaborgium (Sg).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

Z Element No. of electrons/shell

24 chromium 2, 8, 13, 1

42 molybdenum 2, 8, 18, 13, 1

74 tungsten 2, 8, 18, 32, 12, 2

106 seaborgium 2, 8, 18, 32, 32, 12, 2

"Group 6" is the new IUPAC name for this group; the old style name was "group VIA" in the old European system or"group VIB" in the old US system. Group 6 must not be confused with the group with the old-style group names ofeither VIB (European system) or VIA (US system); that group is now called group 16.

Biological occurrencesGroup 6 is notable in that it contains some of the only elements in periods 5 and 6 with a known role in thebiological chemistry of living organisms: molybdenum is common in enzymes of many organisms, and tungsten hasbeen identified in an analogous role in enzymes from some archaea, such as Pyrococcus furiosus. In contrast, andunusually for a first-row d-block transition metal, chromium appears to have few biological roles, although it isthought to form part of the glucose metabolism enzyme in some mammals.

See also

Explanation of right sideperiodic table slice:

Transitionmetals

atomic number inblack are solids

solid borders are older than the Earth(Primordial elements)

dotted borders are made artificially(Synthetic elements)

Page 66: Periodic Table

Group VII 63

Group VII

Group → 7

↓ Period

4 25Mn

5 43Tc

6 75Re

7 107Bh

A Group 7 element is one in the series of elements in group 7 (IUPAC style) in the periodic table, which consists ofthe transition metals manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

Z Element No. of electrons/shell

25 manganese 2, 8, 13, 2

43 technetium 2, 8, 18, 13, 2

75 rhenium 2, 8, 18, 32, 13, 2

107 bohrium 2, 8, 18, 32, 32, 13, 2

All of these elements are classed in Group 7 because their valence shells hold seven electrons. Technetium has nostable isotopes. Technetium and promethium are the only two such elements before lead, after which (with bismuthhaving an extremely long-lived isotope) no known element has a stable isotope.

OccurrenceTwo of the four members of the group 2, technetium and bohrium, are radioactive with short enough half life thatthey are not present in nature. Furthermore rhenium is a rare element which occurs only in traces in other mineral.These facts make manganese the only abundant element of the group. This is also shown in difference in the annualworld production. In 2007 11 million metric tons of manganese were mined while in the same year the worldproduction of rhenium was between 40 and 50 metric tons. They are also very reactive.

See also

Explanation of right sideperiodic table slice:

Transitionmetals

atomic number inblack are solids

solid borders are older thanthe Earth (Primordial

elements)

dotted borders are madeartificially (Synthetic

elements)

dashed borders have noisotopes older than the

earth

Page 67: Periodic Table

Group VIII 64

Group VIIIFor "Group VIII", the rightmost group on the Periodic Table, see noble gas.

Group → 4

↓ Period

4

26Fe

5

44Ru

6

76Os

7 108Hs

Legend

Transition metal

Primordial element

Synthetic

A Group 8 element is one in the series of elements in group 8 (IUPAC style) in the periodic table, which consists ofthe transition metals iron (Fe), ruthenium (Ru), osmium (Os) and hassium (Hs).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells though ruthenium curiously does not follow the trend:

Z Element No. of electrons/shell

26 iron 2, 8, 14, 2

44 ruthenium 2, 8, 18, 15, 1

76 osmium 2, 8, 18, 32, 14, 2

108 hassium 2, 8, 18, 32, 32, 14, 2

All of these elements are classed in Group 8 because their valence shells hold eight electrons. Hassium can only beproduced in the laboratory and has not been found in nature.

Page 68: Periodic Table

Group VIII 65

See also• Platinum group

Explanation of right sideperiodic table slice:

Transitionmetals

atomic number inblack are solids

solid borders are older than the Earth(Primordial elements)

dotted borders are made artificially(Synthetic elements)

Group IX

Group → 9

↓ Period

4 27Co

5 45Rh

6 77Ir

7 109Mt

In modern IUPAC nomenclature, Group 9 of the periodic table contains the elements cobalt (Co), rhodium (Rh),iridium (Ir), and meitnerium (Mt). These are all d-block transition metals. All known isotopes of Mt are radioactivewith short half-lives, and it is not known to occur in nature; only minute quantities have been synthesized inlaboratories.Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior, though rhodium curiously does not follow the pattern:

Z Element No. of electrons/shell

27 cobalt 2, 8, 15, 2

45 rhodium 2, 8, 18, 16, 1

77 iridium 2, 8, 18, 32, 15, 2

109 meitnerium 2, 8, 18, 32, 32, 15, 2

Applications• Alloys with other metals, primarily to add corrosion and wear resistance• Industrial Catalysts• Superalloys• Electrical Components

See also• Platinum group

Explanation of right sideperiodic table slice:

Transitionmetals

atomic number inblack are solids

solid borders are older than the Earth(Primordial elements)

dashed borders have no isotopesolder than the earth

Page 69: Periodic Table

Group X 66

Group X

Group → 10

↓ Period

4 28Ni

5 46Pd

6 78Pt

7 110Ds

A Group 10 element is one in the series of elements in group 10 (IUPAC style) in the periodic table, which consistsof the transition metals nickel (Ni), palladium (Pd), platinum (Pt), and darmstadtium (Ds).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells (though for this family it is particularly weak with palladium an exceptional case):

Z Element No. of electrons/shell

28 nickel 2, 8, 16, 2

46 palladium 2, 8, 18, 18

78 platinum 2, 8, 18, 32, 17, 1

110 darmstadtium 2, 8, 18, 32, 32, 17, 1

PropertiesGroup ten metals are white to light grey in color, and possess a high luster, a resistance to tarnish(oxidation) at STP,are highly ductile, and enter into oxidation states of +2 and +4, with +1 being seen in special conditions. Theexistence of a +3 state is debated, as the state could be an illusory state created by +2 and +4 states. Theory suggeststhat group 10 metals may produce a +6 oxidation state under precise conditions, but this remains to be provenconclusively in the laboratory.

ApplicationsThe group ten metals share several uses. These include:• Decorative purposes, in the form of jewelry and electroplating• Catalysts in a variety of chemical reactions• Metal Alloys• Electrical components, due to their predictable changes in electrical resistivity with regard to temperature.• Superconductors, as components in alloys with other metals.

Page 70: Periodic Table

Group X 67

See also• Platinum group

Explanation of right sideperiodic table slice:

Transitionmetals

atomic number inblack are solids

solid borders are older than the Earth(Primordial elements)

dashed borders have no isotopesolder than the earth

Group XI

Group → 11

↓ Period

4

29Cu

5

47Ag

6

79Au

7 111Rg

Legend

Transition metal

Primordial element

Synthetic

A Group 11 element is one in the series of elements in group 11 (IUPAC style) in the periodic table, consisting oftransition metals which are the traditional coinage metals of copper (Cu), silver (Ag), and gold (Au). Roentgenium(Rg) belongs to this group of elements based on its electronic configuration, but cannot be considered coinage metal(short lived transactinide with a 3.6 seconds half-life). The name "coinage metals" should not be used as analternative name for Group 11 elements, as various cultures have used other metals in coinage including aluminum,lead, nickel, stainless steel, and zinc). The term 'coinage metal' is not recognized by the International Union of Pureand Applied Chemistry (IUPAC) as a designator for group 11 elements.

Page 71: Periodic Table

Group XI 68

HistoryAll the elements of the group except Roentgenium have been known since prehistoric times, as all of them occur inmetallic form in nature and no extraction metallurgy has to be used to produce them.

CharacteristicsLike other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

Z Element No. of electrons/shell

29 copper 2, 8, 18, 1

47 silver 2, 8, 18, 18, 1

79 gold 2, 8, 18, 32, 18, 1

111 roentgenium 2, 8, 18, 32, 32, 18, 1

They are all relatively inert, corrosion-resistant metals. Copper and gold are colored.These elements have low electrical resistivity so they are used for wiring. Copper is the cheapest and most widelyused. Bond wires for integrated circuits are usually gold. Silver and silver plated copper wiring are found in somespecial applications.

ApplicationsThese metals, especially silver, have unusual properties that make them essential for industrial applications outsideof their monetary or decorative value. They are all excellent conductors of electricity. The most conductive of allmetals are silver, copper and gold in that order. Silver is also the most thermally conductive element, and the mostlight reflecting element. Silver also has the unusual property that the tarnish that forms on silver is still highlyelectrically conductive.Copper is used extensively in electrical wiring and circuitry. Gold contacts are sometimes found in precisionequipment for their ability to remain corrosion-free. Silver is used widely in mission-critical applications as electricalcontacts, and is also used in photography (because silver nitrate reverts to metal on exposure to light), agriculture,medicine, audiophile and scientific applications.Gold, silver, and copper are quite soft metals and so are easily damaged in daily use as coins. Precious metal mayalso be easily abraded and worn away through use. In their numismatic functions these metals must be alloyed withother metals to afford coins greater durability. The alloying with other metals makes the resulting coins harder, lesslikely to become deformed and more resistant to wear.Gold coins: Gold coins are typically produced as either 90% gold (e.g. with pre-1933 US coins), or 22 carat (92%)gold (e.g. current collectible coins and Krugerrands), with copper and silver making up the remaining weight in eachcase. Bullion gold coins are being produced with up to 99.999% gold (in the Canadian Gold Maple Leaf series).Silver coins: Silver coins are typically produced as either 90% silver - in the case of pre 1965 US minted coins(which were circulated in many countries), or sterling silver (92.5%) coins for pre-1967 British Commonwealth andother silver coinage, with copper making up the remaining weight in each case.Copper coins: Copper coins are often of quite high purity, around 97%, and are usually alloyed with small amountsof zinc and tin.Inflation has caused the face value of coins to fall below the hard currency value of the historically used metals. This had led to most modern coins being made of base metals - copper nickel (around 80:20, silver in color) is popular as are nickel-brass (copper (75), nickel (5) and zinc (20), gold in color), manganese-brass (copper, zinc, manganese,

Page 72: Periodic Table

Group XI 69

and nickel), bronze, or simple plated steel.

See also

Explanation of right sideperiodic table slice:

Transitionmetals

atomic numbers inblack are solids

solid borders are older than the Earth(Primordial elements)

dashed borders have no isotopesolder than the earth

Group XII

Group 11 12 13

Period4

29Cu

30Zn

31Ga

5 47Ag

48Cd

49In

6 79Au

80Hg

81Tl

7 112Cn

A group 12 element is one of the elements in group 12 (IUPAC style) in the periodic table, consisting of zinc (Zn),cadmium (Cd) and mercury (Hg).[1] [2] [3] The inclusion of copernicium (Cn) in group 12 is supported by recentexperiments on individual Cn atoms.[4]

Some properties of the elements

zinc cadmium mercury

Electronicconfiguration

[Ar]3d104s2 [Kr]4d105s2 [Xe]4f145d106s2

Metallic radius /pm 134 151 151

Ionic radius /pm (M2+) 74 95 102

Electronegativity 1.6 1.7 1.9

Melting point /°C 419.5 320.8 −38.9

Boiling point /°C 907 765 357

All elements in this group are metals. The similarity of the metallic radii of cadmium and mercury is a knock-oneffect of the lanthanide contraction. So, the trend in this group is unlike the trend in group 2, the alkaline earths,where metallic radius increases smoothly from top to bottom of the group. All three metals have relatively lowmelting and boiling points, which indicates that the metallic bond is relatively weak, with relatively little overlapbetween the valence band and the conduction band. Thus, zinc is close to the boundary between metallic andmetalloid elements which is usually placed between gallium and germanium, though gallium participates insemi-conductors such as gallium arsenide.Zinc is the most electropositive element in the group and zinc metal is a good reducing agent. The group oxidation state is +2 in which the ions have the rather stable d10 electronic configuration, with a full sub-shell. However, mercury can easily be reduced to the +1 oxidation state; usually, as in the ion Hg2

2+, two mercury(I) ions come together to form a metal-metal bond and a diamagnetic species. Cadmium can also form species such as [Cd2Cl6]4−

Page 73: Periodic Table

Group XII 70

in which the metal's oxidation state is +1. Just as with mercury, the formation of a metal-metal bond results in adiamagnetic compound in which there are no unpaired electrons which would otherwise make the species veryreactive. Zinc(I) is known only in the gas phase, in such compounds as linear Zn2Cl2, analogous to calomel.All three metal ions form many tetrahedral species, such as MCl4

2−. When a divalent ion of these elements forms atetrahedral complex, it obeys the octet rule. Both zinc and cadmium can also form octahedral complexes such as theaqua ions [M(H2O)6]2+ which are present in aqueous solutions of salts of these metals. Covalent character isachieved by using the 4d or 5d orbitals, respectively, forming sp3d2 hybrid orbitals. Mercury, however, rarelyexceeds a coordination number of four; when it does so the 5f orbitals must be involved. Coordination numbers of 2,3, 5, 7 and 8 are also known.The elements in group 12 are usually considered to be d-block elements, but not transition elements as the d-shell isfull. Some authors classify these elements as main-group elements because the valence electrons are in ns2 orbitals.Nevertheless zinc shares many characteristics with the neighbouring transition metal, copper. For instance, zinccomplexes merit inclusion in the Irving-Williams series as zinc forms many complexes with the same stoichiometryas complexes of copper(II), albeit with smaller stability constants. There is little similarity between cadmium andsilver as compounds of silver(II) are rare and those that do exist are very strong oxidizing agents. Likewise thecommon oxidation state for gold is +3, which precludes there being much common chemistry between mercury andgold, though there are similarities between mercury(I) and gold(I) such as the formation of linear dicyanocomplexes, [M(CN)2]−.

References[1] Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419[2] Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York:

Wiley-Interscience, ISBN 0-471-19957-5[3] Housecroft, C. E.; Sharpe, A. G. (2008). Inorganic Chemistry (3rd ed.). Prentice Hall. ISBN 978-0131755536.[4] Eichler, R; Aksenov, NV; Belozerov, AV; Bozhikov, GA; Chepigin, VI; Dmitriev, SN; Dressler, R; Gäggeler, HW et al. (2007). "Chemical

Characterization of Element 112". Nature 447 (7140): 72–75. doi:10.1038/nature05761. PMID 17476264.

Page 74: Periodic Table

Group XIII 71

Group XIII

Group → 13

↓ Period

2 5B

3 13Al

4 31Ga

5 49In

6 81Tl

The boron group is the series of elements in group 13 (IUPAC style) in the periodic table. The boron group consistsof boron (B), aluminium (Al), gallium (Ga), indium (In), thallium (Tl), and ununtrium (Uut).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

Z Element No. of electrons/shell

5 boron 2, 3

13 aluminium 2, 8, 3

31 gallium 2, 8, 18, 3

49 indium 2, 8, 18, 18, 3

81 thallium 2, 8, 18, 32, 18, 3

The group has previously also been referred to as the earth metals and the triels, from the Latin tri, three, stemmingfrom the naming convention of this group as Group IIIB. These elements are characterized by having three electronsin their outer energy levels (valence layers).Boron is considered a metalloid, and the rest are considered metals of the poor metals groups. Boron occurs sparselyprobably because of disruption of its nucleus by bombardment with subatomic particles produced from naturalradioactivity. Aluminium occurs widely on earth and in fact, it is the third most abundant element in the Earth's crust(7.4%).

Explanation of above periodic table slice:

Metalloids Poormetals

atomic number in black aresolids

solid borders are primordial elements (older thanthe Earth)

dotted borders are radioactive, syntheticelements

Page 75: Periodic Table

Group XIV 72

Group XIV

Group → 14

↓ Period

2 6C

3 14Si

4 32Ge

5 50Sn

6 82Pb

7 114Uuq

The carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead(Pb), and ununquadium (Uuq).In modern IUPAC notation, it is called Group 14. In the old IUPAC and CAS systems, it was called Group IVBand Group IVA, respectively.[1] In the field of semiconductor physics, it is still universally called Group IV. Thegroup was once also known as the tetrels (from Greek tetra, four), stemming from the Roman numeral IV in thegroup names, or (not coincidentally) from the fact that these elements have four valence electrons (see below).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

Z Element No. of electrons/shell

6 carbon 2, 4

14 silicon 2, 8, 4

32 germanium 2, 8, 18, 4

50 tin 2, 8, 18, 18, 4

82 lead 2, 8, 18, 32, 18, 4

114 ununquadium 2, 8, 18, 32, 32, 18, 4

Each of the elements in this group has 4 electrons in its outer energy level. The last orbital of all these elements is thep2 orbital. In most cases, the elements share their electrons. The tendency to lose electrons increases as the size of theatom increases, as it does with increasing atomic number. Carbon alone forms negative ions, in the form of carbide(C4−) ions. Silicon and germanium, both metalloids, each can form +4 ions. Tin and lead both are metals whileununquadium is a synthetic short-lived radioactive metal. Tin and lead are both capable of forming +2 ions.Except for germanium and ununquadium, all of these elements are familiar in daily life either as the pure element orin the form of compounds. However, except for silicon, none of these elements are particularly plentiful in theEarth’s crust. Carbon forms a very large variety of compounds, in both the plant and animal kingdoms. Silicon andsilicate minerals are fundamental components of the Earth’s crust; silica (silicon dioxide) is sand.Tin and lead, although with very low abundances in the crust, are nevertheless common in everyday life. They occur in highly concentrated mineral deposits, can be obtained easily in the metallic state from those minerals, and are

Page 76: Periodic Table

Group XIV 73

useful as metals and as alloys in many applications. Germanium, on the other hand, forms few characteristicminerals and is most commonly found only in small concentrations in association with the mineral zinc blende andin coals. Although germanium is indeed one of the rarer elements, it assumed importance upon recognition of itsproperties as a semiconductor.

HistoryCarbon, tin, and lead, are a few of the elements well known in the ancient world - together with sulfur, iron, copper,mercury, silver, and gold.Carbon as an element was discovered by the first human to handle charcoal from his fire. Modern carbon chemistrydates from the development of coals, petroleum, and natural gas as fuels and from the elucidation of syntheticorganic chemistry, both substantially developed since the 1800s.Amorphous elemental silicon was first obtained pure in 1824 by the Swedish chemist Jöns Jacob Berzelius; impuresilicon had already been obtained in 1811. Crystalline elemental silicon was not prepared until 1854, when it wasobtained as a product of electrolysis. In the form of rock crystal, however, silicon was familiar to the predynasticEgyptians, who used it for beads and small vases; to the early Chinese; and probably to many others of the ancients.The manufacture of glass containing silica was carried out both by the Egyptians — at least as early as 1500 BCE —and by the Phoenicians. Certainly, many of the naturally occurring compounds called silicates were used in variouskinds of mortar for construction of dwellings by the earliest people.Germanium is one of three elements the existence of which was predicted in 1871 by the Russian chemist DmitriMendeleev when he first devised his periodic table. Not until 1886, however, was germanium identified as one of theelements in a newly found mineral.The origins of tin seem to be lost in history. It appears that bronzes, which are alloys of copper and tin, were used byprehistoric man some time before the pure metal was isolated. Bronzes were common in early Mesopotamia, theIndus Valley, Egypt, Crete, Israel, and Peru. Much of the tin used by the early Mediterranean peoples apparentlycame from the Scilly Isles and Cornwall in the British Isles,[2] where mining of the metal dates from about 300–200BCE. Tin mines were operating in both the Inca and Aztec areas of South and Central America before the Spanishconquest.Lead is mentioned often in early Biblical accounts. The Babylonians used the metal as plates on which to recordinscriptions. The Romans used it for tablets, water pipes, coins, and even cooking utensils; indeed, as a result of thelast use, lead poisoning was recognized in the time of Augustus Caesar. The compound known as white lead wasapparently prepared as a decorative pigment at least as early as 200 BCE. Modern developments date to theexploitation in the late 1700s of deposits in the Missouri–Kansas–Oklahoma area in the United States.

Explanation of above periodic table slice:

Nonmetals Metalloids Poormetals

atomic number in blackare solids

solid borders are primordial elements(older than the Earth)

dotted borders are radioactive,synthetic elements

References[1] Fluck, E. New notations in the periodic table. Pure & App. Chem. 1988, 60, 431-436. (http:/ / www. iupac. org/ publications/ pac/ 1988/ pdf/

6003x0431. pdf)[2] Online Encyclopaedia Britannica, Tin (http:/ / www. britannica. com/ EBchecked/ topic/ 596431/ tin)

Page 77: Periodic Table

Group XV 74

Group XV

Group → 15

↓ Period

2 7N

3 15P

4 33As

5 51Sb

6 83Bi

7 115Uup

The nitrogen group is a periodic table group consisting of nitrogen (N), phosphorus (P), arsenic (As), antimony(Sb), bismuth (Bi) and ununpentium (Uup) (unconfirmed).In modern IUPAC notation, it is called Group 15. In the old IUPAC and CAS systems, it was called Group VB andGroup VA, respectively (pronounced "group five B" and "group five A", because "V" is a Roman numeral).[1] In thefield of semiconductor physics, it is still universally called Group V.[2] It is also collectively named thepnictogens.[3] The "five" ("V") in the historical names comes from the fact that these elements have five valenceelectrons (see below).Like other groups, the members of this family show patterns in its electron configuration, especially the outermostshells resulting in trends in chemical behavior:

Z Element No. of electrons/shell

7 nitrogen 2, 5

15 phosphorus 2, 8, 5

33 arsenic 2, 8, 18, 5

51 antimony 2, 8, 18, 18, 5

83 bismuth 2, 8, 18, 32, 18, 5

115 ununpentium 2, 8, 18, 32, 32, 18, 5

This group has the defining characteristic that all the component elements have 5 electrons in their outermost shell,that is 2 electrons in the s subshell and 3 unpaired electrons in the p subshell. They are therefore 3 electrons short offilling their outermost electron shell in their non-ionized state. The most important element of this group is nitrogen(chemical symbol N), which in its diatomic form is the principal component of air.Binary compounds of the group can be referred to collectively as pnictides. The spelling derives from the Greekπνίγειν (pnigein), to choke or stifle, which is a property of nitrogen; they are also mnemonic for the two mostcommon members, P and N. The name pentels (from the Latin penta, five) was also used for this group at one time,stemming from the earlier group naming convention (Group VB).

Page 78: Periodic Table

Group XV 75

A collection of nitrogen-group chemical elementsamples.

These elements are also noted for their stability in compounds due totheir tendency for forming double and triple covalent bonds. This is theproperty of these elements which leads to their potential toxicity, mostevident in phosphorus, arsenic and antimony. When these substancesreact with various chemicals of the body, they create strong freeradicals not easily processed by the liver, where they accumulate.Paradoxically it is this strong bonding which causes nitrogen andbismuth's reduced toxicity (when in molecules), as these form strongbonds with other atoms which are difficult to split, creating veryunreactive molecules. For example N2, the diatomic form of nitrogen,is used for inert atmosphere in situations where argon or another noblegas would be prohibitively expensive.

The nitrogen group consists of two non-metals, two metalloids, one metal, and one synthetic (presumably metallic)element. All the elements in the group are a solid at room temperature except for Nitrogen which is a gas at roomtemperature. Nitrogen and bismuth, despite both being part of the nitrogen group, are very different in their physicalproperties. For example, at STP nitrogen is a transparent nonmetallic gas, while bismuth is a brittle pinkish metallicsolid.

See also• oxypnictide includes superconductors discovered in 2008• ferropnictide includes oxypnictide superconductors.

Notes[1] Fluck, E. New notations in the periodic table. Pure & App. Chem. 1988, 60, 431-436. (http:/ / www. iupac. org/ publications/ pac/ 1988/ pdf/

6003x0431. pdf)[2] For example, a 2005 book (http:/ / books. google. com/ books?id=J6W5n5Z1EQIC) is titled Properties of group-IV, III-V and II-VI

semiconductors.[3] Edited by N G Connelly and T Damhus (with R M Hartshorn and A T Hutton), ed (2005). Nomenclature of Inorganic Chemistry: IUPAC

Recommendations 2005 section IR-3.5 (http:/ / www. iupac. org/ publications/ books/ rbook/ Red_Book_2005. pdf). ISBN 0-85404-438-8. .

Explanation of above periodic table slice:

Nonmetals Metalloids Poormetals

atomic number inred are gases

atomic number inblack are solids

solid borders are primordialelements (older than the Earth)

dotted borders are radioactive,synthetic elements

Page 79: Periodic Table

Group XVI 76

Group XVI

Group → 16

↓ Period

2 8O

3 16S

4 34Se

5 52Te

6 84Po

7 116Uuh

The chalcogens (pronounced /ˈkælkədʒɨn/) are the chemical elements in group 16 (old-style: VIB or VIA) of theperiodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulfur (S),selenium (Se), tellurium (Te), the radioactive element polonium (Po), and the synthetic element ununhexium (Uuh).Although all group 16 elements of the periodic table, including oxygen are defined as chalcogens, oxygen and oxidesare usually distinguished from chalcogens and chalcogenides. The term chalcogenide is more commonly reservedfor sulfides, selenides, and tellurides, rather than for oxides. Oxides are usually not indicated as chalcogenides.[1] [2]

[3] [4] Binary compounds of the chalcogens are called chalcogenides (rather than chalcides, which breaks the patternof halogen/halide and pnictogen/pnictide).

PropertiesMembers of this group show similar patterns in their electron configuration, especially the outermost shells, resultingin similar trends in chemical behavior:

Z Element No. of electrons/shell

8 oxygen 2, 6

16 sulfur 2, 8, 6

34 selenium 2, 8, 18, 6

52 tellurium 2, 8, 18, 18, 6

84 polonium 2, 8, 18, 32, 18, 6

116 ununhexium 2, 8, 18, 32, 32, 18, 6

Oxygen and sulfur are nonmetals, and selenium, tellurium, and polonium are metalloid semiconductors (that means,their electrical properties are between those of a metal and an insulator). Nevertheless, tellurium, as well as selenium,is often referred to as a metal when in elemental form.Metal chalcogenides are common as minerals. For example, pyrite (FeS2) is an iron ore. The rare mineral calaveriteis the ditelluride AuTe2.

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Group XVI 77

The formal oxidation number of the most common chalcogen copounds is −2. Other values, such as −1 in pyrite, canbe attained. The highest formal oxidation number +6 is found in sulfates, selenates and tellurates, such as in sulfuricacid or sodium selenate (Na2SeO4).

Explanation of above periodic table slice:

Nonmetals Metalloids Poormetals

Atomicnumbers in red

are gases

Atomicnumbers in

black are solids

Solid borders indicateprimordial elements

(older than the Earth)

Dashed bordersindicate radioactive

natural elements

Dotted bordersindicate radioactivesynthetic elements

EtymologyThe name chalcogen comes from the Greek words χαλκος (chalkos, literally "copper"), and γενεσ (genes, born)[5] .Thus the chalcogens give birth to, produce copper. It was first used around 1930 by Wilhelm Biltz's group at theUniversity of Hanover, where it was proposed by a man named Werner Fischer.[6] Although the literal meanings ofthe Greek words imply that chalcogen means "copper-former", this is misleading because the chalcogens havenothing to do with copper in particular. "Ore-former" has been suggested as a better translation,[7] both because thevast majority of metal ores are chalcogenides, and because the word χαλκος in ancient Greek was associated withmetals and metal-bearing rock in general (because copper, and its alloy bronze, was one of the first metals to be usedby humans).

See also• Gold chalcogenides

References[1] A Second Note on the Term "Chalcogen" (http:/ / jchemed. chem. wisc. edu/ Journal/ Issues/ 2001/ Oct/ abs1333_1. html)[2] Francesco Devillanova (Editor) Handbook of Chalcogen Chemistry - New Perspectives in Sulfur, Selenium and Tellurium (http:/ / books.

google. com/ books?id=IvGnUAaSqOsC& pg=PT24) Royal Society of Chemistry, 2007; ISBN 0854043667, 9780854043668[3] IUPAC goldbook amides (http:/ / goldbook. iupac. org/ A00266. html). Chalcogen replacement analogues (of amides) are called thio-, seleno-

and telluro-amides.[4] Ohno Takahisa Passivation of GaAs(001) surfaces by chalcogen atoms (S, Se and Te) (http:/ / www. sciencedirect. com/

science?_ob=ArticleURL& _udi=B6TVX-46T3HTC-JF& _user=10& _rdoc=1& _fmt=& _orig=search& _sort=d& _docanchor=& view=c&_acct=C000050221& _version=1& _urlVersion=0& _userid=10& md5=aae920d4ee8b01faf1150483b04710a8) Surface Science; Volume 255,Issue 3, 2 September 1991, Pages 229-236; doi:10.1016/0039-6028(91)90679-M

[5] Online Etymology Dictionary -gen (http:/ / www. etymonline. com/ index. php?term=-gen)[6] Werner Fischer (2001). "A Second Note on the Term "Chalcogen"". Journal of Chemical Education 78 (10): 1333.

doi:10.1021/ed078p1333.1.[7] William B. Jensen (1997). Journal of Chemical Education 74 (9): 1063. doi:10.1021/ed074p1063.

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Group XVII 78

Group XVII

Group → 17

↓ Period

2 9F

3 17Cl

4 35Br

5 53I

6 85At

7 117Uus

Legend

Halogen

Gas

Liquid

Primordial element

From decay

Synthetic

The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style (formerly: VII,VIIA) of the periodic table, comprising fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Theartificially created element 117, provisionally referred to by the systematic name ununseptium, may also be ahalogen.The group of halogens is the only periodic table group which contains elements in all three familiar states of matterat standard temperature and pressure.

AbundanceOwing to their high reactivity, the halogens are found in the environment only in compounds or as ions. Halide ionsand oxoanions such as iodate (IO3

−) can be found in many minerals and in seawater. Halogenated organiccompounds can also be found as natural products in living organisms. In their elemental forms, the halogens exist asdiatomic molecules, but these only have a fleeting existence in nature and are much more common in the laboratoryand in industry. At room temperature and pressure, fluorine and chlorine are gases, bromine is a liquid and iodineand astatine are solids; Group 17 is therefore the only periodic table group exhibiting all three states of matter atroom temperature.

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Group XVII 79

EtymologyThe Swedish chemist Baron Jöns Jakob Berzelius coined the term "halogen" – ἅλς (háls), "salt" or "sea", and γεν-(gen-), from γίγνομαι (gígnomai), "come to be" – for an element that produces a salt when it forms a compoundwith a metal.[1]

Properties

Fluorine, (F); chlorine, (Cl); bromine, (Br); iodine, (I) at room temperature. The firsttwo are gaseous, the third is liquid and the fourth is solid.

Like other groups, the candidates of thisfamily show patterns in its electronconfiguration, especially the outermostshells resulting in trends in chemicalbehavior:

Z Element No. of electrons/shell

9 fluorine 2, 7

17 chlorine 2, 8, 7

35 bromine 2, 8, 18, 7

53 iodine 2, 8, 18, 18, 7

85 astatine 2, 8, 18, 32, 18, 7

117 ununseptium 2, 8, 18, 32, 32, 18, 7

The halogens show a series of trends when moving down the group—for instance, decreasing electronegativity andreactivity, and increasing melting and boiling point.

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Group XVII 80

Halogen Standard Atomic Weight (u) Melting Point (K) Boiling Point (K) Electronegativity (Pauling)

Fluorine 18.998 53.53 85.03 3.98

Chlorine 35.453 171.60 239.11 3.16

Bromine 79.904 265.80 332.00 2.96

Iodine 126.904 386.85 457.40 2.66

Astatine (210) 575 610 (?) 2.20

Diatomic halogen molecules

halogen molecule structure model d(X−X) /pm

(gas phase)

d(X−X) / pm(solid phase)

fluorine F2 143 149

chlorine Cl2 199 198

bromine Br2 228 227

iodine I2 266 272

The elements become less reactive and have higher melting points as the atomic number increases.

Chemistry

ReactivityHalogens are highly reactive, and as such can be harmful or lethal to biological organisms in sufficient quantities.This high reactivity is due to the atoms being highly electronegative due to their high effective nuclear charge. Theycan gain an electron by reacting with atoms of other elements. Fluorine is one of the most reactive elements inexistence, attacking otherwise inert materials such as glass, and forming compounds with the heavier noble gases. Itis a corrosive and highly toxic gas. The reactivity of fluorine is such that if used or stored in laboratory glassware, itcan react with glass in the presence of small amounts of water to form silicon tetrafluoride (SiF4). Thus fluorine mustbe handled with substances such as Teflon (which is itself an organofluorine compound), extremely dry glass, ormetals such as copper or steel which form a protective layer of fluoride on their surface.The high reactivity of fluorine means that once it does react with something, it bonds with it so strongly that theresulting molecule is very inert and non-reactive to anything else. For example, Teflon is fluorine bonded withcarbon.Both chlorine and bromine are used as disinfectants for drinking water, swimming pools, fresh wounds, spas, dishes,and surfaces. They kill bacteria and other potentially harmful microorganisms through a process known assterilization. Their reactivity is also put to use in bleaching. Sodium hypochlorite, which is produced from chlorine,is the active ingredient of most fabric bleaches and chlorine-derived bleaches are used in the production of somepaper products.

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Group XVII 81

Hydrogen halidesThe halogens all form binary compounds with hydrogen known as the hydrogen halides (HF, HCl, HBr, HI, andHAt), a series of particularly strong acids. When in aqueous solution, the hydrogen halides are known as hydrohalicacids. HAt, or "hydroastatic acid", should also qualify, but it is not typically included in discussions of hydrohalicacid due to astatine's extreme instability toward alpha decay.

Interhalogen compoundsThe halogens react with each other to form interhalogen compounds. Diatomic interhalogen compounds such as BrF,ICl, and ClF bear resemblance to the pure halogens in some respects. The properties and behaviour of a diatomicinterhalogen compound tend to be intermediate between those of its parent halogens. Some properties, however, arefound in neither parent halogen. For example, Cl2 and I2 are soluble in CCl4, but ICl is not since it is a polarmolecule due to the relatively large electronegativity difference between I and Cl.

Organohalogen compoundsMany synthetic organic compounds such as plastic polymers, and a few natural ones, contain halogen atoms; theseare known as halogenated compounds or organic halides. Chlorine is by far the most abundant of the halogens, andthe only one needed in relatively large amounts (as chloride ions) by humans. For example, chloride ions play a keyrole in brain function by mediating the action of the inhibitory transmitter GABA and are also used by the body toproduce stomach acid. Iodine is needed in trace amounts for the production of thyroid hormones such as thyroxine.On the other hand, neither fluorine nor bromine are believed to be essential for humans.

Polyhalogenated compoundsPolyhalogenated compounds are industrially created compounds substituted with multiple halogens. Many of themare very toxic and bioaccumulate in humans, and have a very wide application range. They include the muchmaligned PCB's, PBDE's, and PFC's as well as numerous other compounds.

Drug discoveryIn drug discovery, the incorporation of halogen atoms into a lead drug candidate results in analogues that are usuallymore lipophilic and less water soluble.[2] Consequently, halogen atoms are used to improve penetration through lipidmembranes and tissues. Consequently, there is a tendency for some halogenated drugs to accumulate in adiposetissue.The chemical reactivity of halogen atoms depends on both their point of attachment to the lead and the nature of thehalogen. Aromatic halogen groups are far less reactive than aliphatic halogen groups, which can exhibit considerablechemical reactivity. For aliphatic carbon-halogen bonds the C-F bond is the strongest and usually less chemicallyreactive than aliphatic C-H bonds. The other aliphatic-halogen bonds are weaker, their reactivity increasing down theperiodic table. They are usually more chemically reactive than aliphatic C-H bonds. Consequently, the most commonhalogen substitutions are the less reactive aromatic fluorine and chlorine groups.

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Group XVII 82

Reactivity with waterFluorine reacts vigorously with water to produce oxygen (O2) and hydrogen fluoride (HF):[3]

2 F2(g) + 2 H2O(l) → O2(g) + 4 HF(aq)Chlorine has minimal solubility of 0.7g Cl2 per kg of water at ambient temperature (21oC).[4] Dissolved chlorinereacts to form hydrochloric acid (HCl) and hypochlorous acid, a solution that can be used as a disinfectant or bleach:

Cl2(g) + H2O(l) → HCl(aq) + HClO(aq)Bromine has a solubility of 3.41 g per 100 g of water,[5] but it slowly reacts to form hydrogen bromide (HBr) andhypobromous acid (HBrO):

Br2(g) + H2O(l) → HBr(aq) + HBrO(aq)Iodine, however, is minimally soluble in water (0.03 g/100 g water @ 20 °C) and does not react with it.[6] However,iodine will form an aqueous solution in the presence of iodide ion, such as by addition of potassium iodide (KI),because the triiodide ion is formed.

See also• Pseudohalogen• Halogen bond• Halogen lamp

Further reading• N. N. Greenwood, A. Earnshaw, Chemistry of the Elements [7], 2nd ed., Butterworth-Heinemann, Oxford, UK,

1997.

Explanation of above periodic table slice:

Halogens Atomic numbers in red are gases Atomic numbers in green areliquids

Atomic numbers in black aresolids

Solid borders indicate primordialelements (older than the Earth)

Dashed borders indicateradioactive natural elements

Dotted borders indicate radioactivesynthetic elements

No borders indicatesundiscovered elements

References[1] Online Etymology Dictionary halogen (http:/ / www. etymonline. com/ index. php?search=halogen).[2] G. Thomas, Medicinal Chemistry an Introduction, John Wiley & Sons, West Sussex, UK, 2000.[3] The Oxidising Ability of the Group 7 Elements (http:/ / www. chemguide. co. uk/ inorganic/ group7/ halogensasoas. html)[4] Solubility of chlorine in water (http:/ / www. resistoflex. com/ chlorine_graphs. htm#9)[5] Properties of bromine (http:/ / www. bromaid. org/ hand_chap1. htm)[6] Iodine MSDS (http:/ / www. jtbaker. com/ msds/ englishhtml/ I2680. htm)[7] http:/ / www. knovel. com/ knovel2/ Toc. jsp?BookID=402

Page 86: Periodic Table

Group XVIII 83

Group XVIII

Group → 18

↓ Period

1 2He

2 10Ne

3 18Ar

4 36Kr

5 54Xe

6 86Rn

7 118Uuo

Legend

Noble gas

Gas

Primordial element

From decay

Synthetic

A group 18 element is any chemical element from the last column of the standard periodic table.For the first six periods, the group 18 elements are exactly the noble gases. However, the seventh member of group18 (the synthetic element ununoctium) is probably not a noble gas.Group 18 was previously called 'group 8A' or 'group 0'.

PropertiesAccording to the classical shell model for electrons, the group 18 elements have a fully filled outer shell, renderingthem inert to most chemical reactions. This holds true for the first six elements of this group (though they tend tobecome slightly less inert with increasing periods). For the seventh period group 18 element (ununoctium), this"nobility" is predicted to break down due to relativistic effects.[1]

See alsoNoble gas

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Group XVIII 84

References[1] Clinton S. Nash (2005). "Atomic and Molecular Properties of Elements 112, 114, and 118". J. Phys. Chem. A 109 (15): 3493–3500.

doi:10.1021/jp050736o. PMID 16833687.

Page 88: Periodic Table

85

Periods

PeriodIn the periodic table of the elements, elements are arranged in a series of rows (or periods) so that those with similarproperties appear in vertical columns. Elements of the same period have the same number of electron shells; witheach group across a period, the elements have one more proton and electron and become less metallic. Thisarrangement reflects the periodic recurrence of similar properties as the atomic number increases. For example, thealkaline metals lie in one group (group 1) and share similar properties, such as high reactivity and the tendency tolose one electron to arrive at a noble-gas electronic configuration.Modern quantum mechanics explains these periodic trends in properties in terms of electron shells. As atomicnumber increases, shells fill with electrons in approximately the order shown below. The filling of each shellcorresponds to a row in the table.

1s2s 2p3s 3p 3d4s 4p 4d 4f5s 5p 5d 5f6s 6p 6d7s 7p8s

In the s-block and p-block of the periodic table, elements within the same period generally do not exhibit trends andsimilarities in properties (vertical trends down groups are more significant). However in the d-block, trends acrossperiods become significant, and in the f-block elements show a high degree of similarity across periods (particularlythe lanthanides).

PeriodsSeven periods of elements occur naturally on Earth. For period 8, which includes elements which may besynthesized after 2010, see the extended periodic table.A group in chemistry means a family of objects with similarities like different families.

Chemical elements in the first period

Group 1/17 2/18

#Name

1H

2He

The first period contains fewer elements than any other, with only two, hydrogen and helium. They therefore do notfollow the octet rule. Chemically, helium behaves as a noble gas, and thus is taken to be part of the group 18elements. However, in terms of its nuclear structure it belongs to the s block, and is therefore sometimes classified asa group 2 element, or simultaneously both 2 and 18. Hydrogen readily loses and gains an electron, and so behaveschemically as both a group 1 and a group 17 element.

Page 89: Periodic Table

Period 86

• Hydrogen (H) is the most abundant of the chemical elements, constituting roughly 75% of the universe'selemental mass.[1] Ionized hydrogen is just a proton. Stars in the main sequence are mainly composed ofhydrogen in its plasma state. Elemental hydrogen is relatively rare on Earth, and is industrially produced fromhydrocarbons such as methane. Hydrogen can form compounds with most elements and is present in water andmost organic compounds.[2]

• Helium (He) exists only as a gas except in extreme conditions.[3] It is the second lightest element and is thesecond most abundant in the universe.[4] Most helium was formed during the Big Bang, but new helium is createdthrough nuclear fusion of hydrogen in stars.[5] On Earth, helium is relatively rare, only occurring as a byproductof the natural decay of some radioactive elements.[6] Such 'radiogenic' helium is trapped within natural gas inconcentrations of up to seven percent by volume.[7]

Chemical elements in the second period

Group 1 2 13 14 15 16 17 18

#Name

3Li

4Be

5B

6C

7N

8O

9F

10Ne

Period 2 elements involve the 2s and 2p orbitals. They include the biologically most essential elements besideshydrogen: carbon, nitrogen, and oxygen.• Lithium is the lightest metal and the least dense solid element.[8] In its non-ionized state it is one of the most

reactive elements, and so is only ever found naturally in compounds. It is the heaviest primordial element forgedin large quantities during the Big Bang.

• Beryllium has one of the highest melting points of all the light metals. Small amounts of beryllium weresynthesised during the Big Bang, although most of it decayed or reacted further within stars to create largernucleii, like carbon, nitrogen or oxygen. Beryllium is classified by the International Agency for Research onCancer as Group 1 carcinogens.[9] Between 1% and 15% of people are sensitive to beryllium and may develop aninflammatory reaction in their respiratory system and skin, called chronic beryllium disease.[10]

• Boron (B) does not occur naturally as a free element, but in compounds such as borates. It is an essential plantmicronutrient, required for cell wall strength and development, cell division, seed and fruit development, sugartransport and hormone development,[11] [12] though high levels are toxic.

• Carbon (C) is the fourth most abundant element in the universe by mass after hydrogen, helium and oxygen[13]

and is the second most abundant element in the human body by mass after oxygen,[14] the third most abundant bynumber of atoms.[15] There are an almost infinite number of compounds that contain carbon due to carbon'sability to form long stable chains of C—C bonds.[16] [17] All organic compounds, those essential for life, containat least one atom of carbon;[16] [17] combined with hydrogen, oxygen, nitrogen, sulfur, and phosphorus, carbon isthe basis of every important biological compound.[17]

• Nitrogen (N) is found mainly as mostly inert diatomic gas, N2, which makes up 78% of the earth's atmosphere. Itis an essential component of proteins and therefore of life.

• Oxygen (O) comprising 21% of the atmosphere and is required for respiration by all (or nearly all) animals, aswell as being the principal component of water. Oxygen is the third most abundant element in the universe, andoxygen compounds dominate the earth's crust.

• Fluorine (F) is the most reactive element in its non-ionized state, and so is never found that way in nature.• Neon is a noble gas used in neon lights.

Page 90: Periodic Table

Period 87

Chemical elements in the third period

Group 1 2 13 14 15 16 17 18

#Name

11Na

12Mg

13Al

14Si

15P

16S

17Cl

18Ar

All period three elements occur in nature and have at least one stable isotope. All but the noble gas argon are allessential to basic geology and biology.• Sodium (symbol Na) is an alkali metal. It is present in Earth's oceans in large quantities in the form of sodium

chloride (table salt).• Magnesium (symbol Mg) is an alkaline earth metal. Magnesium ions are found in chlorophyll.• Aluminium (symbol Al) is a poor metal. It is the most abundant metal in the Earth's crust.• Silicon (symbol Si) is a metalloid. It is a semiconductor, making it the principal component in many integrated

circuits. Silicon dioxide is the principal constituent of sand.• Phosphorus (symbol P) is a nonmetal essential to DNA. It is highly reactive, and as such is never found in nature

as a free element.• Sulfur (symbol S) is a nonmetal. It is found in two amino acids: cysteine and methionine.• Chlorine (symbol Cl) is a halogen. It is used as a disinfectant, especially in swimming pools.• Argon (symbol Ar) is a noble gas, making it almost entirely nonreactive. Incandescent lamps are often filled with

noble gasses such as argon in order to preserve the filaments at high temperatures.

Chemical elements in the fourth period

Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Atomic numberName

19K

20Ca

21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

31Ga

32Ge

33As

34Se

35Br

36Kr

electronconfiguration

all begin with [Ar]

4s1 4s2 3d1

4s23d2

4s23d3

4s23d5

4s13d5

4s23d6

4s23d7

4s23d8

4s23d10

4s13d10

4s23d10

4s2

4p1

3d10

4s2

4p2

3d10

4s2

4p3

3d10

4s2

4p4

3d10

4s2

4p5

3d10

4s2

4p6

From left to right, aqueous solutions of: Co(NO3)2 (red); K2Cr2O7(orange); K2CrO4 (yellow); NiCl2 (green); CuSO4 (blue); KMnO4

(purple).

Period 4 includes the biologically essential elementspotassium and calcium, and is the first period in thed-block with the lighter transition metals. These includeiron, the heaviest element forged in main-sequencestars and a principal component of the earth, as well asother important metals such as cobalt, nickle, copper,and zinc. Almost all have biological roles.

Page 91: Periodic Table

Period 88

Chemical elements in the fifth period

Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

#Name

37Rb

38Sr

39Y

40Zr

41Nb

42Mo

43Tc

44Ru

45Rh

46Pd

47Ag

48Cd

49In

50Sn

51Sb

52Te

53I

54Xe

Period 5 includes the important metals silver and tin and the biologically important element iodine. Also in period 5is the lightest purely radioactive element, technetium, the first element to be artificially synthesized.

Chemical elements in the sixth period

Group 1 2 3 (Lanthanides) 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

#Name

55Cs

56Ba

57La

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

81Tl

82Pb

83Bi

84Po

85At

86Rn

Period 6 is the first period to include the F block, with the lanthanides aka rare earth elements, and includes theheaviest stable elements. Many of these heavy metals are toxic and some are radioactive, but platinum and gold arelargely inert.

Chemical elements in the seventh period

Group 1 2 3 (Actinides) 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

#Name

87Fr

88Ra

89Ac

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

104Rf

105Db

106Sg

107Bh

108Hs

109Mt

110Ds

111Rg

112Cn

113Uut

114Uuq

115Uup

116Uuh

117Uus

118Uuo

All elements of period 7 are radioactive. This period contains the heaviest element which occurs naturally on earth,uranium. Most of the subsequent elements in the period have been synthesized artificially. Whilst some of these (e.g.plutonium) are now available in tonne quantities, most are extremely rare, having only been prepared in microgramamounts or less. Some of the later elements have only ever been identified in laboratories in quantities of a fewatoms at a time.Although the rarity of many of these elements means that experimental results are not very extensive, periodic andgroup trends in behaviour appear to be less well defined for period 7 than for other periods. Whilst francium andradium do show typical properties of Groups 1 and 2 respectively, the actinides display a much greater variety ofbehaviour and oxidation states that than the lanthanides. Initial studies suggest Group 14 element ununquadiumappears to be a noble gas instead of a poor metal, and group 18 element ununoctium probably is not a noble gas.[18]

These peculiarities of period 7 may be due to a variety of factors, including a large degree of spin-orbit coupling andrelativistic effects, ultimately caused by the very high positive electrical charge from their massive atomic nuclei.

Chemical elements in the eighth periodNo element of the eighth period has yet been synthesized. A G block is predicted. It is not clear if all elementspredicted for the eighth period are in fact physically possible. There may therefore be no ninth period.

Element categories in the periodic table

Page 92: Periodic Table

Period 89

Metals Metalloids Nonmetals UnknownchemicalpropertiesAlkali

metalsAlkaline

earth metalsInner transition

elementsTransitionelements

Othermetals

Othernonmetals

Halogens Noblegases

Lanthanides Actinides

References[1] Palmer, David (November 13, 1997). "Hydrogen in the Universe" (http:/ / imagine. gsfc. nasa. gov/ docs/ ask_astro/ answers/ 971113i. html).

NASA. . Retrieved 2008-02-05.[2] "hydrogen". Encyclopædia Britannica. 2008.[3] "Helium: physical properties" (http:/ / www. webelements. com/ helium/ physics. html). WebElements. . Retrieved 2008-07-15.[4] "Helium: geological information" (http:/ / www. webelements. com/ helium/ geology. html). WebElements. . Retrieved 2008-07-15.[5] Cox, Tony (1990-02-03). "Origin of the chemical elements" (http:/ / www. newscientist. com/ article/ mg12517027.

000-origin-of-the-chemical-elements. html). New Scientist. . Retrieved 2008-07-15.[6] "Helium supply deflated: production shortages mean some industries and partygoers must squeak by.". Houston Chronicle. 2006-11-05.[7] Brown, David (2008-02-02). "Helium a New Target in New Mexico" (http:/ / www. aapg. org/ explorer/ 2008/ 02feb/ helium. cfm). American

Association of Petroleum Geologists. . Retrieved 2008-07-15.[8] Lithium (http:/ / www. webelements. com/ lithium/ ) at WebElements.[9] "IARC Monograph, Volume 58" (http:/ / www. inchem. org/ documents/ iarc/ vol58/ mono58-1. html). International Agency for Research on

Cancer. 1993. . Retrieved 2008-09-18.[10] Information (http:/ / www. chronicberylliumdisease. com/ medical/ med_bediseases. htm#cbd) about chronic beryllium disease.[11] "Functions of Boron in Plant Nutrition" (http:/ / www. borax. com/ agriculture/ files/ an203. pdf) (PDF). U.S. Borax Inc.. .[12] Blevins, Dale G.; Lukaszewski, Krystyna M. (1998). "Functions of Boron in Plant Nutrition". Annual Review of Plant Physiology and Plant

Molecular Biology 49: 481–500. doi:10.1146/annurev.arplant.49.1.481. PMID 15012243.[13] Ten most abundant elements in the universe, taken from The Top 10 of Everything, 2006, Russell Ash, page 10. Retrieved October 15, 2008.

(http:/ / plymouthlibrary. org/ faqelements. htm)[14] Chang, Raymond (2007). Chemistry, Ninth Edition. McGraw-Hill. pp. 52. ISBN 0-07-110595-6.[15] Freitas Jr., Robert A. (1999). Nanomedicine (http:/ / www. foresight. org/ Nanomedicine/ Ch03_1. html),. Landes Bioscience. Tables 3-1 &

3-2. ISBN 1570596808.[16] "Structure and Nomenclature of Hydrocarbons" (http:/ / chemed. chem. purdue. edu/ genchem/ topicreview/ bp/ 1organic/ organic. html).

Purdue University. . Retrieved 2008-03-23.[17] Alberts, Bruce; Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, Peter Walter. Molecular Biology of the Cell (http:/ / www.

ncbi. nlm. nih. gov/ books/ bv. fcgi?highlight=carbon& rid=mboc4. section. 165). Garland Science. .[18] See references in the articles Ununquadium, Ununoctium

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Pediod 1 90

Pediod 1A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the chemicalelements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour ofthe elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat,meaning that elements with similar behaviour fall into the same vertical columns. The first period contains fewerelements than any other row in the table, with only two: hydrogen and helium. This situation can be explained bymodern theories of atomic structure.

Elements

HydrogenHydrogen (H) is the chemical element with atomic number 1. At standard temperature and pressure, hydrogen is acolorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H2. With anatomic mass of 1.00794 amu, hydrogen is the lightest element.[1]

Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elementalmass.[2] Stars in the main sequence are mainly composed of hydrogen in its plasma state. Elemental hydrogen isrelatively rare on Earth, and is industrially produced from hydrocarbons such as methane, after which most elementalhydrogen is used "captively" (meaning locally at the production site), with the largest markets almost equally dividedbetween fossil fuel upgrading, such as hydrocracking, and ammonia production, mostly for the fertilizer market.Hydrogen may be produced from water using the process of electrolysis, but this process is significantly moreexpensive commercially than hydrogen production from natural gas.[3]

The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and noneutrons.[4] In ionic compounds, it can take on either a positive charge, becoming a cation composed of a bareproton, or a negative charge, becoming an anion known as a hydride. Hydrogen can form compounds with mostelements and is present in water and most organic compounds.[5] It plays a particularly important role in acid-basechemistry, in which many reactions involve the exchange of protons between soluble molecules.[6] As the onlyneutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and spectrum ofthe hydrogen atom has played a key role in the development of quantum mechanics.[7]

The interactions of hydrogen with various metals are very important in metallurgy, as many metals can sufferhydrogen embrittlement,[8] and in developing safe ways to store it for use as a fuel.[9] Hydrogen is highly soluble inmany compounds composed of rare earth metals and transition metals[10] and can be dissolved in both crystalline andamorphous metals.[11] Hydrogen solubility in metals is influenced by local distortions or impurities in the metalcrystal lattice.[12]

HeliumHelium (He) is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gasseries in the periodic table and whose atomic number is 2.[13] Its boiling and melting points are the lowest among theelements and it exists only as a gas except in extreme conditions.[14]

Helium was discovered in 1868 by French astronomer Pierre Janssen, who first detected the substance as an unknown yellow spectral line signature in light from a solar eclipse.[15] In 1903, large reserves of helium were found in the natural gas fields of the United States, which is by far the largest supplier of the gas.[16] The substance is used in cryogenics,[17] in deep-sea breathing systems,[18] to cool superconducting magnets, in helium dating,[19] for inflating balloons,[20] for providing lift in airships,[21] and as a protective gas for industrial uses such as arc welding and growing silicon wafers.[22] Inhaling a small volume of the gas temporarily changes the timbre and quality of the

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human voice.[23] The behavior of liquid helium-4's two fluid phases, helium I and helium II, is important toresearchers studying quantum mechanics and the phenomenon of superfluidity in particular,[24] and to those lookingat the effects that temperatures near absolute zero have on matter, such as with superconductivity.[25]

Helium is the second lightest element and is the second most abundant in the observable universe.[26] Most heliumwas formed during the Big Bang, but new helium is being created as a result of the nuclear fusion of hydrogen instars.[27] On Earth, helium is relatively rare and is created by the natural decay of some radioactive elements[28]

because the alpha particles that are emitted consist of helium nuclei. This radiogenic helium is trapped with naturalgas in concentrations of up to seven percent by volume,[29] from which it is extracted commercially by alow-temperature separation process called fractional distillation.[30]

References• Bloch, D. R. (2006). Organic Chemistry Demystified [31]. McGraw-Hill Professional. ISBN 0-07-145920-0.

References[1] "Hydrogen – Energy" (http:/ / www. eia. doe. gov/ kids/ energyfacts/ sources/ IntermediateHydrogen. html). Energy Information

Administration. . Retrieved 2008-07-15.[2] Palmer, David (November 13, 1997). "Hydrogen in the Universe" (http:/ / imagine. gsfc. nasa. gov/ docs/ ask_astro/ answers/ 971113i. html).

NASA. . Retrieved 2008-02-05.[3] Staff (2007). "Hydrogen Basics — Production" (http:/ / www. fsec. ucf. edu/ en/ consumer/ hydrogen/ basics/ production. htm). Florida Solar

Energy Center. . Retrieved 2008-02-05.[4] Sullivan, Walter (1971-03-11). "Fusion Power Is Still Facing Formidable Difficulties". The New York Times.[5] "hydrogen". Encyclopædia Britannica. 2008.[6] Eustis, S. N.; Radisic, D; Bowen, KH; Bachorz, RA; Haranczyk, M; Schenter, GK; Gutowski, M (2008-02-15). "Electron-Driven Acid-Base

Chemistry: Proton Transfer from Hydrogen Chloride to Ammonia". Science 319 (5865): 936–939. doi:10.1126/science.1151614.PMID 18276886.

[7] "Time-dependent Schrödinger equation". Encyclopædia Britannica. 2008.[8] Rogers, H. C. (1999). "Hydrogen Embrittlement of Metals". Science 159 (3819): 1057–1064. doi:10.1126/science.159.3819.1057.

PMID 17775040.[9] Christensen, C. H.; Nørskov, J. K.; Johannessen, T. (July 9, 2005). "Making society independent of fossil fuels — Danish researchers reveal

new technology" (http:/ / www. dtu. dk/ English/ About_DTU/ News. aspx?guid={E6FF7D39-1EDD-41A4-BC9A-20455C2CF1A7}).Technical University of Denmark. . Retrieved 2008-03-28.

[10] Takeshita, T.; Wallace, W.E.; Craig, R.S. (1974). "Hydrogen solubility in 1:5 compounds between yttrium or thorium and nickel or cobalt".Inorganic Chemistry 13 (9): 2282–2283. doi:10.1021/ic50139a050.

[11] Kirchheim, R.; Mutschele, T.; Kieninger, W (1988). "Hydrogen in amorphous and nanocrystalline metals". Materials Science andEngineering 99: 457–462. doi:10.1016/0025-5416(88)90377-1.

[12] Kirchheim, R. (1988). "Hydrogen solubility and diffusivity in defective and amorphous metals". Progress in Materials Science 32 (4):262–325. doi:10.1016/0079-6425(88)90010-2.

[13] "Helium: the essentials" (http:/ / www. webelements. com/ helium/ ). WebElements. . Retrieved 2008-07-15.[14] "Helium: physical properties" (http:/ / www. webelements. com/ helium/ physics. html). WebElements. . Retrieved 2008-07-15.[15] "Pierre Janssen" (http:/ / encarta. msn. com/ encyclopedia_762508746/ pierre_janssen. html). MSN Encarta. . Retrieved 2008-07-15.[16] Theiss, Leslie (2007-01-18). "Where Has All the Helium Gone?" (http:/ / www. blm. gov/ wo/ st/ en/ info/ newsroom/ 2007/ january/

NR0701_2. html). Bureau of Land Management. . Retrieved 2008-07-15.[17] Timmerhaus, Klaus D. (2006-10-06). Cryogenic Engineering: Fifty Years of Progress. Springer. ISBN 0-387-33324-X.[18] Copel, M. (September 1966). "Helium voice unscrambling". Audio and Electroacoustics 14 (3): 122–126. doi:10.1109/TAU.1966.1161862.[19] "helium dating". Encyclopædia Britannica. 2008.[20] Brain, Marshall. "How Helium Balloons Work" (http:/ / www. howstuffworks. com/ helium. htm). How Stuff Works. . Retrieved

2008-07-15.[21] Jiwatram, Jaya (2008-07-10). "The Return of the Blimp" (http:/ / www. popsci. com/ military-aviation-space/ article/ 2008-07/

return-blimp). Popular Science. . Retrieved 2008-07-15.[22] "When good GTAW arcs drift; drafty conditions are bad for welders and their GTAW arcs.". Welding Design & Fabrication. 2005-02-01.[23] Montgomery, Craig (2006-09-04). "Why does inhaling helium make one's voice sound strange?" (http:/ / www. sciam. com/ article.

cfm?id=why-does-inhaling-helium). Scientific American. . Retrieved 2008-07-15.[24] "Probable Discovery Of A New, Supersolid, Phase Of Matter" (http:/ / www. sciencedaily. com/ releases/ 2004/ 09/ 040903085531. htm).

Science Daily. 2004-09-03. . Retrieved 2008-07-15.

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[25] Browne, Malcolm W. (1979-08-21). "Scientists See Peril In Wasting Helium; Scientists See Peril in Waste of Helium". The New YorkTimes.

[26] "Helium: geological information" (http:/ / www. webelements. com/ helium/ geology. html). WebElements. . Retrieved 2008-07-15.[27] Cox, Tony (1990-02-03). "Origin of the chemical elements" (http:/ / www. newscientist. com/ article/ mg12517027.

000-origin-of-the-chemical-elements. html). New Scientist. . Retrieved 2008-07-15.[28] "Helium supply deflated: production shortages mean some industries and partygoers must squeak by.". Houston Chronicle. 2006-11-05.[29] Brown, David (2008-02-02). "Helium a New Target in New Mexico" (http:/ / www. aapg. org/ explorer/ 2008/ 02feb/ helium. cfm).

American Association of Petroleum Geologists. . Retrieved 2008-07-15.[30] Voth, Greg (2006-12-01). "Where Do We Get the Helium We Use?". The Science Teacher.[31] http:/ / books. google. com/ ?id=yVPcSIn5xjAC

ExtensionsThere are currently seven periods in the periodic table of chemical elements, culminating with atomic number 118. Iffurther elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laidout (as with the existing periods) to illustrate periodically recurring trends in the properties of the elementsconcerned. Any additional periods are expected to contain a larger number of elements than the seventh period, asthey are calculated to have an additional so-called g-block, containing 18 elements with partially filled g-orbitals ineach period. An eight-period table containing this block was suggested by Glenn T. Seaborg in 1969.[1]

No elements in this region have been synthesized or discovered in nature. (Element 122 was claimed to existnaturally in April 2008, but this claim was widely believed to be erroneous.)[2] The first element of the g-block mayhave atomic number 121, and thus would have the systematic name unbiunium. Elements in this region are likely tobe highly unstable with respect to radioactive decay, and have extremely short half lives, although element 126 ishypothesized to be within an island of stability that is resistant to fission but not to alpha decay. It is not clear howmany elements beyond the expected island of stability are physically possible, if period 8 is complete, or if there is aperiod 9. If period 9 does exist, it is likely to be the last.According to the orbital approximation in quantum mechanical descriptions of atomic structure, the g-block wouldcorrespond to elements with partially-filled g-orbitals. However, spin-orbit coupling effects reduce the validity of theorbital approximation substantially for elements of high atomic number.[3]

Extended periodic table, including the g-block

Extended Periodic Table[4]

1 1

H

2

He

2 3

Li

4

Be

5

B

6

C

7

N

8

O

9

F

10

Ne

3 11

Na

12

Mg

13

Al

14

Si

15

P

16

S

17

Cl

18

Ar

4 19

K

20

Ca

21

Sc

22

Ti

23

V

24

Cr

25

Mn

26

Fe

27

Co

28

Ni

29

Cu

30

Zn

31

Ga

32

Ge

33

As

34

Se

35

Br

36

Kr

5 37

Rb

38

Sr

39

Y

40

Zr

41

Nb

42

Mo

43

Tc

44

Ru

45

Rh

46

Pd

47

Ag

48

Cd

49

In

50

Sn

51

Sb

52

Te

53

I

54

Xe

6 55

Cs

56

Ba

57

La

58

Ce

59

Pr

60

Nd

61

Pm

62

Sm

63

Eu

64

Gd

65

Tb

66

Dy

67

Ho

68

Er

69

Tm

70

Yb

71

Lu

72

Hf

73

Ta

74

W

75

Re

76

Os

77

Ir

78

Pt

79

Au

80

Hg

81

Tl

82

Pb

83

Bi

84

Po

85

At

86

Rn

7 87

Fr

88

Ra

89

Ac

90

Th

91

Pa

92

U

93

Np

94

Pu

95

Am

96

Cm

97

Bk

98

Cf

99

Es

100

Fm

101

Md

102

No

103

Lr

104

Rf

105

Db

106

Sg

107

Bh

108

Hs

109

Mt

110

Ds

111

Rg

112

Cn

113

Uut

114

Uuq

115

Uup

116

Uuh

117

Uus

118

Uuo

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Extensions 93

8 119

Uue

120

Ubn

121

Ubu

122

Ubb

123

Ubt

124

Ubq

125

Ubp

126

Ubh

127

Ubs

128

Ubo

129

Ube

130

Utn

131

Utu

132

Utb

133

Utt

134

Utq

135

Utp

136

Uth

137

Uts

138

Uto

139

Ute

140

Uqn

141

Uqu

142

Uqb

143

Uqt

144

Uqq

145

Uqp

146

Uqh

147

Uqs

148

Uqo

149

Uqe

150

Upn

151

Upu

152

Upb

153

Upt

154

Upq

155

Upp

156

Uph

157

Ups

158

Upo

159

Upe

160

Uhn

161

Uhu

162

Uhb

163

Uht

164

Uhq

165

Uhp

166

Uhh

167

Uhs

168

Uho

9 169

Uhe

170

Usn

171

Usu

172

Usb

173

Ust

Blocks of the periodic table

s-block p-block d-block f-block  g-block

(Undiscovered (theorized) elements are coloured in a lighter shade)

All of these hypothetical undiscovered elements are named by the International Union of Pure and AppliedChemistry (IUPAC) systematic element name standard which creates a generic name for use until the element hasbeen discovered, confirmed, and an official name approved.The positioning of the g-block in the table (to the left of the f-block, to the right, or in between) is speculative. Thepositions shown in the table above corresponds to the assumption that the Madelung rule will continue to hold athigher atomic number; this assumption may or may not be true. At element 118, the orbitals 1s, 2s, 2p, 3s, 3p, 3d, 4s,4p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 7s and 7p are assumed to be filled, with the remaining orbitals unfilled. Theorbitals of the eighth period are predicted to be filled in the order 8s, 5g, 6f, 7d, 8p. However, after approximatelyelement 120, the proximity of the electron shells makes placement in a simple table problematic; for example,calculations suggest that it may be elements 165 and 166 which occupy the 9s block (leaving the 8p orbitalincomplete) assuming they are physically possible.[5]

End of the periodic tableThe number of physically possible elements is unknown. The light-speed limit on electrons orbiting in ever-biggerelectron shells theoretically limits neutral atoms to a Z of approximately 173,[6] after which it would be nonsensicalto assign the elements to blocks on the basis of electron configuration. However, it is likely that the periodic tableactually ends much earlier, possibly soon after the island of stability,[7] which is expected to center around Z =126.[8]

Additionally the extension of the periodic and nuclides tables is restricted by the proton drip line and the neutron dripline.

Bohr model breakdownThe Bohr model exhibits difficulty for atoms with atomic number greater than 137, for the speed of an electron in a1s electron orbital, v, is given by

where Z is the atomic number, and α is the fine structure constant, a measure of the strength of electromagneticinteractions.[9] Under this approximation, any element with an atomic number of greater than 137 would require 1selectrons to be traveling swifter than c, the speed of light. Hence a non-relativistic model such as the Bohr model isinadequate for such calculations.

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Extensions 94

The Dirac equationThe semi-relativistic Dirac equation also has problems for Z > 137, for the ground state energy is

where m0 is the rest mass of the electron. For Z > 137, the wave function of the Dirac ground state is oscillatory,rather than bound, and there is no gap between the positive and negative energy spectra, as in the Klein paradox.[10]

Richard Feynman pointed out this effect, so the last element expected under this model, 137 (untriseptium), issometimes called feynmanium.However, a realistic calculation has to take into account the finite extension of the nuclear-charge distribution. Thisresults in a critical Z of ≈ 173 (unseptrium), such that non-ionized atoms may be limited to elements equal to orlower than this.[6]

See also• Electron configuration• Nuclear shell model• Table of nuclides (combined)

References[1] (http:/ / acs. lbl. gov/ Seaborg. talks/ 65th-anniv/ 29. html)[2] "Heaviest element claim criticised" (http:/ / www. rsc. org/ chemistryworld/ News/ 2008/ May/ 02050802. asp). Rsc.org. 2008-05-02. .

Retrieved 2010-03-16.[3] For example, an element in the column labeled g1 may indeed have exactly one valence-shell g-electron (as the name suggests), but it is also

possible that it would have more, or none at all.[4] The labels "g1", etc. are inspired by the Madelung rule, but this is merely an empirical rule, with well-known exceptions such as copper.[5] Pekka Pyykkö, Peter Schwerdtfeger (2004), Relativistic electronic structure theory, p 23.[6] Walter Greiner and Stefan Schramm (2008). American Journal of Physics 76: 509. doi:10.1119/1.2820395., and references therein.[7] Encyclopædia Britannica. "transuranium element (chemical element) - Britannica Online Encyclopedia" (http:/ / www. britannica. com/

EBchecked/ topic/ 603220/ transuranium-element). Britannica.com. . Retrieved 2010-03-16.[8] S. Cwiok, P.-H. Heenen and W. Nazarewicz (2005). "Shape coexistence and triaxiality in the superheavy nuclei". Nature 433: 705.[9] See for example R. Eisberg and R. Resnick, Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles, Wiley (New York: 1985).[10] James D. Bjorken and Sidney D. Drell, Relativistic Quantum Mechanics, McGraw-Hill (New York:1964).

• http:/ / www. springerlink. com/ content/ j303171428652143/

External links• Images of g-orbitals (http:/ / www. uky. edu/ ~holler/ html/ g. html) from the University of Kentucky• jeries.rihani.com (http:/ / jeries. rihani. com) - The extended periodic table of the elements.• Eric Scerri, The Periodic Table, Its Story and Its Significance, Oxford University Press, 2007.

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95

Blocks

BlockA block of the periodic table of elements is a set of adjacent groups. The term appears to have been first used (inFrench) by Charles Janet. [1] The respective highest-energy electrons in each element in a block belong to the sameatomic orbital type. Each block is named after its characteristic orbital; thus, the blocks are:• s-block• p-block• d-block• f-block• g-block (hypothetical)The block names (s, p, d, f. and g) are derived from the quality of the spectroscopic lines of the associated atomicorbitals: sharp, principal, diffuse and fundamental, the rest being named in alphabetical order. Blocks are sometimescalled families.[1] Charles Janet, La classification helicoidal des elements chimiques, Beauvais, 1928

s-block

Chemical elements in s-block

Group 1 2 18

Period

1 1H

2He

2 3Li

4Be

3 11Na

12Mg

4 19K

20Ca

5 37Rb

38Sr

6 55Cs

56Ba

7 87Fr

88Ra

The s-block of the periodic table of elements consists of the first two groups: the alkali metals and alkaline earthmetals, plus hydrogen and helium.These elements are distinguished by the property that in the atomic ground state, the highest-energy electron is in an s-orbital. Except in hydrogen and helium, these electrons are very easily lost to form positive ions. The helium

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s-block 96

configuration is chemically exceedingly stable and thus helium has no known stable compounds; thus it is generallygrouped with the noble gases.The other elements of the s-block are all extremely powerful reducing agents, so much so that they never occurnaturally in the free state. The metallic forms of these elements can only be extracted by electrolysis of a molten salt,since water is much more easily reduced to hydrogen than the ions of these metals. Sir Humphry Davy, in 1807 and1808, was the first to isolate all of these metals except lithium, beryllium, rubidium and caesium. Beryllium wasisolated independently by F. Wooler and A.A. Bussy in 1828, while lithium was isolated by Robert Bunsen in 1854,who isolated rubidium nine years later after having observed it and caesium spectroscopically. Caesium was notisolated until 1881 when Carl Setterberg electrolysed the molten cyanide.The s-block metals vary from extremely soft (all the alkali metals) to quite hard (beryllium). With the exception ofberyllium and magnesium, the metals are too reactive for any structural use except as very minor components (<2%)of alloys with lead. Beryllium and magnesium, though very expensive, are valuable for uses that require strength andlightness. They are extremely valuable as reducing agents to extract titanium, zirconium, thorium and tantalum fromtheir ores, and have other uses as reducing agents in organic chemistry.All the s-block metals are dangerous fire hazards which require special extinguishants to extinguish, except forberyllium and magnesium, storage must be under either argon or an inert liquid hydrocarbon. They react vigorouslywith water to liberate hydrogen, except for magnesium, which reacts slowly, and beryllium, which reacts only whenamalgamated with mercury to destroy the oxide film. Lithium has similar properties to magnesium due to thediagonal relationship with magnesium in the periodic table.

See also• Electron configuration

p-block

Chemical elements in p-block

Group 13 14 15 16 17 18

Period

2 5B

6C

7N

8O

9F

10Ne

3 13Al

14Si

15P

16S

17Cl

18Ar

4 31Ga

32Ge

33As

34Se

35Br

36Kr

5 49In

50Sn

51Sb

52Te

53I

54Xe

6 81Tl

82Pb

83Bi

84Po

85At

86Rn

7 113Uut

114Uuq

115Uup

116Uuh

117Uus

118Uuo

The p-block of the periodic table of the elements consists of the last six groups minus helium (which is located in the s-block). In the elemental form of the p-block elements, the highest energy electron occupies a p-orbital. The p-block contains all of the nonmetals (except for Hydrogen and Helium which are in the s-block) and semimetals, as well as

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p-block 97

some of the metals.The groups of the p-block are:• 13 (IIIB,IIIA): Boron Group• 14 (IVB,IVA): Carbon Group• 15 (VB,VA): Nitrogen Group• 16 (VIB,VIA): Chalcogens• 17 (VIIB,VIIA): Halogens• 18 (Group 0): Noble gases (excluding Helium)

See also• Electron configuration

Explanation of above periodic table slice:

atomic numberin red are gases

atomic number inblack are solids

atomic number ingreen are liquids

solid borders are primordialelements (older than the

Earth)

dotted borders areradioactive, synthetic

elements

dashed borders have noisotopes older than the

earth

d-blockThe d-block is a the portion of the periodic table which contains the element groups 3-12.[1] [2] These groupscorrespond to the filling of the atomic d-orbital subshell, with electron configurations ranging from s2d1 (Group 3) tos2d10 (Group 12). There are however some irregularities in the sequence; for example Cr is s1d5 (not s2d4) and theGroup 11 metals are s1d10 (not s2d9), so that the d-subshell is actually complete at Group 11.The d-block elements are often also known as transition metals or transition elements. However the exact limits ofthe transition metal region are usually not considered to be identical to the d-block. Although some authors doidentify the entire d-block as transition metals[1] , most define transition metals as elements with partly filled dsubshells either in the neutral atom or in ions in common oxidation states.[2] [3] This definition has now been adoptedby IUPAC[4] and corresponds to including only Groups 3-11 as transition metals. Group 12 metals lack thecharacteristic chemical and physical properties associated with incomplete d subshells and are consideredpost-transition metals. Jensen has reviewed the historical usage of the terms transition element (or metal) andd-block.[5]

In the s-block and p-block of the periodic table, similar properties across the periods are generally not observed: themost important similarities tend to be vertical, down groups. However the d-block is notable in that horizontalsimilarities across the periods do become important.Although Lutetium and Lawrencium are in the d-block, they are not considered transition metals but a lanthanideand an actinide, respectively, according to IUPAC.[6] Group 12 elements are also in the d-block but are consideredpost-transition metals as their d-subshell is completely filled.[6]

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d-block 98

Chemical elements in d-block

Group → 3 4 5 6 7 8 9 10 11 12

↓ Period

4 21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

5 39Y

40Zr

41Nb

42Mo

43Tc

44Ru

45Rh

46Pd

47Ag

48Cd

6 71Lu

72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

7 103Lr

104Rf

105Db

106Sg

107Bh

108Hs

109Mt

110Ds

111Rg

112Cn

A Way to learn 3d elements:

SupremeCourt - Sc

Tied - Ti

Various - V

CriMinals - Cr,Mn

For - Fe

Controlling - Co

Night - Ni

Club - Cu

Zones - Zn

See also• Electron configuration

References[1] R.H. Petrucci, W.S. Harwood and F.G. Herring “General Chemistry” (8th ed, Prentice-Hall 2002), p.341-2[2] C.E. Housecroft and A.G. Sharpe “Inorganic Chemistry” (2nd ed, Pearson Prentice-Hall 2005), p..20-21[3] F.A. Cotton and G. Wilkinson “Advanced Inorganic Chemistry” (5th ed, John Wiley 1988) p.625[4] International Union of Pure and Applied Chemistry. " transition element (http:/ / goldbook. iupac. org/ T06456. html)". Compendium of

Chemical Terminology Internet edition.[5] Jensen, William B. (2003). "The Place of Zinc, Cadmium, and Mercury in the Periodic Table" (http:/ / www. uv. es/ ~borrasj/ ingenieria_web/

temas/ tema_1/ lecturas_comp/ p952. pdf). Journal of Chemical Education 80 (8): 952–961. doi:10.1021/ed080p952. .[6] IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (http:/ / www. iupac. org/ reports/ provisional/

abstract04/ connelly_310804. html) (online draft of an updated version of the "Red Book" IR 3-6)

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f-block 99

f-blockThe f-block of the periodic table of the elements consists of those elements whose atoms or ions have valenceelectrons in f-orbitals. Actual electronic configurations may be slightly different from what is predicted by theaufbau principle. The elements are also known as inner transition elements. There are two series. Elements of theseries in which the electrons are in 4f orbitals belong to the lanthanoid series. Elements of the series in which theelectrons are in 5f orbitals belong to the actinoid series. There is a long-standing controversy as to whether La andAc or Lu and Lr should belong to the f-block. IUPAC has now compromised by putting all four elements into theblock, but this is contested, because there can only be 14 elements in f orbitals, so the block cannot be 15 elementswide. [1]

f-block

Lanthanoids 57La

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

Actinoids 89Ac

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

All elements in the lanthanide series form M3+ ions. In aqueous solution the early lanthanides are surrounded by ninewater molecules while the later lanthanides have a coordination number of 8. Cerium also forms compounds with the+4 oxidation state; Ce4+ has the very stable electronic configuration of the noble gas Xe. Ce(IV) is a strong oxidisingagent. Eu2+ has the configuration [Xe]4f7 and is a strong reducing agent. The existence of Eu(II) is attributed to thestability of the half-filled f-shell.[2]

The lighter actinides (uranium to americium) show oxidation states of +3, +4, +5 and +6. The later actinidesresemble the lanthanides in that the +3 oxidation state is favoured.

See also• Electron configuration

External links• Images of f-orbitals [3]

• Interactive f-orbital models can be found at this site:[4]

References[1] f-block stands for fundamental-block. IUPAC Periodic Table 2007 .pdf (http:/ / www. iupac. org/ reports/ periodic_table/

IUPAC_Periodic_Table-22Jun07b. pdf)[2] Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419

Chapters 30 and 31[3] http:/ / www. uky. edu/ ~holler/ html/ f. html[4] http:/ / www. d. umn. edu/ ~pkiprof/ ChemWebV2/ AOs/ ao4. html

Page 103: Periodic Table

100

Other divisions

ActinideThe actinide or actinoid (IUPAC nomenclature) series encompasses the 14 chemical elements with atomic numbersfrom 90 to 103, thorium to lawrencium.[1] [2] [3] The actinide series derives its name from the group 3 elementactinium which can be included in the series for the purpose of comparisons. Only thorium and uranium occur inusable quantities in nature. The other actinides are man-made elements. The actinides are usually considered to bef-block elements. The actinides show much more variable valency than the lanthanoids. All actinides are radioactive.

HistoryPrior to 1945, it was generally thought, following Mendeleev, that thorium and uranium were transition metals ingroups 4 and 6 respectively. The assumption was that the transuranium elements would also have the properties oftransition metals. However, Charles Janet proposed in 1928 that, starting with actinium, there would be 14 elementscorresponding with the lanthanides. The transuranium elements were first synthesized as part of the ManhattanProject in around 1944. Glenn T. Seaborg, the principal investigator, found that americium and curium did not havethe properties to be expected of transition elements.[4] In 1945, he went against the advice of colleagues and, withoutknowing of Janet, adopted his proposal, which thus became the most significant change to the periodic table to havebeen accepted universally by the scientific community: that the actinide elements belong to a new series, similar tothe lanthanide series in that the valence electrons would be situated in f orbitals. This is also in accord with theAufbau principle which predicts that 5f orbitals will be filled before 6d orbitals.

Chemistry

AtomicNo.

89 90 91 92 93 94 95 96 97 98 99 100 101 102 103

Name Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Atoms 7s26d1 7s26d2 7s25f26d1 7s25f36d1 7s25f46d1 7s25f6 7s25f7 7s25f76d1 7s25f9 7s25f10 7s25f11 7s25f12 7s25f13 7s25f14 7s25f147p1

Some actinide atoms have electrons in 6d orbitals, but in compounds the 6s electrons and any d electrons are lost,leaving the ions with an electronic configuration [Rn]5fn. In this respect the actinides are similar to the lanthanoids,with only f electrons in the valence shell in compounds. There is also a similarity in the fact that the maximumoxidation state of the later actinides is +3. However, the early actinides, Th and U can lose all their valence electronsto achieve a maximum oxidation state of 4 and 6 respectively. Historically this led to some debate as to whetherthorium, and uranium should be considered as d-block elements, that is, with thorium in group 4, below hafnium,and uranium in group 6, below tungsten. The chemistry of these elements does in fact follow the trends expectedwith increasing atomic number going down those groups, taking into account the effects of the lanthanidecontraction. Np can also lose all its valence electrons, as in [NpO5]3-.The highest oxidation states of U, Np and Pu occur in covalent, mostly oxo- and fluoro compounds. For example, UF6 (mp 64oC) is sufficiently volatile to be used in gaseous diffusion or gas centrifuge isotope separation plants. All uranium (VI) compounds, apart from fluoro complexes and UO2, contain the linear "uranyl" group, UO2

2+. Between 4 to 6 ligands can be accommodated in an equatorial plane perpendicular to the uranyl group. The uranyl group acts as a hard acid and form stronger complexes with oxygen-donor ligands than with nitrogen-donor ligands. NpO2

2+

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Actinide 101

and PuO22+ are also the common form of Np and Pu in the +6 oxidation state.

Compound in the +5 and +4 oxidation states are also predominantly covalent. A notable feature of complexes ofactinides in the +4 oxidation state is that they can achieve coordination numbers as high as 11. Compounds in the +3oxidation state are semi-covalent. For example the trichlorides crystallize with ionic-type structures, but with clearevidence for some covalent bonding. Compounds of Th(III) and U(III) are very strong reducing agents, but thereducing power decreases from left to right along the actinide series, in line with the decreasing size.

The actinide contraction

Radii of 6-coordinate actinides in various oxidation states.[5]

The size of the actinides decreases with increasingatomic number. This is the normal periodic trend and issimilar to the lanthanide contraction. The trend isshown in each of the oxidation states +3, +4 and +5.

Colour and magnetism

Approximate colours of actinide ions in aqueous solution[6] [7]

Oxidationstate

89 90 91 92 93 94 95 96 97 98 99

+3 Ac3+ Th3+ Pa3+ U3+ Np3+ Pu3+ Am3+ Cm3+ Bk3+ Cf3+ Es3+

+4 Th4+ Pa4+ U4+ Np4+ Pu4+ Am4+ Cm4+ Bk4+ Cf4+

+5 PaO2+ UO

2+ NpO

2+ PuO

2+ AmO

2+

+6 UO22+ NpO

22+ PuO

22+ AmO

22+

+7 NpO23+ PuO

23+ [AmO

6]5-

The colours of the actinide ions in the lower oxidation states are due to f-f transitions. In the high oxidation statesthere may also be charge-transfer transitions. There is strong spin-orbit coupling, but weak crystal field splitting, sothere is little colour variation in compounds of a given element in a given oxidation state. Transitions between 5f and6d orbitals can be observed in the ultraviolet region of the spectrum. Magnetic moments of the paramagnetic speciesare far from spin-only values.

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Actinide 102

Organometallic chemistryAn organometallic compound of an actinide is known as an organoactinide. The organometallic chemistry of theactinides is not extensive. Uranocene, U(C8H8)2, is particularly interesting for the presence of the planar, Huckel rulearomatic cyclooctatrenyl anion, analogous to the cyclopentadenyl ion found in ferrocene. The formation of thiscompound is helped by the relative large size the U4+ ion.

Chemical aspects of radioactivityAll actinides are radioactive. Protactinium and all isotopes of the elements following uranium (the trans-uraniumelements) are man-made elements and have half-lives much less than the age of the earth and are not found in usablequantity in nature. Uranium and thorium are weak alpha emitters with very long half-lives and can be handled withminimum radiological protection procedures.Elements beyond einsteinium have not been synthesized in sufficient quantity to make detailed studies of theirchemistry.Radioactive decay is a significant source of heat, so temperature control is an issue with the trans-uranium elements.Also, emitted alpha particles can act as oxidizing agents. For example,

He2+ + H2O → 2H+ + 1/2 O2 + He

Occurrence

Actinides Half-life Fission products

244Cm 241Pu f 250Cf 243Cmf 10–30 y 137Cs 90Sr 85Kr

232U  f 238Pu f is forfissile

69–90 y 151Sm nc➔

4n 249Cf  f 242Amf 141–351 No fission producthas half-life 102

to 2×105 years241Am 251Cf  f 431–898

240Pu 229Th 246Cm 243Am 5–7 ky

4n 245Cmf 250Cm 239Pu f 8–24 ky

233U    f 230Th 231Pa 32–160

4n+1 234U 4n+3 211–290 99Tc 126Sn 79Se

248Cm 242Pu 340–373 Long-lived fission products

237Np 4n+2 1–2 my 93Zr 135Cs nc➔

236U 4n+1 247Cmf 6–23 107Pd 129I

244Pu 80 my >7% >5% >1% >.1%

232Th 238U 235U    f 0.7–12by fission product yield

Only thorium and uranium occur naturally in the Earth's crust in anything more than trace quantities. Protactiniumand actinium, which are both decay products of uranium, are the only remaining actinides that were discovered innature before they were synthesized. Neptunium and plutonium have also been known to show up naturally in traceamounts in uranium ores as a result of decay or bombardment, but this was only discovered after they weresynthesized. The remaining actinides were synthesized in particle colliders or nuclear reactors, and none of them hasbeen found to occur naturally on earth. Actinides beyond californium possess exceedingly short half-lives.

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Actinide 103

Isotopes of all of the transuranium elements up to and including fermium can be produced by rapid neutronbombardment of lighter nuclides. The nuclei created have an excess of neutrons. β-decay occurs with a neutrondecaying to a proton and an electron, increasing the atomic number in the process. Conditions suitable for thesynthesis of transuranium elements occur in supernovae. These elements may also be produced in specializednuclear reactors. They may be created in a nuclear explosion and come to earth as nuclear fallout from anatmospheric test explosion. The heavier elements may be synthesized by bombardment with heavier particles, suchas α particles or heavier nuclei.In 1961, Antoni Przybylski discovered a star, HD 101065, commonly called Przybylski's star, that contains unusuallyhigh amounts of actinides.

See also• Actinides in the environment

Further reading• Tamer Andrea and Moris S. Eisen (2008). "Recent advances in organothorium and organouranium catalysis".

Chem. Soc. Rev. 37: 550 - 567. doi:10.1039/b614969n.• Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, eds (2006). The Chemistry of the Actinide and

Transactinide Elements (3rd ed.). Dordrecht, The Netherlands: Springer. ISBN 13978-1-4020-3555-5.

External links• The Columbia Encyclopedia, Sixth Edition. [8]

• Chemical Elements website [9]

• Lawrence Berkeley Laboratory image of historic periodic table by Seaborg showing actinide series for the firsttime [10]

• Lawrence Livermore National Laboratory, Uncovering the Secrets of the Actinides [11]

• Los Alamos National Laboratory, Actinide Research Quarterly [12]

References[1] IUPAC Periodic Table (http:/ / www. iupac. org/ reports/ periodic_table)[2] IUPAC Periodic Table 2007 .pdf (http:/ / www. iupac. org/ reports/ periodic_table/ IUPAC_Periodic_Table-22Jun07b. pdf)[3] Connelly, Neil G.; et al. (2005). "Elements". Nomenclature of Inorganic Chemistry. London: Royal Society of Chemistry. pp. 52.[4] Seaborg, Glenn T. (1946). "The Transuranium Elements" (http:/ / www. jstor. org/ stable/ 1675046). Science 104 (2704): 379–386.

doi:10.1126/science.104.2704.379. .[5] Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419, p

1263[6] Arnold F. Holleman, Nils Wiberg: Lehrbuch der Anorganischen Chemie, 102. Auflage, de Gruyter, Berlin 2007, S. 1956; ISBN

978-3-11-017770-1.[7] dtv-Atlas zur Chemie 1981, Teil 1, S. 224.[8] http:/ / www. bartleby. com/ 65/ ac/ actinide. html[9] http:/ / www. chemicalelements. com/ groups/ rareearth. html[10] http:/ / imglib. lbl. gov/ ImgLib/ COLLECTIONS/ BERKELEY-LAB/ SEABORG-ARCHIVE/ index/ 96B05654. html[11] http:/ / www. llnl. gov/ str/ pdfs/ 06_00. 2. pdf#search=%22actinide%20series%22[12] http:/ / arq. lanl. gov/

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Lanthanide 104

LanthanideThe lanthanide or lanthanoid (IUPAC nomenclature)[1] series comprises the fourteen elements with atomicnumbers 58 through 71, from cerium to lutetium.[2] All lanthanides are f-block elements, corresponding to the fillingof the 4f electron shell. Lanthanum, which is a d-block element, may also be considered to be a lanthanide. Alllanthanide elements form trivalent cations, Ln3+, whose chemistry is largely determined by the ionic radius, whichdecreases steadily from lanthanum to lutetium.

Classification

Atomic No. 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

Name La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

M3+ f electrons 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

The lanthanide elements are the group of elements with atomic number increasing from 58 (cerium) to 71 (lutetium).They are termed lanthanide because the lighter elements in the series are chemically similar to lanthanum. Strictlyspeaking lanthanum is a group 3 element element and the ion La3+ has no f electrons. However this element is oftenincluded in any general discussion of the chemistry of the lanthanide elements.

ChemistryThe electronic structure of the lanthanide elements, with minor exceptions is [Xe]6s24fn. In their compounds, the 6selectrons are lost and the ions have the configuration [Xe]4fm.[3] The chemistry of the lanthanides differs from maingroup elements and transition metals because of the nature of the 4f orbitals. These orbitals are "buried" inside theatom and are shielded from the atom's environment by the 4d and 5p electrons. As a consequence of this thechemistry of the elements is largely determined by their size, which decreases gradually from 102 pm (La3+) withincreasing atomic number to 86 pm (Lu3+), the so-called lanthanide contraction. All the lanthanide elements exhibitthe oxidation state +3. In addition Ce3+ can lose its single f electron to form Ce4+ with the stable electronicconfiguration of xenon. Also, Eu3+ can gain an electron to form Eu2+ with the f7 configuration which has the extrastability of a half-filled shell. Promethium is effectively a man-made element as all its isotopes are radioactive withhalf-lives of less than 20 y.The similarity in ionic radius between adjacent lanthanide elements makes it difficult to separate them from eachother in naturally occurring ores and other mixtures. Historically the very laborious processes of cascading andfractional crystallization was used. Because the lanthanide ions have slightly different radii, the lattice energy oftheir salts and hydration energies of the ions will be slightly different, leading to a small difference in solubility.Salts of the formula Ln(NO3)3.2NH4NO3.4H2O can be used. Industrially, the elements are separated from each otherby solvent extraction. Typically an aqueous solution of nitrates is extracted into kerosene containingtri-n-butylphosphate, (BunO)3PO. The strength of the complexes formed increases as the ionic radius decreases, sosolubility in the organic phase increases. Complete separation can be achieved continuously by use of countercurrentexchange methods. The elements can also be separated by ion-exchange chromatography, making use of the fact thatthe stability constant for formation of EDTA complexes increases for log K ≈ 15.5 for [La(EDTA)]- to log K ≈ 19.8for [Lu(EDTA)]-.[4] The process, involving two columns, is described in detail in Greenwood & Earnshaw[5]

Ce(IV) is a useful oxidising agent, and Eu(II) is a useful reducing agent. The trivalent lanthanides mostly form ionic salts. The trivalent ions are hard acceptors and form more stable complexes with oxygen-donor ligands than with nitrogen-donor ligands. The larger ions are 9-coordinate in aqueous solution, [Ln(H2O)9]3+ but the smaller ions are 8-coordinate, [Ln(H2O)8]3+. There is some evidence that the later lanthanides have more water molecules in the

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Lanthanide 105

second coordination sphere.[6] Complexation with monodentate ligands is generally weak because it is difficult todisplace water molecules from the first coordination sphere. Stronger complexes are formed with chelating ligandsbecause of the chelate effect.

Magnetic and spectroscopic propertiesAll the trivalent lanthanide ions, except lutetium, have unpaired f electrons. However the magnetic moments deviateconsiderably from the spin-only values because of strong spin-orbit coupling. The maximum number of unpairedelectrons is 7, in Gd3+, with a magnetic moment of 7.94 B.M., but the largest magnetic moments, at 10.4-10.7 B.M.,are exhibited by Dy3+ and Ho3+. However, in Gd3+ all the electrons have parallel spin and this property is importantfor the use of gadolinium complexes as contrast reagent in MRI scans.

A solution of 4% holmium oxide in 10%perchloric acid, permanently fused into a quartz

cuvette as a wavelength calibration standard

Crystal field splitting is rather small for the lanthanide ions and is lessimportant than spin-orbit coupling in regard to energy levels.[7]

Transitions of electrons between f orbitals are forbidden by the Laporterule. Furthermore, because of the "buried" nature of the f orbitals,coupling with molecular vibrations is weak. Consequently the spectraof lanthanide ions are rather weak and the absorption bands aresimilarly narrow. Glass containing holmium oxide and holmium oxidesolutions (usually in perchloric acid) have sharp optical absorptionpeaks in the spectral range 200–900 nm and can be used as awavelength calibration standard for optical spectrophotometers[8] , andare available commercially.[9]

As f-f transitions are Laporte-forbidden, once an electron has been excited, decay to the ground state will be slow.This makes them suitable for use in lasers as it makes the population inversion easy to achieve. The Nd:YAG laser isone that is widely used. Lanthanide ions are also fluorescent as a result of the forbidden nature of f-f transitions.Europium-doped yttrium vanadate was the first red phosphor to enable the development of colour televisionscreens.[10]

Page 109: Periodic Table

Lanthanide 106

Organometallic chemistryMetal-carbon σ bonds are found in alkyls of the lanthanide elements such as [LnMe6]3- and Ln[CH(SiMe3)3].[11] Thecyclopentadiene complexes, of formula [Ln(C5H5)3] and [Ln(C5H5)2Cl] may have η-1, η-2, and η-5 rings.Analogues to uranocene are formed with the cyclo-octadienide ion, C8H8

2- which is a Hückel's rule aromatic ring.

Geochemistry

Abundance of elements in the Earth crust per million of Si atoms

The trivial name "rare earths" issometimes used to describe all thelanthanides together with scandiumand yttrium. This name arises from theminerals from which they wereisolated, which were uncommonoxide-type minerals. However, the useof the name is deprecated by IUPAC,as the elements are neither rare inabundance nor "earths" (an obsoleteterm for water-insoluble strongly basicoxides of electropositive metalsincapable of being smelted into metalusing late 18th century technology) .Cerium is the 26th most abundantelement in the Earth's crust,neodymium is more abundant thangold and even thulium (the leastcommon naturally occurring lanthanide) is more abundant than iodine.[12] Despite their abundance, even thetechnical term "lanthanides" could be interpreted to reflect a sense of elusiveness on the part of these elements, as itcomes from the Greek λανθανειν (lanthanein), "to lie hidden". However, if not referring to their natural abundance,but rather to their property of "hiding" behind each other in minerals, this interpretation is in fact appropriate. Theetymology of the term must be sought in the first discovery of lanthanum, at that time a so-called new rare earthelement "lying hidden" in a cerium mineral, but we might call it a fortunate twist of irony that exactly lanthanum waslater identified as the first in an entire series of chemically similar elements and could give name to the whole series.

The lanthanide contraction is responsible for the great geochemical divide that splits the lanthanides into light andheavy-lanthanide enriched minerals, the latter being almost inevitably associated with and dominated by yttrium.This divide is reflected in the first two "rare earths" that were discovered: yttria (1794) and ceria (1803). Thegeochemical divide has put more of the light lanthanides in the Earth's crust, but more of the heavy members in theEarth's mantle. The result is that although large rich ore-bodies are found that are enriched in the light lanthanides,correspondingly large ore-bodies for the heavy members are few. The principal ores are monazite and bastnaesite.Monazite sands usually contain all the lanthanide elements, but the heavier elements are lacking in bastnaesite. Thelanthanides obey the Oddo-Harkins rule - odd-numbered elements are less abundant than their even-numberedneighbours.Three of the lanthanide elements have radioactive isotopes with long half-lives (138La, 147Sm and 176Lu) that can beused to date minerals and rocks from Earth, the Moon and meteorites.[13]

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Lanthanide 107

Biological effectsLanthanides entering the human body due to exposure to various industrial processes can affect metabolic processes.Trivalent lanthanide ions, especially La3+ and Gd3+, can interfere with calcium channels in human and animal cells.Lanthanides can also alter or even inhibit the action of various enzymes. Lanthanide ions found in neurons canregulate synaptic transmission, as well as block some receptors (for example, glutamate receptors).[14]

ApplicationsMost lanthanides are widely used in lasers. These elements deflect ultraviolet and infrared radiation and arecommonly used in the production of sunglass lenses. Other applications are summarized in the following table:[12]

Application Percentage

Catalytic converters 45

Petroleum refining catalysts 25

Permanent magnets 12

Glass polishing andceramics

7

Metallurgical 7

Phosphors 3

Other 1

See also• Actinoid• Group 3 element• Lanthanide contraction• Rare earth element

External links• lanthanide Sparkle Model [15], used in the computational chemistry of lanthanoid complexes• USGS Rare Earths Statistics and Information [16]

• Ana de Bettencourt-Dias: Chemistry of the lanthanides and lanthanide-containing materials [17]

References[1] the current IUPAC recommendation is that the name lanthanoid be used rather than lanthanide, as the suffix "-ide" is preferred for negative

ions whereas the suffix "-oid" indicates similarity to one of the members of the containing family of elements. However, lanthanide is stillfavored in most (~90%) scientific articles and is currently adopted on wikipedia. In the older literature, the name "lanthanon" was often used.

[2] Holden, Norman E.; Coplen, Tyler (January-February 2004). The Periodic Table of the Elements (IUPAC) 26 (1): 8. http:/ / www. iupac. org/publications/ ci/ 2004/ 2601/ 2_holden. html. Retrieved March 23, 2010.

[3] Mark Winter. Lanthanum ionisation energies (http:/ / www. webelements. com/ lanthanum/ atoms. html). WebElements Ltd, UK. . Retrieved02-09-2010.

[4] L. Pettit and K. Powell, SC-database (http:/ / www. acadsoft. co. uk/ scdbase/ scdbase. htm)[5] Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419 p

1231[6] Burgess,, J. (1978). 'Metal ions in solution'. , New York: Ellis Horwood. ISBN 0853120277.[7] Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419 p

1242

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Lanthanide 108

[8] R. P. MacDonald (1964). "Uses for a Holmium Oxide Filter in Spectrophotometry" (http:/ / www. clinchem. org/ cgi/ reprint/ 10/ 12/ 1117.pdf). Clinical Chemistry 10: 1117. .

[9] "Holmium Glass Filter for Spectrophotometer Calibration" (http:/ / www. labshoponline. com/holmium-glass-filter-spectrophotometer-calibration-p-88. html). . Retrieved 2009-06-06.

[10] Levine, Albert K.; Palilla, Frank C. (1964). "A new, highly efficient red-emitting cathodoluminescent phosphor (YVO4:Eu) for colortelevision". Applied Physics Letters 5: 118. doi:10.1063/1.1723611.

[11] Cotton, S.A. (1997). "Aspects of the lanthanide-carbon σ-bond". Coord. Chem. Revs. 160: 93–127. doi:10.1016/S0010-8545(96)01340-9.[12] Helen C. Aspinall (2001). Chemistry of the f-block elements (http:/ / books. google. com/ ?id=bLI2maI1_xAC). CRC Press. p. 8.

ISBN 905699333X. .[13] There exist other naturally occurred radioactive isotopes of lanthanides with long half-lives (144Nd, 150Nd, 148Sm, 151Eu, 152Gd) but they are

not used as chronometers.[14] Pałasz, A; Czekaj, P (2000). "Toxicological and cytophysiological aspects of lanthanides action." (http:/ / www. actabp. pl/ pdf/ 4_2000/

1107-1114s. pdf). Acta biochimica Polonica 47 (4): 1107–14. PMID 11996100. .[15] http:/ / www. sparkle. pro. br[16] http:/ / minerals. usgs. gov/ minerals/ pubs/ commodity/ rare_earths/[17] http:/ / www. chem. unr. edu/ faculty/ abd/

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Metal 109

Metal

Alkali metals

Lithium, Sodium, Potassium

Rubidium, Caesium, Francium

Alkaline earth metals

Beryllium, Magnesium, Calcium

Strontium, Barium, Radium

Transition metals

Zinc, Molybdenum, Cadmium

Scandium, Titanium, Vanadium

Chromium, Manganese, Iron

Cobalt, Nickel, Copper

Yttrium, Zirconium, Niobium

Technetium, Ruthenium, Rhodium

Palladium, Silver, Hafnium

Tantalum, Tungsten, Rhenium

Osmium, Iridium, Platinum

Gold, Mercury, Rutherfordium,

Dubnium, Seaborgium, Bohrium,

Hassium, Meitnerium,

Darmstadtium, Roentgenium, Copernicium

Post-transition metals

Aluminium, Gallium, Indium

Tin, Thallium, Lead, Bismuth

Ununtrium, Ununquadium

Ununpentium, Ununhexium

Lanthanoids

Lanthanum, Cerium, Praseodymium

Neodymium, Promethium, Samarium

Europium, Gadolinium, Terbium

Dysprosium, Holmium, Erbium

Thulium, Ytterbium, Lutetium

Actinoids

Actinium, Thorium, Protactinium

Uranium, Neptunium, Plutonium

Americium, Curium, Berkelium

Californium, Einsteinium, Fermium

Mendelevium, Nobelium, Lawrencium

Page 113: Periodic Table

Metal 110

A metal is a chemical element that is a good conductor of both electricity and heat and forms cations and ionicbonds with non-metals. In chemistry, a metal (from Greek "μέταλλον" - métallon, "mine"[1] ) is an element,compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to formpositive ions (cations). Those ions are surrounded by delocalized electrons, which are responsible for theconductivity. The solid thus produced is held by electrostatic interactions between the ions and the electron cloud,which are called metallic bonds.[2]

Usage in astronomy is quite different.

DefinitionMetals are sometimes described as an arrangement of positive ions surrounded by a sea of delocalized electrons.They are one of the three groups of elements as distinguished by their ionization and bonding properties, along withthe metalloids and non-metals.Metals occupy the bulk of the periodic table, while non-metallic elements can only be found on the right-hand-sideof the Periodic Table of the Elements. A diagonal line drawn from boron (B) to polonium (Po) separates the metalsfrom the nonmetals. Most elements on this line are metalloids, sometimes called semiconductors. This is becausethese elements exhibit electrical properties common to both conductors and insulators. Elements to the lower left ofthis division line are called metals, while elements to the upper right of the division line are called non-metals.An alternative definition of metal refers to the band theory. If one fills the energy bands of a material with availableelectrons and ends up with a top band partly filled then the material is a metal. This definition opens up the categoryfor metallic polymers and other organic metals, which have been made by researchers and employed in high-techdevices. These synthetic materials often have the characteristic silvery gray reflectiveness (luster) of elementalmetals.

AstronomyIn the specialized usage of astronomy and astrophysics, the term "metal" is often used to refer collectively to allelements other than hydrogen or helium, including substances as chemically non-metallic as neon, fluorine, andoxygen. Nearly all the hydrogen and helium in the Universe was created in Big Bang nucleosynthesis, whereas allthe "metals" were produced by nucleosynthesis in stars or supernovae. The Sun and the Milky Way Galaxy arecomposed of roughly 74% hydrogen, 24% helium, and 2% "metals" (the rest of the elements; atomic numbers 3-118)by mass.[3]

The concept of a metal in the usual chemical sense is irrelevant in stars, as the chemical bonds that give elementstheir properties cannot exist at stellar temperatures.

Properties

ChemicalMetals are usually inclined to form cations through electron loss,[2] reacting with oxygen in the air to form oxidesover changing timescales (iron rusts over years, while potassium burns in seconds). Examples:

4 Na + O2 → 2 Na2O (sodium oxide)2 Ca + O2 → 2 CaO (calcium oxide)4 Al + 3 O2 → 2 Al2O3 (aluminium oxide)

The transition metals (such as iron, copper, zinc, and nickel) take much longer to oxidize. Others, like palladium, platinum and gold, do not react with the atmosphere at all. Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good

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Metal 111

conductivity for many decades (like aluminium, magnesium, some steels, and titanium). The oxides of metals aregenerally basic, as opposed to those of nonmetals, which are acidic.Painting, anodizing or plating metals are good ways to prevent their corrosion. However, a more reactive metal in theelectrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water andthe two metals form an electrochemical cell, and if the coating is less reactive than the coatee, the coating actuallypromotes corrosion.

Physical

Gallium crystals

Metals in general have high electrical conductivity, thermalconductivity, luster and density, and the ability to be deformed understress without cleaving.[2] While there are several metals that have lowdensity, hardness, and melting points, these (the alkali and alkalineearth metals) are extremely reactive, and are rarely encountered in theirelemental, metallic form. Optically speaking, metals are opaque, shinyand lustrous. This is because visible lightwaves are not readilytransmitted through the bulk of their microstructure. The large numberof free electrons in any typical metallic solid (element or alloy) isresponsible for the fact that they can never be categorized astransparent materials.

The majority of metals have higher densities than the majority of nonmetals.[2] Nonetheless, there is wide variationin the densities of metals; lithium is the least dense solid element and osmium is the densest. The metals of groups IA and II A are referred to as the light metals because they are exceptions to this generalization[2] . The high densityof most metals is due to the tightly packed crystal lattice of the metallic structure. The strength of metallic bonds fordifferent metals reaches a maximum around the center of the transition series, as those elements have large amountsof delocalized electrons in a metallic bond. However, other factors (such as atomic radius, nuclear charge, number ofbonding orbitals, overlap of orbital energies, and crystal form) are involved as well.[2]

ElectricalThe electrical and thermal conductivity of metals originate from the fact that in the metallic bond, the outer electronsof the metal atoms form a gas of nearly free electrons, moving as an electron gas in a background of positive chargeformed by the ion cores. Good mathematical predictions for electrical conductivity, as well as the electrons'contribution to the heat capacity and heat conductivity of metals can be calculated from the free electron model,which does not take the detailed structure of the ion lattice into account.When considering the exact band structure and binding energy of a metal, it is necessary to take into account thepositive potential caused by the specific arrangement of the ion cores - which is periodic in crystals. The mostimportant consequence of the periodic potential is the formation of a small band gap at the boundary of the Brillouinzone. Mathematically, the potential of the ion cores can be treated by various models, the simplest being the nearlyfree electron model.

MechanicalMechanical properties of metals include ductility, which is largely due to their inherent capacity for plasticdeformation. Reversible elasticity in metals can be described by Hooke's Law for restoring forces, where the stress islinearly proportional to the strain. Forces larger than the elastic limit, or heat, may cause a permanent (irreversible)deformation of the object, known as plastic deformation or plasticity. This irreversible change in atomic arrangementmay occur as a result of:

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• The action of an applied force (or work). An applied force may be tensile (pulling) force, compressive (pushing)force, shear, bending or torsion (twisting) forces.

• A change in temperature (or heat). A temperature change may affect the mobility of the structural defects such asgrain boundaries, point vacancies, line and screw dislocations, stacking faults and twins in both crystalline andnon-crystalline solids. The movement or displacement of such mobile defects is thermally activated, and thuslimited by the rate of atomic diffusion.

Hot metal work from a blacksmith.

Viscous flow near grain boundaries, forexample, can give rise to internal slip, creepand fatigue in metals. It can also contributeto significant changes in the microstructurelike grain growth and localized densificationdue to the elimination of intergranularporosity. Screw dislocations may slip in thedirection of any lattice plane containing thedislocation, while the principal driving forcefor "dislocation climb" is the movement ordiffusion of vacancies through a crystallattice.

In addition, the nondirectional nature ofmetallic bonding is also thought tocontribute significantly to the ductility ofmost metallic solids. When the planes of an ionic bond slide past one another, the resultant change in location shiftsions of the same charge into close proximity, resulting in the cleavage of the crystal; such shift is not observed incovalently bonded crystals where fracture and crystal fragmentation occurs.[4]

AlloysAn alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most puremetals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals asalloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys isgenerally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Of all themetallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steel) make up thelargest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low,mid and high carbon steels, with increasing carbon levels reducing ductility and toughness. The addition of siliconwill produce cast irons, while the addition of chromium, nickel and molybdenum to carbon steels (more than 10%)results in stainless steels.Other significant metallic alloys are those of aluminium, titanium, copper and magnesium. Copper alloys have beenknown since prehistory—bronze gave the Bronze Age its name—and have many applications today, mostimportantly in electrical wiring. The alloys of the other three metals have been developed relatively recently; due totheir chemical reactivity they require electrolytic extraction processes. The alloys of aluminium, titanium andmagnesium are valued for their high strength-to-weight ratios; magnesium can also provide electromagneticshielding. These materials are ideal for situations where high strength-to-weight ratio is more important than materialcost, such as in aerospace and some automotive applications.Alloys specially designed for highly demanding applications, such as jet engines, may contain more than tenelements.

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Categories

Base metalIn chemistry, the term base metal is used informally to refer to a metal that oxidizes or corrodes relatively easily, andreacts variably with dilute hydrochloric acid (HCl) to form hydrogen. Examples include iron, nickel, lead and zinc.Copper is considered a base metal as it oxidizes relatively easily, although it does not react with HCl. It is commonlyused in opposition to noble metal.In alchemy, a base metal was a common and inexpensive metal, as opposed to precious metals, mainly gold andsilver. A longtime goal of the alchemists was the transmutation of base metals into precious metals.In numismatics, coins used to derive their value primarily from the precious metal content. Most modern currenciesare fiat currency, allowing the coins to be made of base metal.

Ferrous metalThe term "ferrous" is derived from the Latin word meaning "containing iron". This can include pure iron, such aswrought iron, or an alloy such as steel. Ferrous metals are often magnetic, but not exclusively.

Noble metalNoble metals are metals that are resistant to corrosion or oxidation, unlike most base metals. They tend to beprecious metals, often due to perceived rarity. Examples include tantalum, gold, platinum, silver and rhodium.

Precious metal

A gold nugget

A precious metal is a rare metallic chemical element of high economicvalue.

Chemically, the precious metals are less reactive than most elements,have high luster and high electrical conductivity. Historically, preciousmetals were important as currency, but are now regarded mainly asinvestment and industrial commodities. Gold, silver, platinum andpalladium each have an ISO 4217 currency code. The best-knownprecious metals are gold and silver. While both have industrial uses,they are better known for their uses in art, jewelry, and coinage. Otherprecious metals include the platinum group metals: ruthenium,

rhodium, palladium, osmium, iridium, and platinum, of which platinum is the most widely traded. Plutonium anduranium could also be considered precious metals.

The demand for precious metals is driven not only by their practical use, but also by their role as investments and astore of value. Palladium was, as of summer 2006, valued at a little under half the price of gold, and platinum ataround twice that of gold. Silver is substantially less expensive than these metals, but is often traditionallyconsidered a precious metal for its role in coinage and jewelry.

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ExtractionMetals are often extracted from the Earth by means of mining, resulting in ores that are relatively rich sources of therequisite elements. Ore is located by prospecting techniques, followed by the exploration and examination ofdeposits. Mineral sources are generally divided into surface mines, which are mined by excavation using heavyequipment, and subsurface mines.Once the ore is mined, the metals must be extracted, usually by chemical or electrolytic reduction. Pyrometallurgyuses high temperatures to convert ore into raw metals, while hydrometallurgy employs aqueous chemistry for thesame purpose. The methods used depend on the metal and their contaminants.When a metal ore is an ionic compound of that metal and a non-metal, the ore must usually be smelted — heatedwith a reducing agent — to extract the pure metal. Many common metals, such as iron, are smelted using carbon as areducing agent. Some metals, such as aluminium and sodium, have no commercially practical reducing agent, andare extracted using electrolysis instead.[5]

Sulfide ores are not reduced directly to the metal but are roasted in air to convert them to oxides.

MetallurgyMetallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements,their intermetallic compounds, and their mixtures, which are called alloys.

ApplicationsSome metals and metal alloys possess high structural strength per unit mass, making them useful materials forcarrying large loads or resisting impact damage. Metal alloys can be engineered to have high resistance to shear,torque and deformation. However the same metal can also be vulnerable to fatigue damage through repeated use orfrom sudden stress failure when a load capacity is exceeded. The strength and resilience of metals has led to theirfrequent use in high-rise building and bridge construction, as well as most vehicles, many appliances, tools, pipes,non-illuminated signs and railroad tracks.The two most commonly used structural metals, iron and aluminium, are also the most abundant metals in the Earth'scrust.[6]

Metals are good conductors, making them valuable in electrical appliances and for carrying an electric current over adistance with little energy lost. Electrical power grids rely on metal cables to distribute electricity. Home electricalsystems, for the most part, are wired with copper wire for its good conducting properties.The thermal conductivity of metal is useful for containers to heat materials over a flame. Metal is also used for heatsinks to protect sensitive equipment from overheating.The high reflectivity of some metals is important in the construction of mirrors, including precision astronomicalinstruments. This last property can also make metallic jewelry aesthetically appealing.Some metals have specialized uses; radioactive metals such as uranium and plutonium are used in nuclear powerplants to produce energy via nuclear fission. Mercury is a liquid at room temperature and is used in switches tocomplete a circuit when it flows over the switch contacts. Shape memory alloy is used for applications such as pipes,fasteners and vascular stents.

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Trade

Metal and ore imports in 2005

The World Bank reports that China was the top importer of ores andmetals in 2005 followed by the U.S.A. and Japan.[7]

See also

• Amorphous metal• ASM International (society)• Ductility• Electric field screening• Metal theft• Metalworking• Periodic table (metals and non-metals)• Properties and uses of metals• Solid• Steel• Structural steel• Transition metal

External links• Martindale's 'The Reference Desk' - International Art, Business, Science & Technology [8]

References[1] μέταλλον (http:/ / www. perseus. tufts. edu/ hopper/ text?doc=Perseus:text:1999. 04. 0057:entry=me/ tallon), Henry George Liddell, Robert

Scott, A Greek-English Lexicon, on Perseus Digital Library[2] Mortimer, Charles E. (1975). Chemistry: A Conceptual Approach (3rd ed.). New York:: D. Van Nostrad Company.[3] Sparke, Linda S.; Gallagher, John S. (2000). Galaxies in the Universe (1 ed.). Cambridge University Press. p. 8. ISBN 0521592410.[4] Ductility - strength of materials (http:/ / www. engineersedge. com/ material_science/ ductility. htm)[5] "Los Alamos National Laboratory – Sodium" (http:/ / periodic. lanl. gov/ elements/ 11. html). . Retrieved 2007-06-08.[6] Frank Kreith and Yogi Goswami, eds. (2004). The CRC Handbook of Mechanical Engineering, 2nd edition. Boca Raton. p. 12-2.[7] Structure of merchandise imports (http:/ / siteresources. worldbank. org/ DATASTATISTICS/ Resources/ table4_5. pdf)[8] http:/ / www. martindalecenter. com/ GradMaterial_4_MA. html

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Metalloid 116

Metalloid

13 14 15 16 17

2 BBoron

CCarbon

NNitrogen

OOxygen

FFluorine

3 AlAluminium

SiSilicon

PPhosphorus

SSulfur

ClChlorine

4 GaGallium

GeGermanium

AsArsenic

SeSelenium

BrBromine

5 InIndium

SnTin

SbAntimony

TeTellurium

IIodine

6 TlThallium

PbLead

BiBismuth

PoPolonium

AtAstatine

Metalloid, or semi metal, is a term used in chemistry when classifying the chemical elements. On the basis of theirgeneral physical and chemical properties, nearly every element in the periodic table can be termed either a metal or anonmetal. However, a few elements with intermediate properties are referred to as metalloids (from the Greekmetallon = "metal" and eidos = "sort"). The line that separates metalloids from nonmetals in the periodic table isreferred to as the "amphoteric line".There is no rigorous definition of the term, but the following properties are usually considered characteristic ofmetalloids:• metalloids often form amphoteric oxides.• metalloids often behave as semiconductors (B, Si, Ge).The concepts of metalloid and semiconductor should not be confused. Metalloid refers to the properties of certainelements in relation to the periodic table. Semiconductor refers to the physical properties of materials (includingalloys, compounds) and there is only partial overlap between the two.The following elements are generally considered metalloids:[1] [2]

• Boron (B)• Silicon (Si)• Germanium (Ge)[3] [4]

• Arsenic (As)[5]

• Antimony (Sb)[5]

• Tellurium (Te)[5] [6]

• Polonium (Po)[7] [8]

Some allotropes of elements exhibit more pronounced metal, metalloid or non-metal behavior than others. Forexample, for the element carbon, its diamond allotrope is clearly non-metallic, but the graphite allotrope displayslimited electric conductivity more characteristic of a metalloid. Phosphorus, tin, and bismuth also have allotropesthat display borderline behavior.In the standard layout of the periodic table, metalloids occur along the diagonal line through the p block from boronto astatine. Elements to the upper right of this line display increasing nonmetallic behaviour; elements to the lowerleft display increasing metallic behaviour. This line is called the "stair-step" or "staircase." The poor metals are to theleft and down and the nonmetals are to the right and up.

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Metalloid 117

References[1] E. Sherman and G.J. Weston (1966). Chemistry of the non-metallic elements. Pergamon Press, New York. p. 64.[2] Boylan, P.J. (1962). Elements of Chemistry. Allyn and Bacon, Boston. p. 493.[3] Liu, E (1978). "Fluorination of dimethylmercury, tetramethylsilane and tetramethylgermanium. Synthesis and characterization of

polyfluorotetramethylsilanes, polyfluorotetramethylgermanes,bis(trifluoromethyl)mercury and tetrakis(trifluoromethyl)germanium". Journalof Organometallic Chemistry 145: 167. doi:10.1016/S0022-328X(00)91121-5.

[4] Schnepf, Andreas (2008). "Metalloid Cluster Compounds of Germanium: Synthesis – Properties – Subsequent Reactions". European Journalof Inorganic Chemistry 2008: 1007. doi:10.1002/ejic.200700969.

[5] Casiot, C (2002). "Optimization of the hyphenation between capillary zone electrophoresis and inductively coupled plasma massspectrometry for the measurement of As-, Sb-, Se- and Te-species, applicable to soil extracts". Spectrochimica Acta Part B AtomicSpectroscopy 57: 173. doi:10.1016/S0584-8547(01)00365-2.

[6] Chasteen, Thomas G.; Bentley, R (2003). "Biomethylation of Selenium and Tellurium: Microorganisms and Plants". Chemical Reviews 103(1): 1. doi:10.1021/cr010210. PMID 12517179.

[7] Polonium-210 Information Sheet (http:/ / www. hps. org/ documents/ po210_information_sheet. pdf)[8] Rubin, K (1997). "Degassing of metals and metalloids from erupting seamount and mid-ocean ridge volcanoes: Observations and

predictions". Geochimica et Cosmochimica Acta 61: 3525. doi:10.1016/S0016-7037(97)00179-8.

Noble gas

Group → 18

↓ Period

1 2He

2 10Ne

3 18Ar

4 36Kr

5 54Xe

6 86Rn

7 118Uuo

Legend

Noble gas

Gas

Primordial element

From decay

Synthetic

The noble gases are a group of chemical elements with very similar properties: under standard conditions, they areall odorless, colorless, monatomic gases, with very low chemical reactivity. The six noble gases that occur naturallyare helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn).

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Noble gas 118

For the first six periods of the periodic table, the noble gases are exactly the members of group 18 of the periodictable. However, this no longer holds in the seventh period (due to relativistic effects): the next member of group 18,ununoctium, is probably not a noble gas.[1] Instead, group 14 member ununquadium exhibits noble-gas-likeproperties.[2]

The properties of the noble gases can be well explained by modern theories of atomic structure: their outer shell ofvalence electrons is considered to be "full", giving them little tendency to participate in chemical reactions, and it hasonly been possible to prepare a few hundred noble gas compounds. The melting and boiling points for each noblegas are close together, differing by less than 10 °C (18 °F); consequently, they are liquids over only a smalltemperature range.Neon, argon, krypton, and xenon are obtained from air using the methods of liquefaction of gases and fractionaldistillation. Helium is typically separated from natural gas, and radon is usually isolated from the radioactive decayof dissolved radium compounds. Noble gases have several important applications in industries such as lighting,welding, and space exploration. A helium-oxygen breathing gas is often used by deep-sea divers at depths ofseawater over 180 feet (55 m) to keep the diver from experiencing oxygen toxemia, the lethal effect of high-pressureoxygen, and nitrogen narcosis, the distracting narcotic effect of the nitrogen in air beyond this partial-pressurethreshold. After the risks caused by the flammability of hydrogen became apparent, it was replaced with helium inblimps and balloons.

HistoryNoble gas is translated from the German noun Edelgas, first used in 1898 by Hugo Erdmann[3] to indicate theirextremely low level of reactivity. The name makes an analogy to the term "noble metals", which also have lowreactivity. The noble gases have also been referred to as inert gases, but this label is now deprecated as many noblegas compounds are now known.[4] Rare gases is another term that was used,[5] but this is also inaccurate becauseargon forms a fairly considerable part (0.94% by volume, 1.3% by mass) of the Earth's atmosphere.[6]

Helium was first detected in the Sun due to its characteristic spectral lines.

Pierre Janssen and Joseph Norman Lockyerdiscovered a new element on August 18,1868 while looking at the chromosphere ofthe Sun, and named it helium after theGreek word for the Sun, ήλιος (ílios orhelios).[7] No chemical analysis waspossible at the time, but helium was laterfound to be a noble gas. Before them, in

1784, the English chemist and physicist Henry Cavendish had discovered that air contains a small proportion of asubstance less reactive than nitrogen.[8] A century later, in 1895, Lord Rayleigh discovered that samples of nitrogenfrom the air were of a different density than nitrogen resulting from chemical reactions. Along with scientist WilliamRamsay at University College, London, Lord Rayleigh theorized that the nitrogen extracted from air was mixed withanother gas, leading to an experiment that successfully isolated a new element, argon, from the Greek word αργός(argós, "inactive").[8] With this discovery, they realized an entire class of gases was missing from the periodic table.During his search for argon, Ramsay also managed to isolate helium for the first time while heating cleveite, amineral. In 1902, having accepted the evidence for the elements helium and argon, Dmitri Mendeleev included thesenoble gases as group 0 in his arrangement of the elements, which would later become the periodic table.[9]

Ramsay continued to search for these gases using the method of fractional distillation to separate liquid air into several components. In 1898, he discovered the elements krypton, neon, and xenon, and named them after the Greek words κρυπτός (kryptós, "hidden"), νέος (néos, "new"), and ξένος (xénos, "stranger"), respectively. Radon was first identified in 1898 by Friedrich Ernst Dorn,[10] and was named radium emanation, but was not considered a noble gas until 1904 when its characteristics were found to be similar to those of other noble gases.[11] Rayleigh and Ramsay

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Noble gas 119

received the 1904 Nobel Prizes in Physics and in Chemistry, respectively, for their discovery of the noble gases;[12]

[13] in the words of J. E. Cederblom, then president of the Royal Swedish Academy of Sciences, "the discovery of anentirely new group of elements, of which no single representative had been known with any certainty, is somethingutterly unique in the history of chemistry, being intrinsically an advance in science of peculiar significance".[13]

The discovery of the noble gases aided in the development of a general understanding of atomic structure. In 1895,French chemist Henri Moissan attempted to form a reaction between fluorine, the most electronegative element, andargon, one of the noble gases, but failed. Scientists were unable to prepare compounds of argon until the end of the20th century, but these attempts helped to develop new theories of atomic structure. Learning from theseexperiments, Danish physicist Niels Bohr proposed in 1913 that the electrons in atoms are arranged in shellssurrounding the nucleus, and that for all noble gases except helium the outermost shell always contains eightelectrons.[11] In 1916, Gilbert N. Lewis formulated the octet rule, which concluded an octet of electrons in the outershell was the most stable arrangement for any atom; this arrangement caused them to be unreactive with otherelements since they did not require any more electrons to complete their outer shell.[14]

In 1962 Neil Bartlett discovered the first chemical compound of a noble gas, xenon hexafluoroplatinate.[15]

Compounds of other noble gases were discovered soon after: in 1962 for radon, radon fluoride,[16] and in 1963 forkrypton, krypton difluoride (KrF2).[17] The first stable compound of argon was reported in 2000 when argonfluorohydride (HArF) was formed at a temperature of 40 K (−233.2 °C; −387.7 °F).[18]

In December 1998, scientists at the Joint Institute for Nuclear Research working in Dubna, Russia bombardedplutonium (Pu) with calcium (Ca) to produce a single atom of element 114,[19] , ununquadium (Uuq).[20] Preliminarychemistry experiments have indicated this element may be the first superheavy element to show abnormalnoble-gas-like properties, even though it is a member of group 14 on the periodic table.[21] In October 2006,scientists from the Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory successfullycreated synthetically ununoctium (Uuo), the seventh element in group 18,[22] by bombarding californium (Cf) withcalcium (Ca).[23]

Chemical properties

Neon, like all noble gases, has a full valenceshell. Noble gases have eight electrons in theoutermost shell, except in the case of helium,

which has two.

The noble gases are colorless, odorless, tasteless, and nonflammableunder standard conditions. They were once labeled group 0 in theperiodic table because it was believed they had a valence of zero,meaning their atoms cannot combine with those of other elements toform compounds. However, it was later discovered some do indeedform compounds, causing this label to fall into disuse.[11]

Like other groups, the members of this family show patterns in itselectron configuration, especially the outermost shells resulting intrends in chemical behavior:

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Noble gas 120

Z Element No. of electrons/shell

2 helium 2

10 neon 2, 8

18 argon 2, 8, 8

36 krypton 2, 8, 18, 8

54 xenon 2, 8, 18, 18, 8

86 radon 2, 8, 18, 32, 18, 8

The noble gases have full valence electron shells. Valence electrons are the outermost electrons of an atom and arenormally the only electrons that participate in chemical bonding. Atoms with full valence electron shells areextremely stable and therefore do not tend to form chemical bonds and have little tendency to gain or loseelectrons.[24] However, heavier noble gases such as radon are held less firmly together by electromagnetic force thanlighter noble gases such as helium, making it easier to remove outer electrons from heavy noble gases.As a result of a full shell, the noble gases can be used in conjunction with the electron configuration notation to formthe noble gas notation. To do this, the nearest noble gas that precedes the element in question is written first, andthen the electron configuration is continued from that point forward. For example, the electron notation of carbon is1s²2s²2p², and the noble gas notation is [He]2s²2p². This notation makes it easier to identify elements, and is shorterthan writing out the full notation of atomic orbitals.[25]

Compounds

Structure of XeF4, one of the first noble gascompounds to be discovered.

The noble gases show extremely low chemical reactivity;consequently, only a few hundred noble gas compounds have beenformed. Neutral compounds in which helium and neon are involved inchemical bonds have not been formed (although there is sometheoretical evidence for a few helium compounds), while xenon,krypton, and argon have shown only minor reactivity.[26] The reactivityfollows the order Ne < He < Ar < Kr < Xe < Rn.

In 1933, Linus Pauling predicted that the heavier noble gases couldform compounds with fluorine and oxygen. He predicted the existenceof krypton hexafluoride (KrF6) and xenon hexafluoride (XeF6),speculated XeF8 might exist as an unstable compound, and suggestedxenic acid could form perxenate salts.[27] [28] These predictions were

shown to be generally accurate, except XeF8 is now thought to be both thermodynamically and kineticallyunstable.[29]

Xenon compounds are the most numerous of the noble gas compounds that have been formed.[30] Most of them havethe xenon atom in the oxidation state of +2, +4, +6, or +8 bonded to highly electronegative atoms such as fluorine oroxygen, as in xenon difluoride (XeF2), xenon tetrafluoride (XeF4), xenon hexafluoride (XeF6), xenon tetroxide(XeO4), and sodium perxenate (Na4XeO6). Some of these compounds have found use in chemical synthesis asoxidizing agents; XeF2, in particular, is commercially available and can be used as a fluorinating agent.[31] As of2007, about five hundred compounds of xenon bonded to other elements have been identified, includingorganoxenon compounds (those bonded to carbon), and xenon bonded to nitrogen, chlorine, gold, mercury, andxenon itself.[26] [32] Compounds of xenon bound to boron, hydrogen, bromine, iodine, beryllium, sulphur, titanium,copper, and silver have also been observed but only at low temperatures in noble gas matrices, or in supersonic noblegas jets.[26]

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Noble gas 121

In theory, radon is more reactive than xenon, and therefore should form chemical bonds more easily than xenondoes. However, due to the high radioactivity and short half-life of radon isotopes, only a few fluorides and oxides ofradon have been formed in practice.[33]

Krypton is less reactive than xenon, but several compounds have been reported with krypton in the oxidation state of+2.[26] Krypton difluoride is the most notable and easily characterized. Compounds in which krypton forms a singlebond to nitrogen and oxygen have also been characterized,[34] but are only stable below −60 °C (−76 °F) and −90 °C(−130 °F) respectively).[26]

Krypton atoms chemically bound to other nonmetals (hydrogen, chlorine, carbon) as well as some late transitionmetals (copper, silver, gold) have also been observed, but only either at low temperatures in noble gas matrices, or insupersonic noble gas jets.[26] Similar conditions were used to obtain the first few compounds of argon in 2000, suchas argon fluorohydride (HArF), and some bound to the late transition metals copper, silver, and gold.[26] As of 2007,no stable neutral molecules involving covalently bound helium or neon are known.[26]

The noble gases—including helium—can form stable molecular ions in the gas phase. The simplest is the heliumhydride molecular ion, HeH+, discovered in 1925.[35] Because it is composed of the two most abundant elements inthe universe, hydrogen and helium, it is believed to occur naturally in the interstellar medium, although it has notbeen detected yet.[36] In addition to these ions, there are many known neutral excimers of the noble gases. These arecompounds such as ArF and KrF that are stable only when in an excited electronic state; some of them findapplication in excimer lasers.In addition to the compounds where a noble gas atom is involved in a covalent bond, noble gases also formnon-covalent compounds. The clathrates, first described in 1949,[37] consist of a noble gas atom trapped withincavities of crystal lattices of certain organic and inorganic substances. The essential condition for their formation isthat the guest (noble gas) atoms must be of appropriate size to fit in the cavities of the host crystal lattice. Forinstance, argon, krypton, and xenon form clathrates with hydroquinone, but helium and neon do not because they aretoo small or insufficiently polarizable to be retained.[38] Neon, argon, krypton, and xenon also form clathratehydrates, where the noble gas is trapped in ice.[39]

An endohedral fullerene compound containing anoble gas atom

Noble gases can form endohedral fullerene compounds, in which thenoble gas atom is trapped inside a fullerene molecule. In 1993, it wasdiscovered that when C60, a spherical molecule consisting of60 carbon atoms, is exposed to noble gases at high pressure, complexessuch as He@C60 can be formed (the @ notation indicates He iscontained inside C60 but not covalently bound to it).[40] As of 2008,endohedral complexes with helium, neon, argon, krypton, and xenonhave been obtained.[41] These compounds have found use in the studyof the structure and reactivity of fullerenes by means of the nuclearmagnetic resonance of the noble gas atom.[42]

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Noble gas 122

Bonding in XeF2 according to the 3-center-4-electron bond model

Noble gas compounds such as xenondifluoride (XeF2) are considered to behypervalent because they violate the octetrule. Bonding in such compounds can beexplained using a 3-center-4-electron bondmodel.[43] [44] This model, first proposed in1951, considers bonding of three collinearatoms. For example, bonding in XeF2 isdescribed by a set of three molecularorbitals (MOs) derived from p-orbitals oneach atom. Bonding results from the

combination of a filled p-orbital from Xe with one half-filled p-orbital from each F atom, resulting in a filledbonding orbital, a filled non-bonding orbital, and an empty antibonding orbital. The highest occupied molecularorbital is localized on the two terminal atoms. This represents a localization of charge which is facilitated by the highelectronegativity of fluorine.[45]

The chemistry of heavier noble gases, krypton and xenon, are well established. The chemistry of the lighter ones,argon and helium, is still at an early stage, while a neon compound is still yet to be identified.

Occurrence and productionThe abundances of the noble gases in the universe decrease as their atomic numbers increase. Helium is the mostcommon element in the universe after hydrogen, with a mass fraction of about 24%. Most of the helium in theuniverse was formed during Big Bang nucleosynthesis, but the amount of helium is steadily increasing due to thefusion of hydrogen in stellar nucleosynthesis.[46] [47] Abundances on Earth follow different trends; for example,helium is only the third most abundant noble gas in the atmosphere. The reason is that there is no primordial heliumin the atmosphere; due to the small mass of the atom, helium cannot be retained by the Earth's gravitational field.[48]

Helium on Earth comes from the alpha decay of heavy elements such as uranium and thorium found in the Earth'scrust, and tends to accumulate in natural gas deposits.[48] The abundance of argon, on the other hand, is increased asa result of the beta decay of potassium-40, also found in the Earth's crust, to form argon-40, which is the mostabundant isotope of argon on Earth despite being relatively rare in the Solar System. This process is the base for thepotassium-argon dating method.[49] Xenon has an unexpectedly low abundance in the atmosphere, in what has beencalled the missing xenon problem; one theory is that the missing xenon may be trapped in minerals inside the Earth'scrust.[50] Radon is formed in the lithosphere as from the alpha decay of radium. It can seep into buildings throughcracks in their foundation and accumulate in areas that are not well ventilated. Due to its high radioactivity, radonpresents a significant health hazard; it is implicated in an estimated 21,000 lung cancer deaths per year in the UnitedStates alone.[51]

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Noble gas 123

Abundance Helium Neon Argon Krypton Xenon Radon

Solar System (for each atom of silicon)[52] 2343 2.148 0.1025 5.515 × 10−5 5.391 × 10−6 –

Earth's atmosphere (volume fraction inppm)[53]

5.20 18.20 9340.00 1.10 0.09 (0.06–18) × 10−19[54]

Igneous rock (mass fraction in ppm)[55] 3 × 10−3 7 × 10−5 4 × 10−2 – – 1.7 × 10−10

Gas 2004 price(USD/m3)

[56]

Helium (industrial grade) 4.20–4.90

Helium (laboratory grade) 22.30–44.90

Argon 2.70–8.50

Neon 60–120

Krypton 400–500

Xenon 4000–5000

Neon, argon, krypton, and xenon are obtained from air using the methods of liquefaction of gases, to convertelements to a liquid state, and fractional distillation, to separate mixtures into component parts. Helium is typicallyproduced by separating it from natural gas, and radon is isolated from the radioactive decay of radiumcompounds.[11] The prices of the noble gases are influenced by their natural abundance, with argon being thecheapest and xenon the most expensive. As an example, the table to the right lists the 2004 prices in the UnitedStates for laboratory quantities of each gas.

Applications

Liquid helium is used to cool the superconductingmagnets in modern MRI scanners.

Noble gases have very low boiling and melting points, which makesthem useful as cryogenic refrigerants.[57] In particular, liquid helium,which boils at 4.2 K (−268.95 °C; −452.11 °F), is used forsuperconducting magnets, such as those needed in nuclear magneticresonance imaging and nuclear magnetic resonance.[58] Liquid neon,although it does not reach temperatures as low as liquid helium, alsofinds use in cryogenics because it has over 40 times more refrigeratingcapacity than liquid helium and over three times more than liquidhydrogen.[54]

Helium is used as a component of breathing gases to replace nitrogen,due its low solubility in fluids, especially in lipids. Gases are absorbed

by the blood and body tissues when under pressure like in scuba diving, which causes an anesthetic effect known asnitrogen narcosis.[59] Due to its reduced solubility, little helium is taken into cell membranes, and when helium isused to replace part of the breathing mixtures, such as in trimix or heliox, a decrease in the narcotic effect of the gasat depth is obtained.[60] Helium's reduced solubility offers further advantages for the condition known asdecompression sickness, or the bends.[11] [61] The reduced amount of dissolved gas in the body means that fewer gasbubbles form during the decrease in pressure of the ascent. Another noble gas, argon, is considered the best optionfor use as a drysuit inflation gas for scuba diving.[62]

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Noble gas 124

The Spirit of Goodyear, one of the iconicGoodyear Blimps

Since the Hindenburg disaster in 1937,[63] helium has replacedhydrogen as a lifting gas in blimps and balloons due to its lightness andincombustibility, despite an 8.6%[64] decrease in buoyancy.[11]

In many applications, the noble gases are used to provide an inertatmosphere. Argon is used in the synthesis of air-sensitive compoundsthat are sensitive to nitrogen. Solid argon is also used for the study ofvery unstable compounds, such as reactive intermediates, by trappingthem in an inert matrix at very low temperatures.[65] Helium is used asthe carrier medium in gas chromatography, as a filler gas for thermometers, and in devices for measuring radiation,such as the Geiger counter and the bubble chamber.[56] Helium and argon are both commonly used to shield weldingarcs and the surrounding base metal from the atmosphere during welding and cutting, as well as in othermetallurgical processes and in the production of silicon for the semiconductor industry.[54]

15,000-watt xenon short-arc lamp used in IMAXprojectors

Noble gases are commonly used in lighting because of their lack ofchemical reactivity. Argon, mixed with nitrogen, is used as a filler gasfor incandescent light bulbs.[54] Krypton is used in high-performancelight bulbs, which have higher color temperatures and greaterefficiency, because it reduces the rate of evaporation of the filamentmore than argon; halogen lamps, in particular, use krypton mixed withsmall amounts of compounds of iodine or bromine.[54] The noble gasesglow in distinctive colors when used inside gas-discharge lamps, suchas neon lights, which produce an orange-red color. Xenon is commonlyused in xenon arc lamps which, due to their nearly continuousspectrum that resembles daylight, find application in film projectorsand as automobile headlamps.[54]

The noble gases are used in excimer lasers, which are based on short-lived electronically excited molecules knownas excimers. The excimers used for lasers may be noble gas dimers such as Ar2, Kr2 or Xe2, or more commonly, thenoble gas is combined with a halogen in excimers such as ArF, KrF, XeF, or XeCl. These lasers produce ultravioletlight which, due to its short wavelength (193 nm for ArF and 248 nm for KrF), allows for high-precision imaging.Excimer lasers have many industrial, medical, and scientific applications. They are used for microlithography andmicrofabrication, which are essential for integrated circuit manufacture, and for laser surgery, including laserangioplasty and eye surgery.[66]

Some noble gases have direct application in medicine. Helium is sometimes used to improve the ease of breathing ofasthma sufferers.[54] Xenon is used as an anesthetic because of its high solubility in lipids, which makes it morepotent than the usual nitrous oxide, and because it is readily eliminated from the body, resulting in fasterrecovery.[67] Xenon finds application in medical imaging of the lungs through hyperpolarized MRI.[68] Radon, whichis highly radioactive and is only available in minute amounts, is used in radiotherapy.[11]

Discharge color

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Noble gas 125

Colors and spectra (bottom row) of electric discharge in pure noble gases

Helium Neon Argon(with some Hg in the "Ar" image)

Krypton Xenon

The color of gas discharge emission depends on several factors, including the following:[69]

• discharge parameters (local value of current density and electric field, temperature, etc. – note the color variationalong the discharge in the top row);

• gas purity (even small fraction of certain gases can affect color);• color balance and saturation level of the image recording medium;• material of the discarge tube envelope – note suppression of the UV and blue components in the bottom-row

tubes made of thick household glass.

See also• Noble gas (data page), for extended tables of physical properties.• Noble metal, for metals that are resistant to corrosion or oxidation.• Inert gas, for any gas that is not reactive under normal circumstances.• Industrial gas

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[40] Saunders, M.; Jiménez-Vázquez, H. A.; Cross, R. J.; Poreda, R. J. (1993). "Stable compounds of helium and neon. He@C60 and Ne@C60".Science 259 (5100): 1428–1430. doi:10.1126/science.259.5100.1428. PMID 17801275.

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[42] Frunzi, Michael; Cross, R. James; Saunders, Martin (2007). "Effect of Xenon on Fullerene Reactions". Journal of the American ChemicalSociety 129 (43): 13343. doi:10.1021/ja075568n. PMID 17924634.

[43] Greenwood 1997, p. 897[44] Weinhold 2005, pp. 275–306[45] Pimentel, G. C. (1951). "The Bonding of Trihalide and Bifluoride Ions by the Molecular Orbital Method". The Journal of Chemical Physics

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Noble metal

The noble metals including mercury and rheniumtogether with the non-noble metal copper ordered

according their position in the periodic table ofthe elements

Noble metals are metals that are resistant to corrosion and oxidation inmoist air, unlike most base metals. They tend to be precious, often dueto their rarity in the Earth's crust. The noble metals are considered to be(in order of increasing atomic number)[1] ruthenium, rhodium,palladium, silver, osmium, iridium, platinum, gold .

Other sources include mercury[2] [3] [4] or even rhenium[5] as a noblemetal. On the other hand, neither titanium nor niobium nor tantalumare called noble metals despite the fact that they are very resistant tocorrosion.

Noble metals should not be confused with precious metals (althoughmany noble metals are precious).

IntroductionPalladium, osmium, platinum, gold and mercury can be dissolved in aqua regia, a highly concentrated mixture ofhydrochloric acid and nitric acid, but iridium and silver cannot. (Silver can dissolve in nitric acid though.)Ruthenium can be dissolved in aqua regia only when in the presence of oxygen, while rhodium must be in a finepulverized form. Niobium and tantalum are resistant to acids, including aqua regia. [6]

This term can also be used in a relative sense, considering "noble" as an adjective for the word "metal". A "galvanicseries" is a hierarchy of metals (or other electrically conductive materials, including composites and semimetals) thatruns from noble to active, and allows designers to see at a glance how materials will interact in the environment usedto generate the series. In this sense of the word, graphite is more noble than silver and the relative nobility of manymaterials is highly dependent upon context, as for aluminium and stainless steel in conditions of varying pH.[7]

In physics, the definition of a noble metal is even more strict. It is required that the d-bands of the electronicstructure are filled. Taking this into account, only copper, silver and gold are noble metals, as all d-like band arefilled and don't cross the Fermi level.[8] For platinum two d-bands cross the Fermi level, changing its chemicalbehaviour; it is used as a catalyst. The different reactivity can easily be seen while preparing clean metal surfaces inultra high vacuum; surfaces of "physical defined" noble metals (e.g., gold) are easy to clean and stay clean for a longtime, while those of platinum or palladium, for example, are covered by carbon monoxide very quickly.[9]

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Noble metal 129

ElectrochemistryMetallic elements, including several non-noble metals, sorted by their chemical "nobility" (noble metals bolded): [10]

element group reaction potential

Gold Ib/6 Au → Au3+ + 3 e− 1.498 V

Platinum VIIIb/6 Pt → Pt2+ + 2 e− 1.18 V

Iridium VIIIb/6 Ir → Ir3+ + 3 e− 1.156 V

Palladium VIIIb/5 Pd → Pd2+ + 2 e− 0.987 V

Osmium VIIIb/6 Os + 4 H2O → OsO4 + 8 H+ + 8 e− 0.838 V

Silver Ib/5 Ag → Ag+ + e− 0.7996 V

Mercury IIb/6 2 Hg → Hg22+ + 2 e− 0.7973 V

Polonium VIa/6 Po → Po2+ + 2 e− 0.65 V[11]

Rhodium VIIIb/5 Rh → Rh2+ + 2 e− 0.600 V

Ruthenium VIIIb/5 Ru → Ru2+ + 2 e− 0.455 V

Copper Ib/4 Cu → Cu2+ + 2 e− 0.337 V

Bismuth Va/6 Bi → Bi3+ + 3 e− 0.308 V

Technetium VIIb/5 Tc + 2 H2O → TcO2 + 4 H+ + 4 e− 0.272 V

Rhenium VIIb/6 Re + 2 H2O → ReO2 + 4 H+ + 4 e− 0.259 V

Antimony Va/5 2 Sb + 3 H2O → Sb2O3 + 6 H+ + 6 e− 0.152 V

The column group denotes its position in the periodic table, hence electronic configuration. The simplified reactions,listed in the next column, can also be read in detail from the Pourbaix diagrams of the considered element in water.Finally the column potential indicates the electric potential of the element measured against a H-electrode inaqueous, pH 7 solution. All missing elements in this table are either not metals or have a negative standard potential.Antimony and polonium are considered metalloids and thus can not be noble metals. Also chemists and metallurgistsconsider copper and bismuth not noble metals because they easily oxidize due to the reaction O2 + 2 H2O + 4 e− ⇄ 4OH−(aq) +0.40 V which is possible in moist air.Silver and copper film over and oxidize easily and readily, thus the copper sheets with a patina of oxidation used inarchitectural designs and the resultant market for a myriad of silver polishing compounds. The film over of Silver isdue to its high sensibility to hydrogen sulfide. Chemically patina is caused by an attack of oxygen in wet air and byCO2 afterward.[6] On the other hand, rhenium coated mirrors are said to be very durable,[6] despite the fact thatrhenium and technetium are said to tarnish slowly in moist atmosphere.[12]

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Noble metal 130

See also• Base metal• Precious metal

References[1] A. Holleman, N. Wiberg, "Lehrbuch der Anorganischen Chemie", de Gruyter, 1985, 33. edition, p. 1486[2] Die Adresse für Ausbildung, Studium und Beruf (http:/ / www. uni-protokolle. de/ Lexikon/ Edelmetall. html)[3] "Dictionary of Mining, Mineral, and Related Terms", Compiled by the American Geological Institute, 2nd edition, 1997[4] Scoullos, M.J., Vonkeman, G.H., Thornton, I., Makuch, Z., "Mercury - Cadmium - Lead: Handbook for Sustainable Heavy Metals Policy and

Regulation",Series: Environment & Policy, Vol. 31, Springer-Verlag, 2002[5] The New Encyclopedia Britannica, 15th edition, Vol. VII, 1976[6] A. Holleman, N. Wiberg, "Inorganic Chemistry", Academic Press, 2001[7] Everett Collier, "The Boatowner’s Guide to Corrosion", International Marine Publishing, 2001, p. 21[8] Hüger, E.; Osuch, K. (2005). "Making a noble metal of Pd". EPL (Europhysics Letters) 71: 276. doi:10.1209/epl/i2005-10075-5.[9] S. Fuchs, T.Hahn, H.G. Lintz, "The oxidation of carbon monoxide by oxygen over platinum, palladium and rhodium catalysts from 10−10 to 1

bar", Chemical engineering and processing, 1994, V 33(5), pp. 363-369 (http:/ / cat. inist. fr/ ?aModele=afficheN& cpsidt=3322977)[10] D. R. Lidle editor, "CRC Handbook of Chemistry and Physics", 86th edition, 2005[11] A. J. Bard, "Encyclopedia of the Electrochemistry of the Elements", Vol. IV, Marcel Dekker Inc., 1975[12] R. D. Peack, "The Chemistry of Technetium and Rhenium", Elsevier, 1966

Notes• R. R. Brooks, "Noble metals and biological systems: their role in Medicine, Mineral Exploration, and the

Environment", CRC Press, 1992

External links• noble metal - chemistry (http:/ / www. britannica. com/ EBchecked/ topic/ 416979/ noble-metal) Encyclopædia

Britannica, online edition• To see which bands cross the Fermi level, the Fermi surfaces of almost all the metals can be found at the Fermi

Surface Database (http:/ / www. phys. ufl. edu/ fermisurface/ )• The following article might also clarify the correlation between band structure and the term noble metal: Hüger,

E.; Osuch, K. (2005). "Making a noble metal of Pd". EPL (Europhysics Letters) 71: 276.doi:10.1209/epl/i2005-10075-5.

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Nonmetal 131

NonmetalNonmetal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of theirgeneral physical and chemical properties, every element in the periodic table can be termed either a metal or anonmetal. (A few elements with intermediate properties are referred to as metalloids).The elements generally regarded as nonmetals are:• hydrogen (H)• In Group 14: carbon (C)• In Group 15 (the pnictogens): nitrogen (N), phosphorus (P)• Several elements in Group 16, the chalcogens: oxygen (O), sulfur (S), selenium (Se)• All elements in Group 17 - the halogens• All elements in Group 18 - the noble gasesThere is no rigorous definition for the term "nonmetal" - it covers a general spectrum of behaviour. Commonproperties considered characteristic of a nonmetal include:• poor conductors of heat and electricity when compared to metals• they form acidic oxides (whereas metals generally form basic oxides)• in solid form, they are dull and brittle, rather than metals which are lustrous, ductile or malleable• usually have lower densities than metals• they have significantly lower melting points and boiling points than metals• non-metals have high electronegativityThey also have a negative valence, compared to the positive valence of metals.Only eighteen elements in the periodic table are generally considered nonmetals, compared to over eighty metals, butnonmetals make up most of the crust, atmosphere and oceans of the earth. Bulk tissues of living organisms arecomposed almost entirely of nonmetals. Most nonmetals are monatomic noble gases or form diatomic molecules intheir elemental state, unlike metals which (in their elemental state) do not form molecules at all.

Metallisation at huge pressuresNevertheless, even these 18 elements tend to become metallic at large enough pressures (see nearby periodic table at~300 GPa).

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Platinum group 132

Platinum group

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Cs Ba La * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac ** Rf Db Sg Bh Hs Mt Ds Rg Cn

* Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Platinum group metals

The platinum group metals (abbreviated as the PGMs; alternatively, the platinoids, platidises, platinum group orplatinum metals) sometimes collectively refers to six metallic elements clustered together in the periodic table.These elements are all transition metals, lying in the d-block (groups 8, 9, and 10, periods 5 and 6).The six platinum group metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum. They havesimilar physical and chemical properties, and tend to occur together in the same mineral deposits.[1]

HistoryNaturally occurring platinum and platinum-rich alloys have been known by pre-Columbian Americans for a longtime.[2] Though the metal was used by pre-Columbian peoples, the first European reference to platinum appears in1557 in the writings of the Italian humanist Julius Caesar Scaliger (1484–1558) as a description of a mysteriousmetal found in Central American mines between Darién (Panama) and Mexico ("up until now impossible to melt byany of the Spanish arts").[2]

The Spaniards named the metal platina ("little silver") when they first encountered it in Colombia. They regardedplatinum as an unwanted impurity in the silver they were mining.[2] [3]

PropertiesThe platinum metals have outstanding catalytic properties. They are highly resistant to wear and tarnish, makingplatinum, in particular, well suited for fine jewelry. Other distinctive properties include resistance to chemical attack,excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploitedfor industrial applications.[4]

SourcesPlatinum

Sperrylite (platinum arsenide, PtAs2) ore is a major source of this metal. A naturally occurring platinum-iridium alloy, platiniridium, is found in the mineral cooperite (platinum sulfide, PtS). Platinum in a native state, often accompanied by small amounts of other platinum metals, is found in alluvial and placer deposits in Colombia, Ontario, the Ural Mountains, and in certain western American states. Platinum is also produced commercially as a by-product of nickel ore processing. The huge quantities of nickel ore processed

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Platinum group 133

makes up for the fact that platinum makes up only two parts per million of the ore. South Africa, with vastplatinum ore deposits in the Merensky Reef of the Bushveld complex, is the world's largest producer ofplatinum, followed by Russia.[5] [6] Platinum and palladium are also mined commercially from the Stillwaterigneous complex in Montana, USA.

OsmiumIridiosmium is a naturally occurring alloy of iridium and osmium found in platinum-bearing river sands in theUral Mountains and in North and South America. Trace amounts of osmium also exist in nickel-bearing oresfound in the Sudbury, Ontario region along with other platinum group metals. Even though the quantity ofplatinum metals found in these ores is small, the large volume of nickel ores processed makes commercialrecovery possible.[6] [7]

IridiumMetallic iridium is found with platinum and other platinum group metals in alluvial deposits. Naturallyoccurring iridium alloys include osmiridium and iridiosmium, both of which are mixtures of iridium andosmium. It is recovered commercially as a by-product from nickel mining and processing.[6]

RutheniumRuthenium is generally found in ores with the other platinum group metals in the Ural Mountains and in Northand South America. Small but commercially important quantities are also found in pentlandite extracted fromSudbury, Ontario and in pyroxenite deposits in South Africa.[6]

RhodiumThe industrial extraction of rhodium is complex as the metal occurs in ores mixed with other metals such aspalladium, silver, platinum, and gold. It is found in platinum ores and obtained free as a white inert metalwhich is very difficult to fuse. Principal sources of this element are located in river sands of the UralMountains, in North and South America and also in the copper-nickel sulfide mining area of the SudburyBasin region. Although the quantity at Sudbury is very small, the large amount of nickel ore processed makesrhodium recovery cost effective. However, the annual world production in 2003 of this element is only 7 or8 tons and there are very few rhodium minerals.[8]

PalladiumPalladium is found as a free metal and alloyed with platinum and gold with platinum group metals in placerdeposits of the Ural Mountains of Eurasia, Australia, Ethiopia, South and North America. However it iscommercially produced from nickel-copper deposits found in South Africa and Ontario, Canada. The hugevolume of nickel-copper ore processed makes this extraction profitable in spite of its low concentration inthese ores.[8]

ProductionThe production of pure platinum group metals normally starts from residues of the production of other metals with amixture of several of those metals. One typical starting product is the anode residue of gold or nickel production. Thedifferences in chemical reactivity and solubility of several compounds of the metals under extraction are used toseparate them.[4]

A first step is to dissolve all the metals in aqua regia forming their respective nitrates. If silver is still present, this isthen separated by forming insoluble silver chloride. Rhodium sulfate is separated after the salts have been meltedtogether with sodium hydrogensulfate and leached with water. The residue is then melted together with sodiumperoxide, which dissolves all the metals and leaves the iridium. The two remaining metals, ruthenium and osmium,form ruthenium and osmium tetroxides after chlorine has been added to solution. The osmium tetroxide is thendissolved in alcoholic sodium hydroxide and separated from the ruthenium tetroxides. All of these metals' finalchemical compounds can ultimately be reduced to the elemental metal using hydrogen.[4]

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Platinum group 134

Production in nuclear reactorsSignificant quantities of platinum group metals – Ruthenium, Rhodium and Palladium are formed as fission productsin nuclear reactors.[9] With escalating prices and increasing global demand, reactor produced noble metals areemerging as an alternative source. Various reports are available on the possibility of recovering fission noble metalsfrom spent nuclear fuel.[10] [11] [12]

Recently there is an upsurge in the recovery of valuable fission products which reflects in the form of articles inleading scientific journals. Palladium has been of special interest due to its less complex behavior when compared torhodium and ruthenium. The special interest in palladium may be also due to its widespread application in chemicalcatalysis and the electronics industry. Several research groups are exploring the possibility of recovering palladiumby various methods like direct electrolysis of high-level liquid waste,[13] [14] using room temperature ionic liquids(RTILs) as electrolyte for nuclear fuel dissolution and recovery,[15] solvent extraction, ion exchange, etc. Roomtemperature ionic liquids have been employed to recover rhodium,[16] and ruthenium [17] also recently.

See also• Platinum group metals in Africa• Merensky Reef

External links• Platinum Today: The world's leading authority on platinum group metals [18]

• Platinum Group Spot Prices [19]

• USGS page on PGM's [20]

• Platinum Metals Review: the quarterly E-journal of research on the platinum metals and of developments in theirapplication in industry [21]

References[1] Harris, D. C.; Cabri L. J. (1991). "Nomenclature of platinum-group-element alloys; review and revision". The Canadian Mineralogist 29 (2):

231–237.[2] Weeks, M. E. (1968). Discovery of the Elements (7 ed.). Journal of Chemical Education. pp. 385–407. ISBN 0848685792. OCLC 23991202.[3] Woods, Ian (2004). The Elements: Platinum (http:/ / books. google. com/ ?id=hy2WcbKpXSkC& printsec=frontcover). Benchmark Books.

ISBN 978-0761415503. .[4] Hunt, L. B.; Lever, F. M. (1969). "Platinum Metals: A Survey of Productive Resources to industrial Uses" (http:/ / www.

platinummetalsreview. com/ pdf/ pmr-v13-i4-126-138. pdf). Platinum Metals Review 13 (4): 126–138. . Retrieved 2009-10-02.[5] Xiao, Z.; Laplante, A. R. (2004). "Characterizing and recovering the platinum group minerals—a review". Minerals Engineering 17:

961–979. doi:10.1016/j.mineng.2004.04.001.[6] "Platinum–Group Metals" (http:/ / minerals. usgs. gov/ minerals/ pubs/ commodity/ platinum/ platimcs07. pdf) (PDF). U.S. Geological

Survey, Mineral Commodity Summaries. January 2007. . Retrieved 2008-09-09.[7] Emsley, J. (2003). "Iridium" (http:/ / books. google. com/ ?id=j-Xu07p3cKwC& pg=PA202). Nature's Building Blocks: An A-Z Guide to the

Elements. Oxford, England, UK: Oxford University Press. pp. 201–204. ISBN 0198503407. .[8] Chevalier, Patrick (?). "Mineral Yearbook: Platinum Group Metals" (http:/ / www. nrcan-rncan. gc. ca/ mms-smm/ busi-indu/ cmy-amc/

content/ 2004/ 71. pdf). Natural Resources Canada. . Retrieved 2008-10-17.[9] R. J. Newman, F. J. Smith (1970). "Platinum Metals from Nuclear Fission – an evaluation of their possible use by the industry" (http:/ / www.

platinummetalsreview. com/ dynamic/ article/ view/ pmr-v14-i3-088-092). Platinum Metals Review 14 (3): 88. .[10] Zdenek Kolarik, Edouard V. Renard (2003). "Recovery of Value Fission Platinoids from Spent Nuclear Fuel; PART I: general

considerations and basic chemistry" (http:/ / www. platinummetalsreview. com/ dynamic/ article/ view/ pmr-v47-i2-074-087). PlatinumMetals Review 47 (2): 74. .

[11] Kolarik, Zdenek; Renard, Edouard V. (2005). "Potential Applications of Fission Platinoids in Industry" (http:/ / www.platinummetalsreview. com/ dynamic/ article/ view/ 49-2-79-90). Platinum Metals Review 49: 79. doi:10.1595/147106705X35263. .

[12] Zdenek Kolarik, Edouard V. Renard (2003). "Recovery of Value Fission Platinoids from Spent Nuclear Fuel; PART II: Separation process"(http:/ / www. platinummetalsreview. com/ dynamic/ article/ view/ pmr-v47-i3-123-131). Platinum Metals Review 47 (3): 123. .

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Platinum group 135

[13] Jayakumar, M; Venkatesan, K; Srinivasan, T; Rao, P (2009). "Studies on the feasibility of electrochemical recovery of palladium fromhigh-level liquid waste". Electrochimica Acta 54: 1083. doi:10.1016/j.electacta.2008.08.034.

[14] Pokhitonov, Yu. A.; Romanovskii, V. N. (2005). "Palladium in Irradiated Fuel. Are There Any Prospects for Recovery and Application?".Radiochemistry 47: 1. doi:10.1007/s11137-005-0040-7.

[15] Jayakumar, M; Venkatesan, K; Srinivasan, T (2007). "Electrochemical behavior of fission palladium in 1-butyl-3-methylimidazoliumchloride". Electrochimica Acta 52: 7121. doi:10.1016/j.electacta.2007.05.049.

[16] Jayakumar, M; Venkatesan, K; Srinivasan, T (2008). "Electrochemical behavior of rhodium(III) in 1-butyl-3-methylimidazolium chlorideionic liquid". Electrochimica Acta 53: 2794. doi:10.1016/j.electacta.2007.10.056.

[17] Jayakumar, M; Venkatesan, K.A.; Srinivasan, T.G.; Vasudeva Rao, P.R. (2008). "Electrochemical behavior of ruthenium (III), rhodium (III)and palladium (II) in 1-butyl-3-methylimidazolium chloride ionic liquid". Electrochimica Acta 54: 2747. doi:10.1016/j.electacta.2009.06.043.

[18] http:/ / www. platinum. matthey. com/[19] http:/ / www. kitco. com/ market/[20] http:/ / minerals. usgs. gov/ minerals/ pubs/ commodity/ platinum/[21] http:/ / www. platinummetalsreview. com/ dynamic/

Post-transition metal

Group # 12 13 14 15

Period

4 30Zn

31Ga

5 48Cd

49In

50Sn

6 80Hg

81Tl

82Pb

83Bi

Atomic numbers showstate at STP

Solids Liquids

In chemistry, the term post-transition metal is used to describe the category of metallic elements to the right of thetransition elements on the periodic table[1] [2] . IUPAC defines "transition elements" as either the elements in groups3–11 or the elements in groups 3–12[3] . According to the first definition, post-transition metals include group12—zinc, cadmium, and mercury. This collection of elements is illustrated by the element boxes to the right.Occasionally germanium, antimony, and/or polonium are also included as metals, although these are usuallyconsidered to be metalloids. According to the second definition of transition elements, group 12 would not beincluded as a post-transition metal. An examination of textbooks and monographs in 2003 revealed that bothdefinitions are used with roughly equal frequency[4] .In the 1950s, most inorganic chemistry textbooks defined transition elements as excluding group 11—copper, silver,and gold in addition to group 12[4] . A third definition of post-transition metal that includes group 11 and group 12elements is no longer recommended by IUPAC[3] but is still used on occasion[5] [6] .

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Post-transition metal 136

Poor metalsThe trivial name poor metals is sometimes applied to the metallic elements in the p-block of the periodic table.Their melting and boiling points are generally lower than those of the transition metals and their electronegativityhigher, and they are also softer. They are distinguished from the metalloids, however, by their significantly higherboiling points in the same row."Poor metals" is not a rigorous IUPAC-approved nomenclature, but the grouping is generally taken to includealuminium, gallium, indium, tin, thallium, lead, and bismuth. Occasionally germanium, antimony, and polonium arealso included, although these are usually considered to be metalloids or "semi-metals". Elements 113, 114, 115, and116, which are currently allocated the systematic names ununtrium, ununquadium, ununpentium, and ununhexium,would likely exhibit properties characteristic of poor metals; however sufficient quantities of them have not yet beensynthesized to examine their chemical properties.

13 14 15 16

AlAluminium

GaGallium

GeGermanium

InIndium

SnTin

SbAntimony

TlThallium

PbLead

BiBismuth

PoPolonium

Uutununtrium

Uuqununquadium

Uupununpentium

Uuhununhexium

External links• Patent-Invent - Poor Metals Quick Facts [7]

• Royal Armouries - Poor Metals [8]

References[1] General Chemistry: Principles and Structure (http:/ / books. google. com/ books?& id=UVlGAAAAYAAJ& dq=post-transition+ metal+

brady& q=post-transition+ "just+ to+ the+ right"#search_anchor) (5th ed.), by James E. Brady, page 96. Published by Wiley, 1990. ISBN0471621315, 9780471621317

[2] Instant Notes in Inorganic Chemistry (http:/ / books. google. com/ books?id=8yQOhvD3tWcC& pg=PA185#v=onepage& q=& f=false) (2nded.), by P.A. Cox, page 185–186. Published by Garland Science/BIOS Scientific Publishers, 2004. ISBN 1859962890, 9781859962893

[3] Nomenclature of Inorganic Chemistry, IUPAC Recommendations (2005) (http:/ / www. iupac. org/ publications/ books/ rbook/Red_Book_2005. pdf) IR 3-6.2 p 51

[4] William B. Jensen (2003). "The Place of Zinc, Cadmium, and Mercury in the Periodic Table". Journal of Chemical Education 80 (8):952–961.

[5] Introductory solid state physics (http:/ / books. google. com/ books?id=w6eAC9y47_4C& pg=PA216#v=onepage& q=& f=false) (2nd ed.),by H.P. Myers, page 216. Published by Taylor & Francis, 1997. ISBN 074840659X, 9780748406593

[6] Bioinorganic Chemistry (http:/ / books. google. com/ books?id=tCOyYeekTSEC& pg=PA69#v=onepage& f=false), by K. Hussain Reddy,page 69. Published by New Age International, 2003. ISBN 8122414370, 9788122414370

[7] http:/ / www. chemistry. patent-invent. com/ chemistry/ poor_metals. html[8] http:/ / www. royalarmouries. org/ extsite/ view. jsp?sectionId=2884

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Transactinide element 137

Transactinide elementIn chemistry, transactinide elements (also, transactinides, or super-heavy elements) are the chemical elementswith atomic numbers greater than those of the actinides, the heaviest of which is lawrencium (103).[1] [2]

Transactinide elements are also transuranic elements, that is, have an atomic number greater than that of uranium(92), an actinide. The further distinction of having an atomic number greater than the actinides is significant inseveral ways:• The transactinide elements all have electrons in the 6d subshell in their ground state (and thus are placed in the

d-block). The last actinide, lawrencium, also has one electron in the 6d subshell.• Except for dubnium, even the longest-lasting isotopes of transactinide elements have extremely short half-lives,

measured in seconds, or smaller units.• The element naming controversy involved the first five or six transactinide elements. These elements thus used

three-letter systematic names for many years after their discovery had been confirmed. (Usually the three-letternames are replaced with two-letter names relatively shortly after a discovery has been confirmed.)

Transactinides are radioactive and have only been obtained synthetically in laboratories. None of these elements hasever been collected in a macroscopic sample. Transactinide elements are all named after nuclear physicists andchemists or important locations involved in the synthesis of the elements.Chemistry Nobelist Glenn T. Seaborg who first proposed the actinide concept which led to the acceptance of theactinide series also proposed the existence of a transactinide series ranging from element 104 to 121 and asuperactinide series approximately spanning elements 122 to 153. The transactinide seaborgium is named in hishonor.The term transactinide is an adjective, and is not commonly used alone as a noun to refer to the transactinideelements.

List of the transactinide elements

• 104 Rutherfordium, Rf• 105 Dubnium, Db• 106 Seaborgium, Sg• 107 Bohrium, Bh• 108 Hassium, Hs• 109 Meitnerium, Mt• 110 Darmstadtium, Ds• 111 Roentgenium, Rg• 112 Copernicium, Cn• 113 Ununtrium, Uut*• 114 Ununquadium, Uuq*• 115 Ununpentium, Uup*• 116 Ununhexium, Uuh*• 117 Ununseptium, Uus*• 118 Ununoctium, Uuo** The synthesis of these elements has not been officially attested by IUPAC, while in several cases previoussyntheses have been confirmed by other institutions or other methods. The names and symbols given are provisionalas no names for the elements have been agreed on.

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Transactinide element 138

See also• Transuranium element• Bose-Einstein condensate (also known as Superatom)• Island of stability

References[1] IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (http:/ / www. iupac. org/ reports/ provisional/

abstract04/ connelly_310804. html) (online draft of an updated version of the "Red Book" IR 3-6)[2] Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, eds (2006). The Chemistry of the Actinide and Transactinide Elements (3rd ed.).

Dordrecht, The Netherlands: Springer. ISBN 13978-1-4020-3555-5.

Transuranium elementIn chemistry, transuranium elements (also known as transuranic elements) are the chemical elements with atomicnumbers greater than 92 (the atomic number of uranium). None of these elements are stable; they decayradioactively into other elements.

Overview

Periodic table with elements colored according to the half-life of their most stable isotope.     Stable elements;      Radioactive elements with very long-lived isotopes.

Their half-lives of over four million years confer them very small, if notnegligible radioactivities;      Radioactive elements that may present low health

hazards. Their most stable isotopes have half-lives between 800 and 34.000years. Because of this, they usually have some commercial applications;

     Radioactive elements that are known to pose high safety risks. Their moststable isotopes have half-lifes between one day and 103 years. Their

radioactivities confers them little potential for commercial uses;      Highlyradioactive elements. Their most stable isotopes have half-lifes between oneday and several minutes. They pose severe health risks. Few of them receiveuses outside basic research;      Extremely radioactive elements. Very little is

known about these elements due to their extreme instability and radioactivity.

Of the elements with atomic numbers 1to 92, all but four (technetium,promethium, astatine, and francium)occur in easily detectable quantities onEarth, having stable, or very longhalf-life isotopes, or are created ascommon products of the decay ofuranium.

All of the elements with higher atomicnumbers, however, have been firstdiscovered in the laboratory, other thanneptunium and plutonium. They are allradioactive, with a half-life muchshorter than the age of the Earth, soany atoms of these elements, if theyever were present at the Earth'sformation, have long since decayed.Trace amounts of neptunium andplutonium form in some uranium-richrock, and small amounts are producedduring atmospheric tests of atomicweapons. The Np and Pu generated arefrom neutron capture in uranium orewith two subsequent beta decays (238U→ 239U → 239Np → 239Pu).

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Transuranium element 139

Those that can be found on Earth now are artificially generated synthetic elements, via nuclear reactors or particleaccelerators. The half lives of these elements show a general trend of decreasing with atomic number. There areexceptions, however, including dubnium and several isotopes of curium. Further anomalous elements in this serieshave been predicted by Glenn T. Seaborg, and are categorised as the “island of stability.”Heavy transuranic elements are difficult and expensive to produce, and their prices go up rapidly with atomicnumber. As of 2008, weapons-grade plutonium cost around $4,000/gram (or roughly 150 times more than gold),[1]

and californium cost $60,000,000/gram.[2] Due to production difficulties, none of the elements beyond californiumhave industrial applications or were ever produced in macroscopic quantities.Transuranic elements that have not been discovered, or have been discovered but are not yet officially named, useIUPAC's systematic element names. The naming of transuranic elements is a source of controversy.

Discovery and naming of transuranium elementsThe majority of the transuranium elements were produced by three groups:• A group at the University of California, Berkeley, under three different leaders:

• Edwin Mattison McMillan, first to produce a transuranium element:• 93. neptunium, Np, named after the planet Neptune, as it follows uranium and Neptune follows Uranus in

the planetary sequence (1940).• Glenn T. Seaborg, next in order, who produced:

• 94. plutonium, Pu, named after the dwarf planet Pluto, following the same naming rule as it followsneptunium and Pluto follows Neptune in the pre-2006 planetary sequence (1940).

• 95. americium, Am, named because it is an analog to europium, and so was named after the continent whereit was first produced (1944).

• 96. curium, Cm, named after Pierre and Marie Curie, famous scientists who separated out the firstradioactive elements (1944).

• 97. berkelium, Bk, named after the city of Berkeley, where the University of California, Berkeley is located(1949).

• 98. californium, Cf, named after the state of California, where the university is located (1950).• Albert Ghiorso, who had been on Seaborg's team when they produced curium, berkelium, and californium,

took over as director to produce:• 99. einsteinium, Es, named after the theoretical physicist Albert Einstein (1952).• 100. fermium, Fm, named after Enrico Fermi, the physicist who produced the first controlled chain reaction

(1952).• 101. mendelevium, Md, named after the Russian chemist Dmitri Mendeleev, credited for being the primary

creator of the periodic table of the chemical elements (1955).• 102. nobelium, No, named after Alfred Nobel (1956).• 103. lawrencium, Lr, named after Ernest O. Lawrence, a physicist best known for development of the

cyclotron, and the person for whom the Lawrence Livermore National Laboratory and the LawrenceBerkeley National Laboratory (which hosted the creation of these transuranium elements) are named(1961).

• A group at the Joint Institute for Nuclear Research in Dubna, Russia (then the Soviet Union) who produced:• 104. rutherfordium, Rf, named after Ernest Rutherford, who was responsible for the concept of the atomic

nucleus (1966).• 105. dubnium, Db, an element that is named after the city of Dubna, where the JINR is located. Also known in

Western circles as "hahnium" in honor of Otto Hahn (1968).

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Transuranium element 140

• 106. seaborgium, Sg, named after Glenn T. Seaborg. This name caused controversy because Seaborg was stillalive, but eventually became accepted by international chemists (1974).

• 107. bohrium, Bh, named after the Danish physicist Niels Bohr, important in the elucidation of the structure ofthe atom (1981).

• A group at the Gesellschaft für Schwerionenforschung (Society for Heavy Ion Research) in Darmstadt, Hessen,Germany, under Peter Armbruster, who produced:• 108. hassium, Hs, named after the Latin form of the name of Hessen, the German Bundesland where this work

was performed (1984).• 109. meitnerium, Mt, named after Lise Meitner, an Austrian physicist who was one of the earliest scientists to

become involved in the study of nuclear fission (1982).• 110. darmstadtium, Ds named after Darmstadt, Germany, the city in which this work was performed (1994).• 111. roentgenium, Rg named after Wilhelm Conrad Röntgen, discoverer of X-rays (1994).• 112. copernicium, Cn named after astronomer Nicolaus Copernicus (1996).

List of the transuranic elements

• Actinides

• 93 neptunium Np• 94 plutonium Pu• 95 americium Am• 96 curium Cm• 97 berkelium Bk• 98 californium Cf• 99 einsteinium Es• 100 fermium Fm• 101 mendelevium

Md• 102 nobelium No• 103 lawrencium Lr

• Transactinide elements

• 104 rutherfordium Rf• 105 dubnium Db• 106 seaborgium Sg• 107 bohrium Bh• 108 hassium Hs• 109 meitnerium Mt• 110 darmstadtium Ds• 111 roentgenium Rg• 112 copernicium Cn• 113 ununtrium Uut*• 114 ununquadium Uuq*• 115 ununpentium Uup*• 116 ununhexium Uuh*• 117 ununseptium Uus*• 118 ununoctium Uuo*

*The existence of these elements has been confirmed, however the names and symbols given are provisional as nonames for the elements have been agreed on.

Super-heavy atoms

Position of the super-heavy elements in the periodic table.

Super-heavy atoms, (super heavy elements, commonlyabbreviated SHE), are the transactinide elementsbeginning with rutherfordium (atomic number 104).They have only been made artificially, and currentlyserve no useful purpose because their short half-livescause them to decay after a few minutes to just a fewmilliseconds, which also makes them extremely hard tostudy.[3] [4]

Super-heavy atoms have all been created during thelatter half of the 20th century and are continually being

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Transuranium element 141

created during the 21st century as technology advances. They are created through the bombardment of elements in aparticle accelerator, for example the nuclear fusion of californium-249 and carbon-12 creates rutherfordium. Theseelements are created in quantities on the atomic scale and no method of mass creation has been found.[3]

See also• Bose-Einstein condensate (also known as Superatom)• Island of stability• Minor actinides• Waste Isolation Pilot Plant, repository for transuranic waste• Extension of the periodic table beyond the seventh period

Further reading• Annotated bibliography for the transuranic elements [5] from the Alsos Digital Library for Nuclear Issues.• Transuranium elements [6]

• Super Heavy Elements network official website [7] (network of the European integrated infrastructure initiativeEURONS)

• Prof. Amnon Marinov's Site with related publications [8]

• Darmstadium and beyond [9]

References[1] "Price of Plutonium" (http:/ / hypertextbook. com/ facts/ 2008/ AndrewMorel. shtml). The Physics Factbook. .[2] Rodger C. Martin and Steven E. Kos. "Applications and Availability of Californium-252 Neutron Sources for Waste Characterization" (http:/

/ www. ornl. gov/ ~webworks/ cpr/ pres/ 108701_. pdf) (pdf). .[3] Heenen, P. H.; Nazarewicz, W. (2002). "Quest for superheavy nuclei". Europhysics News 33: 5. doi:10.1051/epn:2002102.[4] Greenwood, N. N. (1997). "Recent developments concerning the discovery of elements 100-111". Pure and Applied Chemistry 69: 179.

doi:10.1351/pac199769010179.[5] http:/ / alsos. wlu. edu/ qsearch. aspx?browse=science/ Transuranium+ Elements[6] http:/ / web. fccj. org/ ~ethall/ uranium/ uranium. htm[7] http:/ / www. transfermium. net/[8] http:/ / www. phys. huji. ac. il/ ~marinov/ index. htm[9] http:/ / pubs. acs. org/ cen/ 80th/ darmstadtium. html

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Transition metalThe term transition metal (sometimes also called a transition element) has two possible meanings:• In the past it referred to any element in the d-block of the periodic table, which includes groups 3 to 12 on the

periodic table. All elements in the d-block are metals. (In actuality, the f-block is also included in the form of thelanthanide and actinide series.)

• The modern, IUPAC definition[1] states that a transition metal is "an element whose atom has an incomplete dsub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transitionmetals in this definition.

Jensen[2] has reviewed the historical usage of the terms transition element (or metal) and d-block. The word"transition" was first used to describe the elements now known as the d-block by the English chemist Charles Buryin 1921, who referred to a transition series of elements during the change of an inner layer of electrons (for examplen=3 in the 4th row of the periodic table) from a stable group of 8 to one of 18, or from 18 to 32.[3]

ClassificationIn the d-block the atoms of the elements have between 1 and 10 d electrons. The following table shows IUPACdefinition of what is called "transition metal".

Group 3 4 5 6 7 8 9 10 11 12

Period 4 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30

Period 5 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48

Period 6 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80

Period 7 Rf 104 Db105

Sg106

Bh 107 Hs 108 Mt 109 Ds 110 Rg 111 Cn 112

Atoms of scandium and yttrium have a single d electron in the outermost shell, and thus are mostly consideredtransition metals. However, as all their compounds contain the ions Sc3+ and Y3+ in which there are no d electrons,these elements are not universally considered transition metals. This is disputed by people saying that classificationmust be lead by neutral atoms properties, and fact zirconium and titanium compounds also don't contain d-electrons.The two vacant places in group 3 is due to the fact that, for period 6, the place is disputed between lanthanum andlutetium and for period 7, between actinium and lawrencium . To prevent this, IUPAC placed all of these 4 aslanthanoids/actinoids, which makes both series 15 elements long, despite fact there are only 14 f-electrons possibleand then f-block can't be any longer. This means IUPAC lanthanoids/actinoids contains one d-element. Modernscientists usually claim Lu and Lr as d-block elements rather La and Ac, however, both variants are widely used.The electronic structure of transition metal atoms can be written, with a few minor exceptions, as [Ng]ns2(n-1)dm, asthe inner d orbital has more energy than the valence-shell s orbital. In divalent and trivalent ions of the transitionmetals the situation is reversed so that the s electrons have higher energy. Consequently an ion such as Fe2+ has no selectrons, it has the electronic configuration [Ar]3d6 as compared with the configuration of the atom, [Ar]4s23d6.According to IUPAC, Zinc, cadmium, mercury and copernicium are transition metals, although some say they are not.[2] as they have the electronic configuration [Ng]d10s2, with no incomplete d shell.[4] People who count Zn, Cd and Hg as post-transition mention that in the oxidation state +2 the ions have the electronic configuration [ Ng ] d10. and while compounds in the +1 oxidation state, such as Hg2

2+, are known there are no unpaired electrons because of the formation of a covalent bond between the two atoms of the dimer. However, it is opposed by opinion that d-block must be equal by its content to transition metals, because if mercury has no incompleteness in d-orbital, thus ytterbium has no incompleteness in f-orbital and is a transition metal. Also, judging on some separated properties

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Transition metal 143

(like Irving-Williams series of stability constants of complexes) is also mostly denied.

Characteristic propertiesThere are a number of properties shared by the transition elements that are not found in other elements, which resultsfrom the partially filled d shell. These include• the formation of compounds whose colour is due to d - d electronic transitions• the formation of compounds in many oxidation states, due to the relatively low reactivity of unpaired d

electrons.[5]

• the formation of many paramagnetic compounds due to the presence of unpaired d electrons. A few compounds ofmain group elements are also paramagnetic (e.g. nitric oxide, oxygen)

Coloured compounds

From left to right, aqueous solutions of: Co(NO3)2 (red); K2Cr2O7(orange); K2CrO4 (yellow); NiCl2 (turquoise); CuSO4 (blue); KMnO4

(purple).

Colour in transition-series metal compounds isgenerally due to electronic transitions of two principaltypes.• charge transfer transitions. An electron may jump

from a predominantly ligand orbital to apredominantly metal orbital, giving rise to aligand-to-metal charge-transfer (LMCT) transition.These can most easily occur when the metal is in ahigh oxidation state. For example, the colour ofchromate, dichromate and permanganate ions is dueto LMCT transitions. A metal-to ligand charge transfer (MLCT) transition will be most likely when the metal is ina low oxidation state and the ligand is easily oxidised. Mercuric iodide, HgI2, is red because of a MLCTtransition. As this example shows, charge transfer transitions are not restricted to transition metals.[6]

• d-d transitions. An electron jumps from one d-orbital to another. In complexes of the transition metals the dorbitals do not all have the same energy. The pattern of splitting of the d orbitals can be calculated using crystalfield theory. The extent of the splitting depends on the particular metal, its oxidation state and the nature of theligands. The actual energy levels are shown on Tanabe-Sugano diagrams.

In centrosymmetric complexes, such as octahedral complexes, d-d transitions are forbidden by the Laporte rule andonly occur because of vibronic coupling in which a molecular vibration occurs together with a d-d transition.Tetrahedral complexes have somewhat more intense colour because mixing d and p orbitals is possible when there isno centre of symmetry, so transitions are not pure d-d transitions. The molar absorptivity (ε) of bands caused by d-dtransitions are relatively low, roughly in the range 5-500 M−1cm−1 (where M = mol dm−3).[7] Some d-d transitionsare spin forbidden. An example occurs in octahedral, high-spin complexes of manganese(II), which has a d5

configuration in which all five electron has parallel spins; the colour of such complexes is much weaker than incomplexes with spin-allowed transitions. In fact many compounds of manganese(II) appear almost colourless. Thespectrum of [Mn(H2O)6]2+ shows a maximum molar absorptivity of about 0.04 M−1cm−1 in the visible spectrum.

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Transition metal 144

Oxidation statesA characteristic of transition metals is that they exhibit two or more oxidation states, usually differing by one. Forexample, compounds of vanadium are known in all oxidation states between −1, such as [V(CO)6]−, and +5, such asVO3−

4.Main group elements in groups 13 to 17 also exhibit multiple oxidation states. The "common" oxidation states ofthese elements typically differ by two. For example, compounds of gallium in oxidation states +1 and +3 exist inwhich there is a single gallium atom. No compound of Ga(II) is known: any such compound would have an unpairedelectron and would behave as a free radical and be destroyed rapidly. The only compounds in which gallium has aformal oxidation state of +2 are dimeric compounds, such as [Ga2Cl6]2−, which contain a Ga-Ga bond formed fromthe unpaired electron on each Ga atom.[8] Thus the main difference in oxidation states, between transition elementsand other elements is that oxidation states are known in which there is a single atom of the element and one or moreunpaired electrons.The maximum oxidation state in the first row transition metals is equal to the number of valence electron fromtitanium (+4) up to manganese (+7), but decreases in the later elements. In the second and third rows the maximumoccurs with ruthenium and osmium (+8). In compounds such as [MnO4]− and OsO4 the elements achieve a stableoctet by forming four covalent bonds.The lowest oxidation states are exhibited in such compounds as Cr(CO)6 (oxidation state zero) and [Fe(CO)4]2−

(oxidation state −2) in which the 18-electron rule is obeyed. These complexes are also covalent.Ionic compounds are mostly formed with oxidation states +2 and +3. In aqueous solution the ions are hydrated by(usually) six water molecules arranged octahedrally.

MagnetismTransition metal compounds are paramagnetic when they have one or more unpaired d electrons.[9] In octahedralcomplexes with between four and seven d electrons both high spin and low spin states are possible. Tetrahedraltransition metal complexes such as [FeCl4]2− are high spin because the crystal field splitting is small so that theenergy to be gained by virtue of the electrons being in lower energy orbitals is always less that the energy needed topair up the spins. Some compounds are diamagnetic. These include octahedral, low-spin, d6 and square-planar d8

complexes. In these cases, crystal field splitting is such that all the electrons are paired up.Ferromagnetism occurs when individual atoms are paramagnetic and the spin vectors are aligned parallel to eachother in a crystalline material. Metallic iron and the alloy alnico are examples of ferromagnetic materials involvingtransition metals. Antiferromagnetism is another example of a magnetic property arising from a particular alignmentof individual spins in the solid state.

See also• Inner transition element, a name given to any member of the f-block• Ligand field theory a development of crystal field theory taking covalency into account• Post-transition metal

References[1] International Union of Pure and Applied Chemistry. " transition element (http:/ / goldbook. iupac. org/ T06456. html)". Compendium of

Chemical Terminology Internet edition.[2] Jensen, William B. (2003). "The Place of Zinc, Cadmium, and Mercury in the Periodic Table" (http:/ / www. uv. es/ ~borrasj/ ingenieria_web/

temas/ tema_1/ lecturas_comp/ p952. pdf). Journal of Chemical Education 80 (8): 952–961. doi:10.1021/ed080p952. .[3] "Langmuir's theory of the arrangement of electrons in atoms and molecules" C.R. Bury, J. Amer. Chem. Soc. 43, p.1602-1609 (1921)[4] Cotton, F. Albert; Wilkinson, G.; Murillo, C. A. (1999). Advanced Inorganic Chemistry (6th ed.). New York: Wiley.

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Transition metal 145

[5] Matsumoto, Paul S (2005). "Trends in Ionization Energy of Transition-Metal Elements" (http:/ / www. jce. divched. org/ Journal/ Issues/2005/ Nov/ abs1660. html). Journal of Chemical Education 82: 1660. doi:10.1021/ed082p1660. .

[6] T.M. Dunn in Lewis, J.; Wilkins,R.G. (1960). Modern Coordination Chemistry. New York: Interscience., Chapter 4, Section 4, "ChargeTransfer Spectra", pp. 268-273.

[7] Orgel, L.E. (1966). An Introduction to Transition-Metal Chemistry, Ligand field theory (2nd. ed.). London: Methuen.[8] Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0080379419 p.

240[9] Figgis, B.N.; Lewis, J. (1960). Lewis, J. and Wilkins, R.G.. ed. The Magnetochemistry of Complex Compounds. Modern Coordination

Chemistry. New York: Interscience. pp. 400–454.

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146

See also

Table of nuclides

A chart of nuclides (cut into three parts for betterpresentation).

A table of nuclides or chart of nuclides is a two-dimensional graph inwhich one axis represents the number of neutrons and the otherrepresents the number of protons in an atomic nucleus. Each pointplotted on the graph thus represents the nuclide of a real orhypothetical chemical element. This system of ordering nuclides canoffer a greater insight into the characteristics of isotopes than thebetter-known periodic table, which shows only elements instead ofeach of their isotopes.

Description and utilityA chart or table of nuclides (capitalization optional) is a simple map to the nuclear, or radioactive, behaviour ofnuclides, as it distinguishes the isotopes of an element. It contrasts with a periodic table, which only maps theirchemical behavior, since isotopes of the same element do not differ chemically. Nuclide charts organize isotopesalong the X axis by their numbers of neutrons and along the Y axis by their numbers of protons, out to the limits ofthe neutron and proton drip lines. This representation was first published by Giorgio Fea in 1935,[1] and expanded byEmilio Segrè in 1945 or G. Seaborg. In 1958, Walter Seelmann-Eggebert and Gerda Pfennig published the firstedition of the Karlsruhe Nuclide Chart. Its 7th edition was made available in 2006. Today, one finds several nuclidecharts, four of them have a wide distribution: the Karlsruhe Nuclide Chart, the Strasbourg Universal Nuclide Chart,the Chart of the Nuclides from the JAEA and the Nuclide Chart from Knolls Atomic Power Laboratory.[2] It hasbecome a basic tool of the nuclear community.

Trends in the Chart of Nuclides

5 6H 7He 8Li 9Be 10B 11C 12N 13O 14F Ne 11

6 7H 8He 9Li 10Be 11B 12C 13N 14O 15F 16Ne Na 12

7 9He 10Li 11Be 12B 13C 14N 15O 16F 17Ne 18Na Mg 13

8 10He 11Li 12Be 13B 14C 15N 16O 17F 18Ne 19Na 20Mg Al 14

9 12Li 13Be 14B 15C 16N 17O 18F 19Ne 20Na 21Mg 22Al Si

• Isotopes are nuclides with the same number of protons but differing numbers of neutrons; that is, they have thesame atomic number and are therefore the same chemical element. Isotopes neighbor each other vertically e.g.Carbon-12, Carbon-13, and Carbon-14 in the sample table above.

• Isotones are nuclides with the same number of neutrons but differing number of protons. Isotones neighbor eachother horizontally. Example: Carbon-14, Nitrogen-15, Oxygen-16 in the sample table above.

• Isobars are nuclides with the same number of nucleons, i.e. mass number, but different numbers of protons and different number of neutrons. Isobars neighbor each other diagonally from lower-left to upper-right. Example:

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Table of nuclides 147

Carbon-14, Nitrogen-14, Oxygen-14 in the sample table above.• Beyond the neutron drip line along the lower left, nuclides decay by neutron emission.• Beyond the proton drip line along the upper right, nuclides decay by proton emission. Drip lines have only been

established for some elements.• The island of stability is a hypothetical region of the table of nuclides that contains isotopes far more stable than

other transuranic elements.• There are no stable atoms having an equal number of protons and neutrons in their nuclei with atomic number

greater than 20 as can be readily "read" from the chart. Nuclei of greater atomic number require an excess ofneutrons for stability.

• There are no stable atoms having atomic number greater than Z=82 (lead)[3] . Atoms with atomic numbers of 82and lower all have stable isotopes, with the exceptions of technetium (Z=43) and promethium (Z=61).

Available representations

Charts of the nuclides

article description

Table of nuclides (complete) Presents the data via a single, contiguous chart that requires both vertical and horizontal scrolling to view all itscontents (262 kB total HTML download).

Table of nuclides(segmented, wide)

Presents the data via four separate charts, each typically with 30 elements. Depending on the browser, no horizontalscrolling is required in window widths of at least 1225 to 1440 pixels (311 kB total HTML download).

Table of nuclides(segmented, narrow)

Presents the data via eight separate charts, each typically with 15 elements. Horizontal scrolling is not required forall but the smallest computer monitors (321 KB total HTML download).

Table of nuclides (sorted byhalf-life)

Presents the data in a one-dimensional list where all nuclides are sorted by their half-life, including specific massexcess and decay-modes, no horizontal scrolling is required (95  kB total HTML download).

Table of nuclides (combined) Provides both the eight-chart, segmented presentation and the single, contiguous chart. Provides quick-jumphyperlinks to jump between the two. Features expanded introductory text for first-time readers. (588 kB total HTMLdownload).

File:NuclideMap.PNG Single image (not HTML) of the National Nuclear Data Center chart from the NuDat 2 database (3.9 MB)

Articles on isotopes of an element

article description

Index to isotopepages

A periodic table that provides links to a separate article on each element and its isotopes.

Isotope lists A page that provides data on the isotopes of each element in groups of 24 elements.

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Table of nuclides 148

See also• List of nuclides. Presents information in list form, and in order of stability, for the 905 nuclides which are stable,

or are radioactive with half lives greater than 60 minutes.

External links• Karlsruhe Nuclide Chart [4]

• Universal Nuclide Chart [5]

• Interactive Chart of Nuclides (Brookhaven National Laboratory) [6]

• The Lund/LBNL Nuclear Data Search [7]

• Another example of a Chart of Nuclides from Korea [8]

• YChartElements [19] dynamic periodic table and chart of the nuclides, a Yoix application

•Compact Chart of Nuclides (non-standard representation with elements along a diagonal) 70x70. [9]

• The Live Chart of Nuclides - IAEA [20] in Java [20] or HTML [21]

• Map of the Nuclides [10]

References[1] Georgio Fea. Il Nuovo Cimento 2 (1935) 368[2] "What We Do: The Chart of Nuclides" (http:/ / www. knollslab. com/ nuclides. html). Knolls Atomic Power Laboratory. . Retrieved 14 May

2009.[3] Holden,CRC Handbook of Chemistry and Physics, 90th Edition §11[4] http:/ / www. karlsruhenuclidechart. net[5] http:/ / www. nucleonica. net/ unc. aspx[6] http:/ / www. nndc. bnl. gov/ chart[7] http:/ / nucleardata. nuclear. lu. se/ nucleardata/ toi/[8] http:/ / atom. kaeri. re. kr[9] http:/ / adavidstubbs. home. comcast. net/ ~adavidstubbs/ Quark/ Isotope_table_(compact). htm[10] http:/ / t2. lanl. gov/ data/ map. html

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Island of stability

3-dimensional rendering of the theoretical Island of Stability.

The island of stability is a term fromnuclear physics that describes thepossibility of elements withparticularly stable "magic numbers" ofprotons and neutrons. This wouldallow certain isotopes of sometransuranium elements to be far morestable than others; that is, to decaymuch more slowly (with half-lives ofat least minutes or days, compared tofractions of a second; some have evensuggested the possibility of half-liveson the order of millions of years[1] ).

HistoryThe idea of the island of stability was first proposed by Glenn T. Seaborg. The hypothesis is that the atomic nucleusis built up in "shells" in a manner similar to the electron shells in atoms. In both cases shells are just groups ofquantum energy levels that are relatively close to each other. Energy levels from quantum states in two differentshells will be separated by a relatively large energy gap. So when the number of neutrons and protons completely fillthe energy levels of a given shell in the nucleus, the binding energy per nucleon will reach a local maximum and thusthat particular configuration will have a longer lifetime than nearby isotopes that do not have filled shells.[2]

A filled shell would have "magic numbers" of neutrons and protons. One possible magic number of neutrons forspherical nuclei is 184, and some possible matching proton numbers are 114, 120 and 126 – which would mean thatthe most stable spherical isotopes would be ununquadium-298, unbinilium-304 and unbihexium-310. Of particularnote is Ubh-310, which would be "doubly magic" (both its proton number of 126 and neutron number of 184 arethought to be magic) and thus the most likely to have a very long half-life. (The next lighter doubly-magic sphericalnucleus is lead-208, the heaviest stable nucleus and most stable heavy metal.) Isotopes of elements in the rangebetween 110 through 114 have been found to decay more slowly than isotopes of nuclei nearby in the periodic table.However, recent research indicates that large nuclei are deformed, causing magic numbers to shift. Hassium-270 isnow believed to be doubly-magic nucleus, with deformed magic numbers 108 and 162. Its half-life may be as high as23 seconds.[3] [4]

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Island of stability 150

Half-lives of large isotopes

Periodic table with elements colored according to the half-life of their most stable isotope.     Stable elements.      Radioactive elements with half-lives of over four millionyears.      Half-lives between 800 and 34,000 years.      Half-lives between 1 day

and 103 years.      Half-lives ranging between several minutes and 1 day.     Extremely radioactive elements with half-lives less than a minute.

Fermium is the heaviest element thatcan be produced in a nuclear reactor.The stability (half-life of thelongest-lived isotope) of elementsgenerally decreases from element 101to element 109 and then approaches anisland of stability with longer-livedisotopes in the range of elements 111and 114.[5] The longest-lived observedisotopes are shown in the followingtable.

Known isotopes of elements 100 through 118[5] [6]

Number Name Longest-livedmeasured isotope

Half-life Article

100 Fermium 257Fm 101 days Isotopes of fermium

101 Mendelevium 258Md 52 days Isotopes of mendelevium

102 Nobelium 259No 58 minutes Isotopes of nobelium

103 Lawrencium 262Lr 3.6 hours Isotopes of lawrencium

104 Rutherfordium 267Rf 1.3 hours Isotopes of rutherfordium

105 Dubnium 268Db 29 hours Isotopes of dubnium

106 Seaborgium 271Sg 1.9 minutes Isotopes of seaborgium

107 Bohrium 270Bh 61 seconds Isotopes of bohrium

108 Hassium 277Hs 16.5 minutes Isotopes of hassium

109 Meitnerium 278Mt ~8 seconds Isotopes of meitnerium

110 Darmstadtium 281Ds 11 seconds Isotopes of darmstadtium

111 Roentgenium 281Rg 22.8 seconds Isotopes of roentgenium

112 Copernicium 285Cn 29 seconds Isotopes of copernicium

113 Ununtrium 286Uut 19.6 seconds Isotopes of ununtrium

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Island of stability 151

114 Ununquadium 289Uuq 2.6 seconds Isotopes of ununquadium

115 Ununpentium 289Uup 220 ms Isotopes of ununpentium

116 Ununhexium 293Uuh 61 ms Isotopes of ununhexium

117 Ununseptium 294Uus 78 ms Isotopes of ununseptium

118 Ununoctium 294Uuo 0.89 ms Isotopes of ununoctium

(Note that for elements 109-118 the longest-lived known isotope is always the heaviest one discovered, making it likely that there are still

longer-lived isotopes among the undiscovered heavier ones)

The half-lives of elements in the island are uncertain due to the small number of atoms manufactured and studied todate. Many physicists think they are relatively short, on the order of minutes, hours, or perhaps days. However, sometheoretical calculations indicate that their half-lives may be long (some calculations put it on the order of 109

years).[7] It is possible that these elements could have unusual chemical properties, and, if long-lived enough, variousapplications (such as targets in nuclear physics and neutron sources). However, the isotopes of several of theseelements still have too few neutrons to be stable. The island of stability still has not been reached, since the island's"shores" are more neutron rich than nuclides that have been experimentally produced.The alpha-decay half-lives of 1700 nuclei with 100 ≤ Z ≤ 130 have been calculated in a quantum tunneling modelwith both experimental and theoretical alpha-decay Q-values.[8] [9] [10] [11] [12] [13] The theoretical calculations are ingood agreement with the available experimental data.

Island of relative stability232Th (thorium), 235U and 238U (uranium) are the only naturally occurring isotopes beyond bismuth that arerelatively stable over the current lifespan of the universe. Bismuth was found to be unstable in 2003, with anα-emission half-life of 1.9×1019 years for Bi-209. All other isotopes beyond bismuth are relatively or very unstable.So the main periodic table ends at bismuth, with an island at thorium and uranium. Between bismuth and thoriumthere is a "sea of instability", which renders such elements as astatine, radon, and francium extremely short-livedrelative to all but the heaviest elements found so far.Current theoretical investigation indicates that in the region Z=106–108 and N≈160–164, a small ‘island/peninsula’might be stable with respect to fission and beta decay, such superheavy nuclei undergoing only alpha decay.[9] [10]

[11] Also, 298114 is not the center of the magic island as predicted earlier.[14] On the contrary, the nucleus withZ=110, N=183 appears to be near the center of a possible 'magic island' (Z=104–116, N≈176–186). In the N≈162region the beta-stable, fission survived 268106 is predicted to have alpha-decay half-life ~3.2hrs that is greater thanthat (~28s) of the deformed doubly-magic 270108.[15] The superheavy nucleus 268106 has not been produced in thelaboratory as yet (2009). For superheavy nuclei with Z>116 and N≈184 the alpha-decay half-lives are predicted to beless than one second. The nuclei with Z=120, 124, 126 and N=184 are predicted to form spherical doubly-magicnuclei and be stable with respect to fission.[16] Calculations in a quantum tunneling model show that suchsuperheavy nuclei would undergo alpha decay within microseconds or less.[9] [10] [11]

Synthesis problemsManufacturing nuclei in the island of stability may be very difficult, because the nuclei available as starting materials do not deliver the necessary sum of neutrons. So for the synthesis of isotope 298 of element 114 by using plutonium and calcium, one would require an isotope of plutonium and one of calcium, which have together a sum of at least 298 nucleons (more is better, because at the nuclei reaction some neutrons are emitted). This would require, for example, the use of calcium-50 and plutonium-248 for the synthesis of element 114. However these isotopes (and heavier calcium and plutonium isotopes) are not available in weighable quantities. This is also the case for other

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Island of stability 152

target-projectile combinations.However it may be possible to generate the isotope 298 of element 114, if the multi-nucleon transfer reactions wouldwork in low-energy collisions of actinide nuclei.[17] One of these reactions may be:

248Cm + 238U → 298Uuq + 186W + 2 1n

Quest for the island of stability"We search for the island of stability because, like Mount Everest, it is there. But, as with Everest, there isprofound emotion, too, infusing the scientific search to test a hypothesis. The quest for the magic island showsus that science is far from being coldness and calculation, as many people imagine, but is shot through withpassion, longing and romance."—Oliver Sacks[18]

See also• Island of stability: Ununquadium — Unbinilium — Unbihexium• Table of nuclides — a visualization of the island of stability• Periodic table and Periodic table (extended)

External links• Hunting the biggest atoms in the universe [19] (July 23, 2008)• The hunt for superheavy elements [20] (April 7, 2008)• The synthesis of spherical superheavy nuclei in 48Ca induced reactions [21] (needs login so can not access !)• Uut and Uup Add Their Atomic Mass to Periodic Table [22] (Feb 2004)• New elements discovered and the island of stability sighted [23] (Aug 1999 - includes report on article later

retracted)• First postcard from the island of nuclear stability [24] (1999)• Second postcard from the island of stability [25] (Oct 2001)• Superheavy Elements "Island of Stability" [26] (single text slide - undated)• Superheavy elements [27] (Jul 2004 Yuri Oganessian of JINR )• Can superheavy elements (such as Z=116 or 118) be formed in a supernova? Can we observe them? [28]

• NOVA - Island of Stability [29]

• New York Times Editorial by Oliver Sacks regarding the Island of Stability theory [30] (Feb 2004 re 113 and 115)

References[1] "Superheavy Element 114 Confirmed: A Stepping Stone to the Island of Stability" (http:/ / www. physorg. com/ news173028810. html). .

Retrieved 11 October 2009.[2] "Shell Model of Nucleus" (http:/ / hyperphysics. phy-astr. gsu. edu/ hbase/ nuclear/ shell. html). HyperPhysics. Department of Physics and

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dokserv?idn=985213566& dok_var=d1& dok_ext=pdf& filename=985213566. pdf). Technischen Universität München. .[4] Dvorak, J.; Brüchle, W.; Chelnokov, M.; Dressler, R.; Düllmann, Ch.; Eberhardt, K.; Gorshkov, V.; Jäger, E. et al. (2006). "Doubly Magic

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[14] Sven Gösta Nilsson, Chin Fu Tsang, Adam Sobiczewski, Zdzislaw Szymaski, Slawomir Wycech, Christer Gustafson, Inger-Lena Lamm,Peter Möller and Björn Nilsson (February 14, 1969). "On the nuclear structure and stability of heavy and superheavy elements". NuclearPhysics A 131 (1): 1–66. doi:10.1016/0375-9474(69)90809-4.

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[18] "Greetings From the Island of Stability" (http:/ / www. nytimes. com/ 2004/ 02/ 08/ opinion/ 08SACK. html?ex=1391576400&en=68476e9da837f91f& ei=5007& partner=USERLAND& pagewanted=all), Opinion in the New York Times, February 8, 2004

[19] http:/ / www. newscientist. com/ article/ mg19926661. 200-hunting-the-biggest-atoms-in-the-universe. html?full=true[20] http:/ / arxivblog. com/ ?p=350[21] http:/ / 159. 93. 28. 88/ popeko/ e114_287. html[22] http:/ / www. radiochemistry. org/ periodictable/ elements/ 115. html[23] http:/ / www. ias. ac. in/ currsci/ aug10/ articles9. htm[24] http:/ / www. cerncourier. com/ main/ article/ 39/ 7/ 18[25] http:/ / www. cerncourier. com/ main/ article/ 41/ 8/ 17[26] http:/ / imglib. lbl. gov/ ImgLib/ COLLECTIONS/ BERKELEY-LAB/ SEABORG-ARCHIVE/ index/ 96B05658. html[27] http:/ / physicsweb. org/ articles/ world/ 17/ 7/ 7[28] http:/ / curious. astro. cornell. edu/ question. php?number=599[29] http:/ / www. pbs. org/ wgbh/ nova/ sciencenow/ 3313/ 02. html[30] http:/ / www. nytimes. com/ 2004/ 02/ 08/ opinion/ 08SACK. html?ex=1391576400& en=68476e9da837f91f& ei=5007&

partner=USERLAND

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Article Sources and ContributorsPeriodic table  Source: http://en.wikipedia.org/w/index.php?oldid=382320968  Contributors: 129.186.19.xxx, 158.252.248.xxx, 1993 lol, 203.109.250.xxx, 64.26.98.xxx, A-giau, A. di M.,Aa35te, Abc518, Aciddoll, Aco47, Adam Bishop, Adamsbriand, Adashiel, AdiJapan, AdjustShift, Adult Swim Addict, Af648, Ageekgal, Ahoerstemeier, AlHalawi, Alansohn, AlimanRuna,Alkivar, Allstarecho, Alphachimp, Altenmann, Alvinrune, Ambuj.Saxena, Anastrophe, Andre Engels, Andrew11, Andrewrost3241981, Android 93, Andy120290, Angrysockhop, Angusmclellan,AnjuX, Anna Lincoln, Anoop.m, Antandrus, Aonrotar, Apastrophe, Arbitrarily0, Archenzo, Archimerged, Arjun Rana, Arkrishna, Arman Cagle, Asyndeton, Aushulz, Avicennasis, Avsa, AxG,AxelBoldt, Az1568, AzaToth, BRG, BTolli, BalkanFever, Barneca, Bcorr, Beanyk, Beetstra, Benbest, Bensaccount, Betaeleven, Bevo, Bigsnake 19, Bigtimepeace, Bill Sayre, Bkell, Bkonrad,Black and White, Blanchardb, Blargblarg89, Blobglob, BlueEarth, Bluemoose, Bob, Bob Jonkman, Bobblewik, Bobby131313, Bobet, Bobo192, Bonaparte, Borgdylan, Borislav, Bovineone,Brendan Moody, BrianKnez, BrianScanlan, Brianga, Briséis, Brockert, BrotherFlounder, Bryan Derksen, Btg2290, C0RNF1AK35, CBM, Cacycle, Caesura, Caknuck, Caltas, Can't sleep, clownwill eat me, Canderson7, Canjth, CapitalR, Car132, Carbon-16, Caster23, Cataclysm, CharlesC, Chengyq19942007, ChickenMarengo, Chill doubt, Cholmes75, Chris 73, Chris the speller,ChrisDHDR, ChrisSmol, Chrisk12, Christian List, Christophenstein, Cimex, Ckatz, Clawson, Clemwang, ClockworkSoul, Clorox, Closedmouth, Cobaltcigs, Coffee, Computerjoe, Conget,ConnTorrodon, Conny, Corpx, Corsair18, Corvus cornix, Courcelles, Cpl Syx, Creator58, Cryptic C62, Cst17, Ctachme, Cwolfsheep, Cyan, D6, DBragagnolo, DMacks, DNAmaster, DR04,DRosenbach, DSachan, DVD R W, Dagrimdialer619, Dale101usa, Dalta, Damnreds, Dan Koehl, DanKeshet, DancingPenguin, Danski14, Darklama, Darrien, Darth Panda, Darthchaos, Davewild,David Edgar, David Gerard, David Little, DavidOaks, Dawn Bard, Dbchip, Dcljr, Ddon, Debresser, Deeptrivia, Deeryh01, Degg444, Dekisugi, Dellacomp, Delldot, DeltaQuad, Den fjättradeankan, Denelson83, Deon, DerHexer, Derek.cashman, Deus Ex, Dffgd, Dhollm, Digger3000, Dillard421, Dinamik, Discospinster, DixonD, Dlorang, Dmmaus, Dmoss, DocWatson42, Dogposter,Dougofborg, Dpbsmith, Dpeters11, Dreadstar, Dreamyshade, Drova, Drunkenmonkey, Dtgm, Dustimagic, Dwaipayanc, Dyknowsore, EH74DK, EL Willy, EagleOne, EamonnPKeane,EarthmatriX, EconoPhysicist, Edcolins, Eddideigel, Edgar181, Egil, Eirik (usurped), El C, Elcobbola, Eli84, Eliashedberg, Elk Salmon, Elkman, Elly4web, Elsweyn, Emperorbma,EnDaLeCoMpLeX, EncMstr, EngineerScotty, Enviroboy, Eric119, Erik Zachte, Escape Orbit, Essam Sharaf, Eszett, EugeneZelenko, Eupedia, Everybody's Got One, Everyking, Excirial, Exert,Exigentsky, Exodecai101, Extransit, FF2010, Fabartus, Feline1, Felix Wan, Femto, Fifo, Figma, Finngall, Fishekad, FisherQueen, FlyingToaster, Fonzy, Fork me, Fredrik, FreplySpang, Full On,Fuzzform, Fyandcena, GDonato, GHe, GabrielF, Gadfium, Garudabd, Gawaxay, Gemmi3, Gentgeen, GeorgeTopouria, Georgedriver, Gffootball58, Ghirlandajo, Giftlite, Gilliam, Giraffedata,Glenn L, Gobonobo, Gona.eu, Gonzonoir, Gopal81, Gprince007, Grahamec, Graniggo, Grick, Grim23, Gromlakh, Gurch, Gurchzilla, Gwernol, HGB, HLewis, Haeleth, Hairy Dude, Hak-kâ-ngìn,HalfShadow, Hamilton hogs, Hamtechperson, Hdt83, Headbomb, Helixblue, Heron, HiDrNick, Hiddenfromview, Honeycake, Hughbert512369, Hut 8.5, Hv, Hwn tls, Hyuuganeji0123, I2yu, IanFraser at Temple Newsam House, IanManka, Icairns, Ilovestars89, Imawsome 09, Imnotminkus, Infrogmation, Inkypaws, Insanity Incarnate, Into The Fray, Iosef, Islander, Itub, Iwilcox, Ixfd64,J.delanoy, J0lt C0la, JDT1991, JForget, JRSP, Jachapo, Jack the Stripper, Jackfork, Jaeger Lotno, Jared Preston, Jauerback, Jaxl, Jaybo007, Jazjaz92, Jdrewitt, Jean-claude perez, Jeff G., Jeffq,JenR32, Jengod, Jhd, Jiang, Jimmy Slade, JinJian, Jinglesmells999, Jklin, Jmocenigo, Jni, Jobroluver98, JodyB, Joeclark, John254, JohnWittle, Johnlogic, Johnnieblue, Jojit fb, Joka1991,Jonmwang, Jose77, Joshlepaknpsa, Jossi, Jpatokal, Juanpdp, Junglecat, Jusjih, Just James, Just another user 2, Juve82, Jwissick, Kaeso Dio, Kaiba, Kaischwartz, Kangxi emperor6868, Kanonkas,Kateshortforbob, Kathryn NicDhàna, Kbdank71, Keegan, Keenan Pepper, Kelvin35, Kerotan, Kesac, Ketsuekigata, Khalid Mahmood, Kingpin13, Kinston eagle, Kiran the great, Kitrkatr,Kiwi137, Klenje, Knowhow, KnowledgeOfSelf, Konczewski, Kosebamse, KotVa, Kragenz, Kungfuadam, Kwamikagami, Kwekubo, Kwertii, La Pianista, Lani123, LeaveSleaves, Lee DanielCrocker, LegitimateAndEvenCompelling, Lightmouse, Lincmad, Littlealien182, LiveAgain, LizardJr8, Logical2u, Lollerskates, Lowellian, LtPowers, Lucent, Luckas Blade, Lucky 6.9,LuigiManiac, Lumos3, Luna Santin, Lupin, Luuva, MER-C, Mac Davis, MacTire02, Madhero88, MairAW, ManiF, MarcoTolo, Marek69, Martin451, 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of the Wizards, Philip Trueman, Philippe, Philthecow, Phisite, Physchim62, Pi Guy 31415, PiMaster3, Piano nontroppo, Pickweed, PierreAbbat, Pinethicket, Piolinfax, Pirateer, Pitcroft, Plumbago, Plutonium55, Poccil, PoliteCarbide, Poor Yorick, PostScript, Precious Roy, PrestonH, Psinu, Psycho Kirby,Ptdecker, Pumeleon, Pwntskater, Quilbert, Qxz, RDBrown, RG2, RJFJR, RJHall, RUL3R, Racantrell, Radagast, RadiantRay, Ragesoss, Ran, Rarb, Rasmus vendelboe, Rawling, Realm up,Redaktor, Reddi, Reedy, Rescorbic, Rettetast, RexNL, Rfc1394, Rich Farmbrough, Richard777, RichardF, Rifleman 82, Rihanij, Rintrah, Rjstott, Robert Skyhawk, RobertG, Roentgenium111,Romanm, Ronz, Roscelese, Rowlaj01, RoyBoy, Rsrikanth05, Rudjek, Ryan Postlethwaite, RyanCross, Ryanminier, Ryoutou, Ryuken14, SJP, SWAdair, Sadi Carnot, Salsa Shark, Sam Hocevar,Samboy, Sanchom, Sango123, Sankalpdravid, Saperaud, Sat84, Satori Son, Savidan, Scarian, Scerri, Sch00l3r, Schneelocke, Schoen, Schzmo, Scientizzle, Sean Whitton, SeanMack,Secretlondon, Segalsegal, Selket, Semper discens, Sergeibernstein, SeventyThree, Shalmanese, Shanes, Shawnhath, ShayneRyan, Shellreef, Shizhao, Shoessss, Shpakovich, Shrikethestalker,Sifaka, Sillyboy67, Sionus, Skatebiker, Sl, Slash, Smack, Smartweb, Smurrayinchester, Snoyes, SoSaysChappy, Someone else, SparrowsWing, SpeedyGonsales, SpookyMulder, SpuriousQ,Squadoosh, SquirrelMonkeySpiderFace, Srnec, Stan Shebs, Stassats, StaticVision, Stefan, Stephan Leeds, Stephenb, Stone, Stormie, Strongbadmanofme, StuFifeScotland, Suidafrikaan, Suisui,Sunborn, Superjustinbros., Supertigerman, Superworms, Supia, Suuperturtle, Sweetness46, TMC, Tarantola, Taras, Tarquin, Taylor4452, Techdawg667, Template namespace initialisation script,Tempnegro, Tempodivalse, Tempshill, Terfili, TerraFrost, TestPilot, Tetracube, Texture, Tf1321, The Anome, The High Fin Sperm Whale, The Thing That Should Not Be, The spesh man, Theundertow, The way, the truth, and the light, TheRanger, TheSickBehemoth, 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Arnfjörð Bjarmason, 2125 ,ܩܐܪܝܥ anonymous edits

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Element  Source: http://en.wikipedia.org/w/index.php?oldid=381674113  Contributors: 1266asdsdjapg, 13lade94, 4twenty42o, 555zozo555, ABF, Academic Challenger, Aclwon, Acroterion, Adsfkl236io54lklk, Ahoerstemeier, Ajh16, Alansohn, Alchemy pete, Alison, Alsandro, Alvis, Andre Engels, Andrejj, Andres, Andy120290, Anoop.m, Antandrus, Archivist, Aremith, AxelBoldt, Ayla, Azim5498, Bantman, Beetstra, Benbest, Bender235, Benoni, Bensaccount, Bevo, Bfigura's puppy, Bhujerban, Billiards, Bir el Arweh, Blade Hirato, Blankfaze, BlueEarth, Blueboy96, Bobo192, Bogey97, Boing! said Zebedee, Bomac, Bonaparte, Bongwarrior, Bookofjude, Booshank, Brainmuncher, Brighterorange, Bryan Derksen, Brythain, Buccaneerande, Buckeyenaaashun, Burntsauce, CDN99, Cacycle, Caknuck, Caltas, Can't sleep, clown will eat me, Canada Jack, Capricorn42, CarbonCopy, CardinalDan, Cbrown1023, Centrx, Challengedgenius, CharlesC, ChemGardener, Chemeditor, CherryT, Christian75, Christopher Parham, Chun-hian, Civil Engineer III, Clutchmetal, Cmdrjameson, Commit charge, Conversion script, Css, Cynicism addict, DARTH SIDIOUS 2, Da monster under your bed, Danshil, Daracul, Darth Panda, Daydreammbeliever15, Daz643, Delldot, Demmy100, DerHexer, Discospinster, DocWatson42, Dominicp2007, Donarreiskoffer, Dor Cohen, Doulos Christos, Dozenist, Dreamer.redeemer, Drjezza, E rulez, ERK, Ebeisher, Edgar181, Edmund372, Eeekster, Effeietsanders, Elassint, Element16, ElmentPT, Epbr123, Eric119, Ericlaermans, Erik9, Euchiasmus, EugeneZelenko, Evercat, Everyking, FT2, Farosdaughter, Femto, FiP, Fieldday-sunday, Firsfron, Firzen the Great, Flewis, Franman3024, Fredrik, FunPika, Funnybunny, Fusion Power, FutharkRed, Gail, GangofOne, Gary Levell, Gdo01, Gene Nygaard, Gentgeen, Geraki, Giftlite, Gilliam, Glenn, Glennklockwood, Gogo Dodo, Good Olfactory, GoodDamon, Googleguy1234, Grafen, Graham87, Grahamching, Greasel5, Grim23, Guoguo12, Gwern, Gwernol, HalfShadow, Hamsterlopithecus, Hawaiian717, Hda3ku, Headbomb, HedgeHog, Helenginn, Heron, Het, Hexii, Hi ruwen, Hostel369, Hvn0413, Hydrogen Iodide, IRP, Icairns, Imnotminkus, Into The Fray, Ionescuac, Iridescent, Ismaeelah, Isogolem, Istartfires, Itub, Ixfd64, J.delanoy, J8079s, JDspeeder1, JForget, Jagged 85, Jamesofur, Jaw959, Jay, Jeff G., Jermentr, JerrySteal, Jhbdel, Jimduck, John, Johnpseudo, Johnuniq, Jojit fb, Joseph Solis in Australia, Jrockley, Julian Mendez, Karlengblom, Karlhahn, Karol Langner, Katieh5584, Kay Dekker, Keilana, King of Hearts, Kingpin13, Kinu, Kipala, Kiran201193, Klemox, Korg, Kosebamse, KrakatoaKatie, Kristbg, Kungfuadam, Kuratowski's Ghost, Kurykh, Kushboy, L Kensington, LFaraone, La Pianista, Lahiru k, Lala2034, LarryMorseDCOhio, Laurascudder,

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LeaveSleaves, Les boys, Lightmouse, Lindmere, Loa, Lordaraq, Lordshaun, Lradrama, Luk, MER-C, MK8, Machine Elf 1735, Madris, Maksim L., Man vyi, Mani1, Maralia, Marek69,Martin451, Materialscientist, Matwilko, Mav, MaxSem, Maxkirk1, Mboverload, McPoopyPee, Melchoir, Menchi, Mercury610, Merovingian, Metrax, Mexistache, Michele600, Michelle192837,Mikespedia, Minesweeper, Miquonranger03, MisterSheik, Mitchellpuss, Mjkhfg, Moda yahia, Moni3, Moocow121, Morgana The Argent, Mpb4lol, Mr.pomo, Mulad, Mwanner, Mxn,Mydoghasworms, NSR, Nakon, Nakumi, NawlinWiki, Nemesis of Reason, Nergaal, Neurolysis, Newportm, Nick C, Nick Y., NickW557, Nietzscheanlie, Nilfanion, Nirmos, Nivix, Nmacu,NoPity2, Nousakan, Nsaa, Nurg, Nvj, Obradovic Goran, Obrian7, Oda Mari, Onceonthisisland, Orbis 3, OwenX, Oxymoron83, Paleorthid, Patrick, Pax:Vobiscum, Pcfjr9, Persian Poet Gal, Peter,Peter Delmonte, PeterisP, Phantomsteve, Pharaoh of the Wizards, Phazvmk, Physchim62, Piano non troppo, Pinethicket, Pingveno, Pj13, PleasantPheasant, Polyparadigm, PrestonH, PrincealiG,Proofreader77, Prowster, PseudoOne, PxT, Qst, Quintusdecimus, R'n'B, R. fiend, RJHall, RJav, RMFan1, RTC, RadioKirk, Ranveig, Rathla, Raven4x4x, RedHillian, Reddi, Res2216firestar,Rettetast, Riana, Rich Farmbrough, Rickterp, Rifleman 82, Rjwilmsi, Rmhermen, RobertG, Rodhullandemu, Roentgenium111, Roftltime8, Romanm, Romit3, Roscoe x, RoyBoy, Rpr117,Rpyle731, Rrburke, Rursus, Ryoung122, SNPP, Sadi Carnot, SallyForth123, Saperaud, Sarc37, Sbharris, SchfiftyThree, Schneelocke, ScottDavis, ScottJ, Scream1013, Sedsa1, Sengkang, Shanes,Shanoor212, Shoeofdeath, Sionus, Sir Nicholas de Mimsy-Porpington, Sjn28, Skatebiker, Skomorokh, Smalljim, Snailwalker, Sobolewski, SpeedyGonsales, SpookyMulder, Steel, Stevertigo,Stone, Strait, Suisui, Sumo su, SusanLesch, Susiban227, Svlad Jelly, Syncategoremata, Synchronism, T55648L, THEN WHO WAS PHONE?, TJDay, TStein, Tanaats, Tangotango, Tarquin,Taxman, TekNOSX, Teleomatic, TenOfAllTrades, Terence, Texture, The Anome, The Original Wildbear, The Thing That Should Not Be, The Utahraptor, TheRanger, Thibbs, Thincat, Thingg,Thryduulf, Thue, Tide rolls, Timir2, Tiptoety, Toddst1, Tom harrison, Tombomp, Tony Corsini, Trevor MacInnis, Trusilver, Trygve94, Useight, Van helsing, Vianello, Vicki Rosenzweig,Viskonsas, VogonFord, Vsmith, Walkerma, Warut, Wavelength, Wayward, Werdna, WhatamIdoing, Whisky drinker, White Cat, Wik1ped1a is meant 2 be vanda1ised, William Avery, Wimt,Winchelsea, Winick88, Wolfrock, Wuhwuzdat, Xenon54, Xerxes314, Xevi, Xiahou, Yakudza, Yamaguchi先生, Yamamoto Ichiro, Yelyos, Yidisheryid, Youssefsan, Zbisasimone, ZeekyH.bomb,ZooFari, Александър, 1028 ,لیقع فشاک anonymous edits

Isotope  Source: http://en.wikipedia.org/w/index.php?oldid=382156045  Contributors: -jmac-, 7, A purple wikiuser, A3RO, AVand, AcroX, Adashiel, Addshore, AdjustShift, Adrian.benko,Afirtree, Ahoerstemeier, Alan Peakall, Alansohn, Alex2009258, AlexiusHoratius, Alpine McRiper, Andres, Angel crystal88, Animum, Ansonchen88, Antandrus, Apbiologyrocks, ArglebargleIV,Arnd Klotz, Ashiel7, AssistantX, AstroNomer, Astronaut, Atif.t2, BLP-outrageous move logs, Badgernet, BaseballDetective, Bensaccount, BigFatBuddha, BillyZane, Bkell, Black Falcon,Bluemask, Bobo192, Bongwarrior, BoomerAB, Bovlb, Bratsche, BrianScanlan, Bryan Derksen, C.Fred, CDN99, CTZMSC3, Cadaeib, Caltas, Camw, CanadianLinuxUser, Capricorn42, Cassivs,Catgut, Cburnett, Ceranthor, Charles Clark, Charlesdrakew, Cheif Captain, Chick Bowen, Christopherlin, Chuchunezumi, Chzz, Citynoise, Cjthellama, Ckatz, Clemmy, Clicketyclack, Cmichael,Colinho22, Conversion script, Cookiedog, Cosmo737, Courcelles, Crazy Boris with a red beard, Cryptic, D.H, DMacks, DV8 2XL, DagnyB, Daniel Olsen, DanielCD, Davecrosby uk, Davewild,Dcooper, Dcrunner, Deor, DerHexer, Deryck Chan, Dirac66, Discospinster, Dooky, Dougz1, Dricherby, Drphilharmonic, Dusti, Dysprosia, Długosz, E Wing, EdTrist, Edgar181, Elockid,Epbr123, Erik9, EscapingLife, FadieZ, Fastily, Father McKenzie, Femto, Fetchcomms, Feydey, Fieldday-sunday, FlyingToaster, FocalPoint, Fumitol, G716, GB fan, GRider, GangofOne, GaryKing, Gbyers72, Giftlite, Gilliam, Gimmetrow, Glenn, Gmaxwell, Godwotan, Graham87, Greatspacegibbon, Greenpuppy333, Gryphn, Guanaco, Gurch, Gurps npc, HOUZI, HPaul, Hadal,Haidata, Hakkahakkabazoom, HalfShadow, Hans Moravec, Headbomb, Hectorthebat, Heliomance, Hello Control, Hey jude, don't let me down, Howy9814, Hplommer, Hsheller, IRP, IW.HG,Icairns, Icorrectu, Indon, Interwal, Iridescent, Itub, Ixfd64, J Di, J.delanoy, JForget, JWB, Jclemens, Jclerman, Jespinos, Jklumker, Jlking3, Jmocenigo, JoanneB, John254, Jonny.sinclair, Jons63,JuJube, Juanmantoya, Jumbuck, Junglecat, Jusdafax, Jusjih, K10wnsta, KJS77, KNewman, Kaihsu, Kaldari, Kanxkawii, Kaypoh, Kazasik.3, Kbdank71, Kdebens, Keesiewonder, Khukri, King ofHearts, Kkmurray, Ks0stm, Kurzon, Lethe, Leuko, LibLord, Liftarn, Logan, Luk, Luna Santin, MER-C, Magister Mathematicae, MagnusGallant, Makeachange10, Malo, Mani1, Manipulator,Marek69, Marj Tiefert, MarkS, Martin451, Master Jay, Master of Puppets, Mav, Megamix, Meisterkoch, Mentifisto, Merlion444, Merovingian, Mikez, Minesweeper, Minivip, Miquonranger03,Mirandamir, Mjroots, Moonriddengirl, Myanw, Myrddin1977, Mytildebang, Nakon, Nanzilla, NawlinWiki, Nehakhat, Nellyb1993, Nergaal, NewEnglandYankee, Newportm, Nibuod, Nmacu,Noctibus, Nuclearmedzors, Nuttycoconut, Oba.coskun, Obradovic Goran, Oda Mari, OwenX, Oxymoron83, Palefire, Patrick, Pbroks13, Pehsfo, Peterlin, Pgk, Phantomsteve, Philip Trueman,Phillip2, PhySusie, Physchim62, Pinethicket, Pip2andahalf, Pjvpjv, Prakharbirla, Prari, Prolog, Promethean, Proofreader77, Prosfilaes, Pyrospirit, Quantockgoblin, Quiddity, Quilbert, Qxz,Radagast83, Rainmonger, Rambam rashi, Ray23713111, RedRollerskate, Richard D. LeCour, Rjwilmsi, Rod57, Ronhjones, Ryanrulz 11, Ryulong, SCEhardt, SH84, SaltyBoatr, Sam Li,SamMichaels, Sami Lab, Satori Son, Sbharris, ScienceApologist, Sean.hoyland, Semperf, Senator Palpatine, Shantavira, Sharkface217, Shellreef, Shoopmawhoop, Shotime900, Shyamal, Sidhughanta, Silvem, Silverchemist, Sin-man, SkerHawx, Skippydogue, Slysplace, Smack, Smith609, SmokeyJoe, Snigbrook, Snoyes, Spiff, Spitfire, St00j, Stemonitis, Stephen Luce, Stephenb,Stokerm, Strait, StuFifeScotland, Suisui, SunCreator, Sunray, Sw607813, TKD, Tad Lincoln, Tango, Tanthalas39, Tanweer Morshed, Tarquin, Taxman, Technopat, Thatguyflint, The Thing ThatShould Not Be, The birch tree and the dandelion, Theadder, Themole12, Theone00, Throwaway85, Thryduulf, Thwait, Tiddly Tom, Tide rolls, Tim1357, Tocharianne, Tommy2010,Transcendence, Trelvis, Twinckletoes911, Tylerni7, Ulric1313, Uncle Dick, Unvandalizor, V1adis1av, VASANTH S.N., Veneventura, Versus22, Viriditas, Viridium, Vuerqex, WFPM, WRonG,Walden, Watcharakorn, WatermelonPotion, Wavelength, Wenli, Wiki alf, Wikipe-tan, Will Beback, WilliamRoper, Willking1979, Wimt, Witchyrose, Wmahan, Wolfmankurd, Wsycng,Xerxes314, Xhaoz, Yonatan, Yuanchosaan, Z.E.R.O., Zoohouse, 943 anonymous edits

Orbital  Source: http://en.wikipedia.org/w/index.php?oldid=379221831  Contributors: 345gim, A.Z., AVand, Alansohn, Allstar86, Ambuj.Saxena, Ashmoo, Astrochemist, Audriusa, Avjoska,B7582, BRG, Baccyak4H, Bduke, BeeArkKey, Beetstra, BenB4, BenFrantzDale, Benjah-bmm27, Bomac, Bowlhover, Bth, Calvero JP, Capricorn42, Ceyockey, Chemiker, Cmdrjameson,Conversion script, Cool3, Cpl Syx, Crystal whacker, Csmallw, DMacks, Deconstructhis, Delldot, DerHexer, Deror avi, Dirac66, DivineAlpha, Djdaedalus, Djr32, Dlrohrer2003, Donarreiskoffer,EconoPhysicist, Edward, Eequor, Ehrenkater, Ekwity, Ema Zee, Enormousdude, Epbr123, Excirial, Fred Bradstadt, Fresheneesz, Fuzzform, Gentgeen, Gerbrant, Giftlite, Gil987, Gilliam, GodEmperor, Guanaco, Hairy Dude, HannesJvV, Harriv, Headbomb, Hellbus, Heron, Hiyabulldog, HolIgor, Hooperbloob, HorsePunchKid, Hugo-cs, Ian**, Into The Fray, Isaac Dupree, Isilanes,JKW, Jackol, Janek Kozicki, Jeff02, John Vandenberg, Jrockley, Karol Langner, KhemistKurt, Kungfuadam, Kurzon, Kwamikagami, L Kensington, Laburke, Lightbound, Lightmouse, LilHelpa,LtNOWIS, MER-C, MONGO, Mako098765, Mani1, Mattopia, Maurice Carbonaro, Maurreen, Mav, Michael Hardy, Monfornot, NHRHS2010, Nakon, NamfFohyr, Necessary Evil, Neonumbers,Neverquick, Nevit, Notapotato, OlEnglish, Pagw, Pascal666, Pfalstad, Plasmide911, Plotfeat, PrestonH, R'n'B, Raul654, Reelx09, RobertAustin, RogueNinja, Romanm, Ronhjones, Rotational,SDC, SUL, Sadi Carnot, Samwb123, Sbharris, Scerri, Schoen, ScienceApologist, SeventyThree, Shirik, Simstud16, Slakr, Smack, Smokyhallow, Snobscure, Stevey7788, Stismail,StradivariusTV, THEN WHO WAS PHONE?, Tarquin, Taxman, TelecomNut, Thrindel, Tim Starling, Tomas e, Tonyrex, Topbanana, Ttony21, User A1, V8rik, Vinay.bhat, Virginia friedchicken, Voyajer, Vsmith, WinterSpw, Xetrov znt, Yoshigev, 212 anonymous edits

Group  Source: http://en.wikipedia.org/w/index.php?oldid=378228595  Contributors: (jarbarf), 1297, Ace Frahm, Adams kevin, Adilch, Ahoerstemeier, Alansohn, Andrew Levine,ArnoLagrange, Axecution, AxelBoldt, Badgettrg, Beve, Bob323457364584649, CactusWriter, Canderson7, Caramdir, Cometstyles, Cosmium, Css, Ctachme, Cybercobra, DarrenHensley, Dcljr,Deeptrivia, Dirac66, Discospinster, Dlohcierekim, DragonflySixtyseven, Edgar181, Edwinstearns, El C, Elektron, Falcon8765, Farazy, Felix Wan, Femto, Filemon, Fonzy, GCarty, GeneNygaard, Gentgeen, Giftlite, HK-90, Hammer Raccoon, Hede2000, Herbee, HolIgor, Hugo-cs, Hvn0413, IRP, Ianweller, Icairns, Itub, J Milburn, J'88, Jezhotwells, John, Keilana, Kj cheetham,Laplacian, Legolost, Limideen, Luuva, MDov, Mani1, Marek69, Mathias-S, MattieTK, Michael Hardy, Mister Macbeth, MrsZanolini, Narson, Otolemur crassicaudatus, PRimaVeriTaVIV, PaulFoxworthy, Philip Trueman, Plasmic Physics, Reconsider the static, Rettetast, Rigadoun, Robin Patterson, RockMFR, Roentgenium111, Ronhjones, StaticVision, Steve Pucci, Stumps, Suisui,Tannin, The Anome, The Benefactor, The Thing That Should Not Be, Tmark111, UberScienceNerd, Uncle Milty, Unyoyega, ZJB3, Александър, आशीष भटनागर, 160 anonymous edits

Group I  Source: http://en.wikipedia.org/w/index.php?oldid=382017833  Contributors: 09phippsj, 1297, 64.26.98.xxx, AK Auto, AMK152, Academic Challenger, Achim1999, Acroterion,Addshore, Ahoerstemeier, Alansohn, Alchemist-hp, Alex43223, Alexander336, Andre Engels, AndrewWTaylor, Andy M. Wang, Angela, Anonymous Paul, Armoreno10, Ayeroxor, Ayla,Badseed, Badwolftv, Bagatelle, Bart133, Basement12, Benbest, Benjah-bmm27, Betacommand, Biker Biker, Bomac, Borek, Brockert, Brumski, Bryanw03, CSumit, CWii, Camp3rstrik3r,Candlemb, Cbrown1023, Charlie999, Cheeseman557, Chemicalinterest, Chris Dybala, Cimex, Cinderblock63, Clorox, Coffee, Colbuckshot, Conversion script, Countmippipopolous, Cpl Syx,Cruccone, DO11.10, DanDao, David Cat, Dawn Bard, Dbc334, Dcljr, Deagle AP, Derek Ross, Dittaeva, DocPhilBrown, Doulos Christos, Dozzabird, Drahgo, Dungodung, Dvratnam, EL Willy,Eddideigel, Edgar181, Edward, Edward321, El C, Eleuther, Elliott707, Emil76, Eric119, Erik9, Esrever, Excirial, Falcon8765, Feline1, Femto, Finlay McWalter, Firetrap9254, Flauto Dolce,Flewis, Fonzy, Frankenpuppy, Freakofnurture, Frozenguild, Funandtrvl, General robert e. lee II, Gentgeen, Giftlite, Ginga ninja 007, Glenn, Gman4eva, Graham87, Gtg204y, Gurch, Harp,Harryboyles, Headbomb, Hu, Hugo-cs, Hurricane111, Husayt, Hydrogen Iodide, IRP, Icairns, Ilahia, Immunize, Infrangible, IrishPete, Iskygge, Ixfd64, J.delanoy, JDDJS, Jan eissfeldt, Jauerback,Jmcferran, Joe Schmedley, John, Jonathunder, Joyous!, Jusdafax, KChiu7, Kanthoney, Kazrak, Kbh3rd, Keenan Pepper, KnowledgeOfSelf, Kosebamse, Krawi, Kurykh, LA2, LarryGilbert,Lcaa9, Lemons92, Leuko, Looxix, Lou.weird, Mac Davis, Malcolm, Malcolm Farmer, Manuel Anastácio, Marek69, Markhu, Markhurd, Materialscientist, Mattbr, Matthardingu, MattieTK, Mav,MaxSem, Mboverload, Megalodon99, Mejor Los Indios, Michael Hardy, Minimac93, Mjmcb1, Mlouns, Mpatel, Nakon, NawlinWiki, Nergaal, Neutrality, Neverquick, Nick Y., Nick911,Obliterator, Onevalefan, Oxymoron83, Partnerintime12, Paul-L, Philip Trueman, Philthecow, Phuzion, Pinethicket, Ponder, Possum, ProhibitOnions, PrometheusX303, PublicPossum, Pyrochem,Qtothec, Qxz, RIPCLB, Radon210, Rajragavan, Rambam rashi, Ravichandar84, Razorflame, Reach Out to the Truth, Remember, Rettetast, RevRagnarok, Rex the first, Rfc1394, RichFarmbrough, Rjwilmsi, Rob Hooft, Robchurch, Romanm, Ronhjones, Rory096, Rosarote elfe, Sam Li, Scerri, ShaunMacPherson, Shelter7, Sirtrebuchet, Skatebiker, Smashking77, Snowolfd4,SpaceFlight89, Spellmaster, Spinningspark, Spoon!, Squids and Chips, Stardust8212, StaticVision, Stephenb, Stone, Stowy2, Super-Magician, Tarquin, The Thing That Should Not Be,Thedjatclubrock, TheresJamInTheHills, Titus III, Tnayin, Tohd8BohaithuGh1, Tomos, Tomwalden, Tr-the-maniac, Trappleton, Tsange, Tsemii, Ummit, Velella, ViolentRager, Vsmith,Watcharakorn, Wavelength, WaysToEscape, Whosasking, Wikipedia brown, Winchelsea, Xdamr, Xentrion, YOSF0113, Yakudza, Zarius, Վազգեն, 567 anonymous edits

Group II  Source: http://en.wikipedia.org/w/index.php?oldid=375187611  Contributors: 1297, 64.26.98.xxx, Aadal, Ahoerstemeier, Alansohn, Ale jrb, Andre Engels, AndyVolykhov,Antony1103, Apollo, Babychanel, Badocter, Bennybp, Bggoldie, Bkell, BlueEarth, Bomac, Brion VIBBER, Chris Dybala, Chrislk02, Chrumps, Chukonu xbow, Chuunen Baka, Cimex,Conversion script, DO11.10, Darekun, Darnir redhat, Darth Panda, Dittaeva, Eddideigel, Edgar181, Element16, Ellywa, Eric119, Espi, Eugene van der Pijll, Falkflyer, Fastily, Feline1, Femto,Fieldday-sunday, Firas@user, Firsfron, FocalPoint, Fonzy, GDonato, Gamma, Gentgeen, Glendoremus, GoingBatty, Graham87, Hadal, Hellbus, Heron, Hugo-cs, Hydrogen Iodide, Icairns,IlGreven, Izalithium, J.delanoy, JForget, Jojhutton, Jóna Þórunn, Kesac, Khukri, Kingturtle, Laurinavicius, Longhair, Lop242438, MER-C, Mark grindell, Materialscientist, Mav, Mentifisto,Michael Hardy, MickiWiki, Mikeo, Miquonranger03, Monterey Bay, Mr Stephen, Nergaal, Noctibus, Nonagonal Spider, Omicron777, Paul-L, Raymondwinn, Regibox, Remember,Res2216firestar, Rex the first, Rfc1394, Rjd0060, Roadrunner, Romanm, Rrv1988, Scerri, Shellreef, Shinglor, Skatebiker, Smack, Soliloquial, Squids and Chips, Stone, Suisui, Synergism,Tarquin, The Thing That Should Not Be, Tide rolls, Tim1357, Timmeh, Titus III, Tom harrison, Tom.k, Ummit, Versus22, Vsmith, Weasel the spriggan, Wiki alf, Wyklety, Xerxes314, आशीषभटनागर, 265 anonymous edits

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Group III  Source: http://en.wikipedia.org/w/index.php?oldid=374797882  Contributors: Ahoerstemeier, Alchemist-hp, Angela, Arakin, Archimerged, Auric, Bomac, Brane.Blokar, EdH,Eddideigel, Edgar181, Eric119, Feline1, Femto, Firq, Fishing Chimp, Flying Jazz, Freddy S., Fvincent, Gentgeen, Heron, Hugo-cs, Icairns, Intelligentsium, Istilidion, J.delanoy, Jdrewitt,Jimfbleak, Joanjoc, King of Hearts, Malcolm Farmer, Materialscientist, Michael Hardy, Mschel, RTC, Raistuumum, Rfc1394, Rifleman 82, Scerri, The Ronin, The way, the truth, and the light,Vsmith, Wwoods, Yekrats, Zfr, 27 anonymous edits

Group IV  Source: http://en.wikipedia.org/w/index.php?oldid=380399185  Contributors: 1297, ABF, Ahoerstemeier, Alchemist-hp, Arakin, Bomac, Brane.Blokar, Chemicalinterest, Cryptic C62,Denelson83, Doprendek, Eric119, Feline1, Firq, Gaius Cornelius, Gary King, Gentgeen, Hugo-cs, Icairns, Jdrewitt, Jezhotwells, Jimp, Joanjoc, Koavf, LilHelpa, LukeSurl, Materialscientist,Nergaal, Queenmomcat, Ranveig, Rfc1394, Rjwilmsi, Rpyle731, Sander123, Scerri, Steve Pucci, Stone, TerrenceandPhillip, Titus III, Vsmith, Wikispork, Wwoods, Yekrats, 16 anonymous edits

Group V  Source: http://en.wikipedia.org/w/index.php?oldid=380401280  Contributors: Ahoerstemeier, Alchemist-hp, Amicon, Dungodung, Feline1, Firq, Gaius Cornelius, Gee Eight, Gentgeen,Hugo-cs, Icairns, Nergaal, PhilipFrampton, Ranveig, Rfc1394, SQGibbon, Scerri, Steve Pucci, Stone, Titus III, Vainamainien, VasilievVV, Vsmith, Wwoods, 18 anonymous edits

Group VI  Source: http://en.wikipedia.org/w/index.php?oldid=380406494  Contributors: Ahoerstemeier, Alchemist-hp, Banus, BillFlis, Brane.Blokar, Brockert, DavidLevinson, Eric119,Feline1, Gentgeen, Gorm, Hashar, Heron, Hugo-cs, Icairns, Lexi Marie, Nergaal, Ranveig, Rfc1394, SJP, Sabbut, Scerri, Squid661, Steve Pucci, Stone, Sugarfish, Sverigekillen, Titus III, Vsmith,Wapcaplet, Wwoods, Yekrats, Саша Стефановић, 17 anonymous edits

Group VII  Source: http://en.wikipedia.org/w/index.php?oldid=380408555  Contributors: Ahoerstemeier, Brockert, DandyDan2007, Drbreznjev, Gentgeen, Hugo-cs, Icairns, Ilyushka88,Lagatapirata, LizardWizard, Margoz, Michael Slone, Minesweeper, Nergaal, PhilipFrampton, Ranveig, Rfc1394, Scerri, Steve Pucci, Stone, Titus III, Vsmith, Wwoods, Xezbeth, 18 anonymousedits

Group VIII  Source: http://en.wikipedia.org/w/index.php?oldid=380411303  Contributors: Ahoerstemeier, Alchemist-hp, BartekChom, Booksworm, Brockert, D6, Donarreiskoffer, Firq,Gentgeen, Heron, Hugo-cs, Icairns, Narayansg, Nergaal, PigFlu Oink, Ranveig, Rfc1394, Scerri, Soman, Sss333, Steve Pucci, Stone, Titus III, Unyoyega, Vsmith, Wayland, Wwoods, Yekrats, 13anonymous edits

Group IX  Source: http://en.wikipedia.org/w/index.php?oldid=380413634  Contributors: Ahoerstemeier, Brockert, Chem-awb, Dcljr, Feline1, Firq, Gentgeen, Heron, Hugo-cs, Icairns, Mild BillHiccup, Nengli02, Nergaal, Pablo.cl, RexNL, Rfc1394, Robert Weemeyer, Scerri, Scorpion451, Steve Pucci, Stone, Tabor, Titus III, Vsmith, Wayland, Wwoods, Yekrats, 6 anonymous edits

Group X  Source: http://en.wikipedia.org/w/index.php?oldid=380415501  Contributors: Ahoerstemeier, Brockert, Btards, Chelitaannal, Chem-awb, Chemicalinterest, Dcljr, Donarreiskoffer,Femto, Firq, Gentgeen, Grm wnr, Heron, Hugo-cs, Icairns, Joanjoc, Moe Epsilon, NatureA16, Nergaal, Nk, Rfc1394, Scerri, Scorpion451, Sir Intellegence, Sss333, Steve Pucci, Stone, Titus III,Unyoyega, Vsmith, Wayland, Wwoods, Yekrats, Yono, 13 anonymous edits

Group XI  Source: http://en.wikipedia.org/w/index.php?oldid=380418286  Contributors: 1297, 193.237.249.xxx, 64.26.98.xxx, 7, Ahoerstemeier, Alchemist-hp, Alexwcovington, Bobblewik,Bobo192, Brane.Blokar, Brockert, Caesura, Chmod007, Chochopk, Chris 73, Christian75, Conversion script, Cowbert, Cthomas sysplan, Dabomb87, Den fjättrade ankan, Djavko, Edward,Elfguy, Enric Naval, Eric119, Everyking, Eweisser, Femto, Fg2, Graham87, Heron, Hick ninja, Hugo-cs, Hut 8.5, Icairns, Ike9898, IslandGyrl, Ixnayonthetimmay, Karn, Kurykh, Malbi, MildBill Hiccup, Mom2jandk, Nergaal, Neutrality, Nirvana2013, Octothorn, Oxydo, PS4FA, Pakaran, Pmanderson, Pne, Polyparadigm, PrestonH, Ranveig, Rfc1394, Rgamble, Robert Foley, RobinPatterson, SJP, Scerri, Searchme, Steve Pucci, Stone, The Anome, Titus III, Vsmith, Washerboy, Watashiwabakayo, Yekrats, Zandperl, Zoicon5, 83 anonymous edits

Group XII  Source: http://en.wikipedia.org/w/index.php?oldid=380426441  Contributors: 1297, Ahoerstemeier, Benjah-bmm27, Brockert, D6, Dabomb87, Dcljr, Femto, Gentgeen, Heron,Hugo-cs, Icairns, Jcwf, Jdrewitt, Joanjoc, Lfh, LiamE, Michael Hardy, Nergaal, Petergans, Philopp, Ranveig, Rfc1394, Roentgenium111, Ryanluck, Scerri, Steve Pucci, T-borg, Titus III, V8rik,Vsmith, Watashiwabakayo, Wayland, Wwoods, YUL89YYZ, Yekrats, 11 anonymous edits

Group XIII  Source: http://en.wikipedia.org/w/index.php?oldid=380684836  Contributors: 1297, Abshahas, Ahoerstemeier, Alex43223, Ary29, BlueEarth, Bob Saint Clar, Boothy443, Bowcekdon, Bryan Derksen, CactusWriter, Chem-awb, Chitusinha, Chris Dybala, Closedmouth, DMacks, Donarreiskoffer, Dpvwia, Eddideigel, Emperorbma, Eras-mus, Eric119, Ericxpenner, Femto,Firq, Fonzy, Freakofnurture, Gamaliel, Gene Nygaard, Gurkha711, Hadal, Hall Monitor, Hugo-cs, Icairns, Itub, Jimfbleak, Mjp797, Mxn, Nergaal, Nirmos, Ochib, Ojs, Piplicus, Rfc1394, Scerri,SchfiftyThree, Shell Kinney, Snoyes, Stone, Suriel1981, T. Anthony, Tarquin, Template namespace initialisation script, TheRanger, Titus III, Tmark111, Vsmith, Wikidenizen, Yekrats, 85anonymous edits

Group XIV  Source: http://en.wikipedia.org/w/index.php?oldid=380875889  Contributors: 1297, Ahoerstemeier, Al.locke, Alansohn, AliveFreeHappy, Bbernet13, Bkell, BlueEarth, Boothy443,Brane.Blokar, Burntsauce, Chris Dybala, Claidheamohmor, CryptoDerk, Dandelions, Darnir redhat, Dpvwia, Eddideigel, Edgar181, Eras-mus, Eric119, Femto, Fonzy, French user, GeneNygaard, Gerard1894, Gurkha711, Hairy Dude, HighKing, Hugo-cs, Icairns, Inter, Isnow, Jag123, KevinXcore, LukeSurl, Margoz, Michael Hardy, MidnightBlueMan, Nergaal, NuclearWarfare,Obliterator, Ojigiri, Philip Trueman, Puchiko, Res2216firestar, Reyk, Rfc1394, Rjwilmsi, Roentgenium111, Sapna3654, Sbyrnes321, Scerri, Scorpion451, Seano12345, Seglea, Silverxxx,Stephenb, Stone, Titus III, Tonyrex, Versus22, Vsmith, West Brom 4ever, Woohookitty, Xerxes314, Yekrats, 95 anonymous edits

Group XV  Source: http://en.wikipedia.org/w/index.php?oldid=380875622  Contributors: 1297, Afisch80, Ahoerstemeier, Ajraddatz, Altermattc, Andrea105, AngelOfSadness, Antonio Lopez,Blindman shady, Bogey97, Brane.Blokar, Butko, Chris Dybala, ChrisHodgesUK, Dpvwia, Eddideigel, Edgar181, El C, Eras-mus, Feline1, Femto, GCarty, Giftlite, Gogo Dodo, Gracenotes,H-Vergilius, Heron, Hugo-cs, Icairns, Isnow, Iwoelbern, J.delanoy, Jaknouse, Jimfbleak, Joseph Solis in Australia, Keenan Pepper, Kku, Laurinavicius, Melchoir, MichaelOReilly, Mr.Z-man, NGaG3, Nergaal, Neverquick, NewEnglandYankee, Physchim62, Ploober33, Ranveig, Rfc1394, Rmhermen, Rod57, Sbyrnes321, Scerri, Scorpion451, Stone, ThingoeCRB, Tim Ross, Titus III,Trivial, Uusitunnus, VSimonian, Vsmith, Weasel the spriggan, Xerxes314, 75 anonymous edits

Group XVI  Source: http://en.wikipedia.org/w/index.php?oldid=375188816  Contributors: 1266asdsdjapg, Ahoerstemeier, Barticus88, Brianski, Bryan Derksen, Cacycle, Conversion script,CryptoDerk, Ctachme, D-rew, DRE, DRLB, Diagonalfish, Dominus, Donarreiskoffer, Dude20202020202020, ESnyder2, Eddideigel, Edgar181, Eequor, Eleassar, Epbr123, Eras-mus, Eric119,EscapingLife, Evercat, Femto, Fuzzyeric, Gene Nygaard, Gentgeen, Geoking66, Georgia guy, Giftlite, Gorm, Gothmog.es, Gritchka, H Padleckas, HarmonicSphere, Hike395, Hugo-cs, Icairns,Imphras Heltharn, Ithunn, Jomegat, Jonel, Keenan Pepper, Kjkolb, Korath, Kwamikagami, Magnus Manske, Materialscientist, Mav, Maymay, Melaen, Nergaal, Orlica, Pencil Pusher, Rfc1394,ScAvenger, Scerri, SchfiftyThree, Siddhant, Sl, Slechte124, Smokefoot, Stephen MUFC, Stone, T.vanschaik, THEN WHO WAS PHONE?, Tarquin, The Anome, The Thing That Should Not Be,TheStarman, Titus III, V8rik, Vsmith, Wickey-nl, Wknight94, Xerxes314, Yekrats, 80 anonymous edits

Group XVII  Source: http://en.wikipedia.org/w/index.php?oldid=380483507  Contributors: 1297, 4, 7, 8thstar, APC, Aadgray, Abeg92, Addshore, AdjustShift, Ahoerstemeier, Al Silonov,Alansohn, Andre Engels, Anna Lincoln, Anonymous anonymous, Aremith, Ariel., Atlant, Badocter, Balloonguy, BaseballDetective, Bcai388, Benjah-bmm27, Bgold4, Blackcats, Blackjack48,Blue520, Bojangleskelly, Bombhead, Bongwarrior, Bovineone, Brett leigh dicks, Buttered Bread, C.R.Selvakumar, Caesura, Caltrop, Calum-11, Camoflauge, Camw, Canderson7, Capricorn42,CaptainVindaloo, Causesobad, Ceyockey, Chris Dybala, ChrisHamburg, Chrislk02, Christian75, Clarince63, Conversion script, Cosmo0, D.M.N., DMacks, DaMoose, Dajhorn, Daniel5127,Danielj123, Darklord517, David.Monniaux, Deor, Dglosser, Dhall27, Dicklyon, Dirkbb, Dlohcierekim, Dogposter, Dominic Hardstaff, Doseiai2, Driedshroom, Drumguy8800, Dungodung,Dysprosia, Eddideigel, Edgar181, El C, Epbr123, Eric119, Erutuon, Excirial, Feline1, Femto, Flameeyes, FocalPoint, Frankenpuppy, Fusionmix, Gene Nygaard, Gentgeen, Geoking66, Giftlite,Gilliam, Glenn, GoTeamVenture, Gruzd, Gtman, Guybrush, Happysailor, Harrylewis101, Hdt83, HeartofaDog, Hellbus, HenryLi, HereToHelp, Heron, HokieJC, Horselover Frost, I own in thebed, Icairns, IiizTheWiikiNerd, Imphras Heltharn, Inner Earth, Ispy1981, It Is Me Here, Itub, J.delanoy, JCraw, JForget, JMS Old Al, JRM, Jab843, James.Spudeman, JamesBWatson, Jebba,Jeffq, Jennavecia, Jeronimo, Jfurr1981, Johnleemk, Jomasecu, Jorge Stolfi, Josh Grosse, Jujutacular, Julesd, Karenjc, Kcandnikko7, Killua98 killer, Knowhow, KnowledgeOfSelf, Kotiwalo,Kukini, LMB, La goutte de pluie, Latka, Lightdarkness, Limideen, Lockesdonkey, Lop242438, Lumos3, MER-C, Madhero88, Malcolm Farmer, Mani1, Marx01, Materialscientist, Mattylak,Mav, Meisterkoch, Memodude, Mendaliv, Messageman3, Mgiganteus1, Midnightblue94tg, Mikespedia, MindstormsKid, Muzekal Mike, Mxn, NathanHurst, NatureA16, Naught101,NawlinWiki, Nergaal, Nick C, Nick Y., Ninly, Nlu, No Guru, Noctibus, Nscheffey, Nubiatech, OldakQuill, Oxymoron83, P1415926535, PanagosTheOther, Paul-L, Pb30, Peter.C, Physchim62,Piano non troppo, Pinethicket, Piza pokr, Pko, Plumbago, Postlewaight, Praefectorian, RECTUM INSPECTUM, RJHall, RL0919, Raerae11, Raerae123, RandomStringOfCharacters, RayAYang,RedAndr, Regardless143, Remember, Rfc1394, Roentgenium111, Rror, Russoc4, Scerri, SemperBlotto, Shootbamboo, Skraz, Sky Attacker, Sole Soul, Someguy1221, Squids and Chips,Stevey7788, Stone, Sturm55, Suisui, Sven87, T-borg, Tarquin, Taxman, Tcncv, Teh Ploxanater, Terra Xin, The High Fin Sperm Whale, The Thing That Should Not Be, Tide rolls, Tim Goodwyn,Timwi, Titoxd, Titus III, Tommo65, Tommy2010, Topbanana, Tssa 893, Venu62, Versus22, Vonlich, Vortexrealm, Vsmith, Wavelength, Wayward, Wceom, Welsh, Wickey-nl, Wifione, WildWizard, William Avery, Willking1979, Woohookitty, Zbvhs, Þjóðólfr, Александър, 604 anonymous edits

Group XVIII  Source: http://en.wikipedia.org/w/index.php?oldid=381911450  Contributors: Abe Chal!, Falcon8765, Nergaal, Owenozier, Pacdude9, Philip Trueman, Roentgenium111,Scientific29, The Anome, Tphi, 6 anonymous edits

Period  Source: http://en.wikipedia.org/w/index.php?oldid=377092824  Contributors: 1297, Adilch, Ahoerstemeier, Alansohn, Bethastrong, Brane.Blokar, Ctachme, Dcljr, Feline1, Fremsley,Gentgeen, Golfandme, HexaChord, IRP, Icairns, Jakwra, Jared999, Jimbuckar00, Jusjih, Kandar, Kayau, Keilana, Kungfuadam, Kwamikagami, Laurinavicius, Legolost, Luuva, M412k, Mav,Ms2ger, N2e, Noobatron30, Northumbrian, Plainandsimple, Pstuart, Qxz, R'n'B, Rdx-77, Rifleman 82, Rigadoun, RockMFR, Ronhjones, Suisui, Tckma, The Anome, VMS Mosaic, Wikijens,Xnybre, Yankeesrule3, Yekrats, Александър, आशीष भटनागर, 101 anonymous edits

Page 160: Periodic Table

Article Sources and Contributors 157

Pediod 1  Source: http://en.wikipedia.org/w/index.php?oldid=375154463  Contributors: 1297, AMK152, Aezram, Ahoerstemeier, Chris 73, Dzubint, Eddideigel, Edwinstearns, Ellywa, EscapeArtist Swyer, Feline1, Ferengi, Gary King, Hashar, IW.HG, Itub, K2dawest, Koavf, Kwamikagami, Magnus Manske, Marc Tobias Wenzel, Materialscientist, Mike Rosoft, Mr Stephen, Ms2ger,Nergaal, Plasticup, RedHillian, Reywas92, Rfc1394, SiriusAlphaCMa, Suisui, Tony Sidaway, 19 anonymous edits

Extensions  Source: http://en.wikipedia.org/w/index.php?oldid=379435876  Contributors: 09curranm, 4, AED, Ahoerstemeier, Alakasam, Alinor, AndrooUK, Bduke, Bkell, BlueEarth,Brane.Blokar, Bryan Derksen, Choihei, Cowplopmorris, DMacks, DanielDeibler, Dcljr, Dixongrove, Donarreiskoffer, Droog Andrey, Eddideigel, Efficiency1101e, Ehrenkater, Feline1, Femto,Finalius, Flyguy649, Fonzy, Gershwinrb, Glenn L, Gurch, Headbomb, INVERTED, Icairns, Ionutzmovie, Iv0202, Jkj115, Keenan Pepper, Koavf, Kolo-Dearney, Kruckenberg.1, Kubigula,Kwamikagami, LittleDan, Luna Santin, MTM, Mandarax, Mav, Mikespedia, Ospalh, Oxymoron83, Ozabluda, Patriot8790, Pauli133, Petergans, Phe, Pne, Psychonaut, R'n'B, Rfc1394, RichardArthur Norton (1958- ), Rihanij, Robo37, RockMFR, Roentgenium111, Sbyrnes321, Smack, Swpb, Tarquin, Tetracube, Tpbradbury, Unbitwise, UnitedStatesian, Vartan84, Vuerqex,Yankeesrule3, Yinweichen, 155 anonymous edits

Block  Source: http://en.wikipedia.org/w/index.php?oldid=379071790  Contributors: Ahoerstemeier, Brane.Blokar, Bth, Butros, Cantor, CardinalDan, Cosmium, Ctachme, DMacks,EamonnPKeane, Emperorbma, Gentgeen, Höyhens, IvanLanin, J'88, Looxix, Mav, N2e, Numbo3, Pjstewart, Rich Farmbrough, SimonMayer, Smack, Sombrero, Suisui, Tarquin, The Anome,Urod, WFPM, Yankeesrule3, आशीष भटनागर, 19 anonymous edits

s-block  Source: http://en.wikipedia.org/w/index.php?oldid=380133449  Contributors: Ahoerstemeier, Balcer, Betterusername, Brane.Blokar, Bryan Derksen, Choihei, Dcljr, Donarreiskoffer,Elonka, Femto, Flying Jazz, Fonzy, Fuhghettaboutit, Gentgeen, Giftlite, Green caterpillar, Gurch, Hairy Dude, Hugo-cs, Icairns, Jh12, Kungfuadam, Mav, Mintleaf, Nabla, Nergaal, Phe, Piperh,Pro.in.vbdnf, Rfc1394, Rjelves, Salsa Shark, Shellreef, Smack, SuperDT, Tarquin, Zeimusu, 36 anonymous edits

p-block  Source: http://en.wikipedia.org/w/index.php?oldid=380843243  Contributors: Ahoerstemeier, Amy6126, AnnaJGrant, Anoop.m, Balcer, Bowcek don, Brane.Blokar, Bryan Derksen,Choihei, Dak0728, Dcljr, Donarreiskoffer, Eddideigel, Femto, Flying Jazz, Fonzy, Gentgeen, Hugo-cs, Icairns, JonLS, Knuckles, Mav, Modeha, PamD, Phe, Qvvx, Rfc1394, Rich Farmbrough,Shellreef, Smack, Stefano85, Stone, 26 anonymous edits

d-block  Source: http://en.wikipedia.org/w/index.php?oldid=380844645  Contributors: Ahoerstemeier, AlmanacManiac, Balcer, Brockert, Bryan Derksen, Copperdrake, Dcljr, Deltopia, Dirac66,Divide, Dodo bird, Donarreiskoffer, Eddideigel, Feline1, Femto, Flying Jazz, Fonzy, Gail, Gentgeen, GeoffMacartney, Gogo Dodo, Icairns, Jdrewitt, Jnothman, Jrok311, Knuckles, Lfh, Mav,Menchi, Merovingian, Modeha, Nergaal, Nick, OlEnglish, Phe, Rfc1394, Rogerb67, Shellreef, Simon the Likable, Smack, Sombrero, SusanLarson, Tarif Ezaz, Tlevine, Torika, Welsh,Wikien2009, Zeugma21, 60 anonymous edits

f-block  Source: http://en.wikipedia.org/w/index.php?oldid=382160280  Contributors: Ahoerstemeier, Balcer, Brane.Blokar, Bryan Derksen, Burubuz, CTZMSC3, Chrylis, DMacks, Dcljr,Donarreiskoffer, Dureo, Epbr123, Femto, Fonzy, Gentgeen, Givesnake79, Hugo-cs, Icairns, IceUnshattered, Imphras Heltharn, Jmendii, Knuckles, LedgendGamer, Malbi, Mav, Modeha, Nergaal,Paul A, Petergans, Phe, Pjstewart, Rfc1394, Shellreef, Smack, 40 anonymous edits

Actinide  Source: http://en.wikipedia.org/w/index.php?oldid=381524670  Contributors: 4, Aelffin, Ahoerstemeier, Akadruid, Alexf, Andre Engels, Antandrus, Badocter, Barticus88, Beland,Burubuz, Camw, Can't sleep, clown will eat me, ChongDae, Chris the speller, Cjthellama, Conversion script, Cyrius, David Gerard, Davidryan168, Deglr6328, Derek Ross, Dicklyon, Dmn,DuncanHill, Ebe123, Eddideigel, Ehrenkater, Etincelles, Excirial, Feline1, Femto, Finalius, Flying Jazz, FourBlades, Fred Bauder, Fredrik, Gentgeen, Geraki, Glenn4pr, Hairy Dude,Hammer1980, HarDNox, Hashar, Hede2000, Herbee, Hugger666, Icairns, JWB, JaGa, Jdrewitt, Jet57, Jet66, Jhd, Johnleemk, Jrockley, Keenan Pepper, LOLthulu, Levil, Little Mountain 5,Looxix, Lstanley1979, Lucent, MagnaGraecia, MarsJenkar, Materialscientist, Mfearby, Myshare, Nergaal, Njaard, Old Moonraker, Ospalh, Petergans, Pjstewart, Pstudier, Remember, Rfc1394,Rich Farmbrough, Ricknightcrawler, Rifleman 82, Rotten, Rursus, Shalom Yechiel, Sl, Speciman00, SpookyMulder, Squids and Chips, Stephen C. Carlson, StephenBuxton, Stone, Supremevo01,Szaszicska, TarmoK, Tarquin, TheVault, TrygveFlathen, Tygrrr, Vicki Rosenzweig, Vsmith, Whiner01, Wimt, Wknight94, Zereshk, Zfr, Ztobor, आशीष भटनागर, 107 anonymous edits

Lanthanide  Source: http://en.wikipedia.org/w/index.php?oldid=381697846  Contributors: 129.128.164.xxx, 157.138.10.xxx, 2over0, Ahoerstemeier, Als6tt, Andkn, Andre Engels, Andrewa,Antonio Lopez, Barticus88, Ben-Zin, Benbest, Beryllium-9, Burubuz, ChongDae, Christian75, Chuck Carroll, Consumed Crustacean, Conversion script, Coppertwig, Cyktsui, DaGizza, DeryckChan, Dirac66, Dittaeva, Dmn, Docboat, Doenut1793, Doniago, Doulos Christos, Dr.sparkle, Eddideigel, El C, Epbr123, Eroica, Exodio, Feline1, Femto, Flying Jazz, Fred Bauder, Gentgeen,Ghewgill, Gro-Tsen, Hairy Dude, Hede2000, Herbee, Hydrogen Iodide, Iammeheremeroar, IanKDavis, Icairns, Ideyal, Imphras Heltharn, JaGa, Jamesday, Jbp3, Jdrewitt, Jedibob5, Jet57,Johantheghost, Joriki, Karelj, Kate, Levil, Lfh, Looxix, MSWilson, Materialscientist, Mav, Michbich, Mr webby, Mr.Z-man, Myshare, NawlinWiki, Pejman47, Petergans, PierreAbbat, Quiddity,Raymondwinn, Remember, Rfc1394, Rgu.bhagyamma, Romanm, Royboycrashfan, Sander123, Sbyrnes321, Shinkolobwe, Sl, Smithbrenon, Sparks1080, Stismail, Stone, Supremevo01,Synchronism, Tarquin, Tensorpudding, Tetracube, Trapolator, V1adis1av, V8rik, Walkerma, Wasell, Wavelength, William Avery, Yekrats, 135 anonymous edits

Metal  Source: http://en.wikipedia.org/w/index.php?oldid=382124192  Contributors: 07andy07, 123theman123, 12dstring, 2D, 4twenty42o, 56, A Macedonian, A Red Pirate, A Softer Answer, Ab, A3RO, ACSE, ARUNKUMAR P.R, Abrech, Ace Frahm, Adambro, Aetylus, [email protected], Ahoerstemeier, Aitias, AlanD, Alansohn, Alaphent, Albert galiza, Ale jrb, Alex.muller,Alexius08, Alexostamp, Alfio, Alisterg, Allstarecho, Amorymeltzer, Andonic, Andres, AndrewWTaylor, Andrewpmk, AndriusG, Andy M. Wang, Anonymous Dissident, Antandrus,Anthony197427, Anville, Anwar saadat, ArielGold, Arnon Chaffin, Ascidian, Ashanda, AshidoX, Ashill, Astavats, AstroNomer, AtaruMoroboshi, Averizi, Avicennasis, Avnjay, Awickert, Axlq,Ayla, Back and Forth, Badgernet, Barticus88, Beaumont, Belinrahs, Bensaccount, Bfigura's puppy, Big Bird, Bill K, Billde, Bird747, BladeHamilton, BlnLiCr, BlueEarth, Bobbychong, Bobo192,Boccobrock, Bogey97, Bonadea, Bongwarrior, Borne nocker, Bornhj, BradBeattie, Bryan Derksen, Brysonlochte, Bubonic plague, Buxbaum666, CIreland, CUSENZA Mario, Cacycle, Caffm8,Callumpuffy, Calvin 1998, CambridgeBayWeather, Can't sleep, clown will eat me, Canderson7, Capricorn42, Carlmalone, Centrx, Cgingold, CharlotteWebb, Chipthief00, Chris Markides, Christhe speller, Christian List, Christian75, Ck lostsword, Ckatz, Closedmouth, Cmichael, Cobi, Cometstyles, Conversion script, CosineKitty, CrazyChemGuy, Cremepuff222, Crucis, Cst17, Curps,Curt5876, Cwenger, Danceangle90, Danski14, Dark Master87, Darkrangerj, Darrendeng, David Gale, Dawn Bard, DeadEyeArrow, Deamon138, Denali134, Deor, DerHexer, Dik, Dina,Discospinster, Divyansh.ip15, Dlae, Docboat, DoubleBlue, Dr. Beaster, Dspradau, Dysepsion, E rulez, EBY3221, ERcheck, Eaolson, EdGl, EdH, Edgar181, Edward321, Ekilfeather, El C,Elaragirl, Element16, Elen of the Roads, Elfguy, EmoCon, Emperorbma, Englishnerd, Epbr123, Erdal Ronahi, Esanchez7587, EurekaLott, Everyking, Excirial, FF2010, Face-2-face,Faithlessthewonderboy, Farosdaughter, Fddf, Felix Folio Secundus, Femto, Fieldday-sunday, FinalRapture, Fir0002, Flewis, Flying Jazz, FlyingToaster, Fossiliferous, Fox, Fram, Fran Rogers,Frankenpuppy, Franksbnetwork, Fransvannes, Fratrep, Frazzydee, Frehley, FreplySpang, Gadfium, Galoubet, Gamunday, Garion96, Gazza BWFC, Geminiey, Gentgeen, George bennett, Ghaly,Giftlite, Gilliam, GinaDana, Glane23, GlassFET, Glen, Graeme Bartlett, Graibeard, Graysen98, Gromlakh, Guitardemon666, Gundampilotspaz, Gurch, Gwernol, Gökhan, HANZBLIX, Hadal,HaeB, Haham hanuka, Hallenrm, Hamsterlopithecus, HappyCamper, Harald Hansen, Hardness, Hardymahi, Headsets, Hellboy2hell, Hello108, Hephaestus III, Heron, Hilts99, I am grate,ILike2BeAnonymous, INVERTED, Iain99, Ian13, Icairns, IceDragon64, Icseaturtles, Im anoob68, Imaprincezz, ImperatorExercitus, Improbcat, Inhumer, InvertRect, Iothiania, Iridescent, Ixfd64,J-t-m, J.delanoy, JDspeeder1, JForget, JaGa, Jackol, Jacob.jose, Jaenop, JakeHawley, Jaknouse, James A. Stewart, James086, Jamesofur, Jamesontai, Jan.Smolik, Janet Davis, Jaranda, JayHenry,Jcwf, Jeepday, Jennavecia, JimVC3, Joe056, JoeGucciardi, Joeyrockyhorror, John, John of Reading, Johnleemk, Jojit fb, Jonathanr668, Joostvandeputte, Jose77, JoshuaZ, Jredmond, Jtir,Jujutacular, Juliancolton, Juliantwd, Juliemfreeman1, Jusdafax, Jusjih, K Fuchs 45784578, Kaiba, Katalaveno, Katoa, Ken g6, Ketsuekigata, Kevin, Kingpin13, KnowledgeOfSelf, Kukini,Kungfuadam, L33th4x0rguy, L7tr4h, La goutte de pluie, Landon1980, Latics, Latitude0116, Latka, Lectonar, Leeman056, Lights, Limmy11frog, Limonns, LizardJr8, Logger9, Longstead,LouScheffer, LovesMacs, Lowellian, Luk, Luna Santin, Luuva, Lypheklub, MC10, MER-C, MONGO, Magister Mathematicae, Mahahahaneapneap, Malafaya, Man vyi, Mandarax, Mangostar,MansonScar, Marek69, MarkGallagher, MarsRover, MatTticus, Materialscientist, Mattinbgn, Maurreen, Mcwatson, Meekywiki, Megaboz, Mejor Los Indios, Mentifisto, Mermaid from the BalticSea, Metalbul, Michal Nebyla, Mikaey, Mikenorton, Mmxx, Modernist, Monorailx, Mouvement, Mr Stephen, Mtd2006, Muéro, Myanw, Mysdaao, N5iln, NHJG2, Nagy, Nakon, Narayansg,NawlinWiki, Nayvik, Nbarth, Nburden, Ndenison, Neo001, NerdyNSK, Nergaal, Nevit, NewEnglandYankee, Nick, NickW557, Nihiltres, Nirvana2013, Nivix, Njaelkies Lea, Nology,Notmattepp, Nub22, Nuggetboy, Numbo3, Nwbeeson, ObeyMe, Oiws, Onebravemonkey, Oroso, Ortolan88, Ottawa4ever, OwenX, Oxymoron83, P4k, Papa November, Paramaya, ParticleMan,Passw0rd, Paul August, Pavel Vozenilek, Pbrower2a, Pepper, Persian Poet Gal, PeterWiki09, Philip Trueman, Phoebe, Piano non troppo, Pilotguy, Pinethicket, Pink!Teen, Pip2andahalf, Pne,Pokemonned, Pol098, Polartsang, Pomlikespee, Poor Yorick, Possum, Prashanthns, Press-yes, PrometheusDesmotes, Pxlnight13, Q43, Qxz, RJHall, RL0919, Radon210, RainbowOfLight,Rajkiandris, RayChang, Rebecca, Recognizance, Recon Unit, Redshoe2, Reedy, Regibox, Remember, Rettetast, RexNL, Riana, Rich Farmbrough, Rifleman 82, Riverwire, Rjwilmsi, Roadrunner,Robert Foley, Rock2e, Roleplayer, Roni2204, Rosiestep, Royboycrashfan, Rrburke, Rror, Rufus Turner, Rursus, SEWilco, Sammetsfan, Samtheboy, Say2anniyan, Scarian, SchfiftyThree,Schmloof, Scientizzle, Scjessey, Seamarine, Searchme, Selket, Serendipodous, Serveux, Shalom Yechiel, Shanes, Shell Kinney, ShexRox, Shizhao, Sionus, Sketchmoose, Skogen11341, SkyAttacker, Slakr, Sleeping123, Smack, Smalljim, Smeira, Smurfy, SoWhy, SpaceFlight89, Spellmaster, Spencer, SpookyMulder, Squiddy, Stained Illusion, Starfawcks, Stelio, StephenBuxton,Stephenb, Steven Zhang, Stone, Stwalkerster, Supahfreekeh, Superbeecat, Supermake, Sweet xx, Sweetnshort, Symane, TERANADON, TUF-KAT, Taemyr, Talinus, Tangotango, Tantalate,Tc191, Techman224, TehTomeh, The Enslaver, The Flying Spaghetti Monster, The Incredible Editor, The Random Editor, The Thing That Should Not Be, TheCatalyst31,TheGreatAwesomeness, TheHurtProcces, ThePillock, Thenickdude, Theresa knott, Thesexualityofbereavement, Thingg, Tiddly Tom, Tide rolls, Tiptoety, Tommyknee, Triona, Trovatore,Tslocum, TutterMouse, Twas Now, Twp, Tycho, Ulric1313, Una Smith, User27091, Utcursch, Versus22, Voltron, Vsmith, Vuo, W4410ck, WLior, Walkerma, Wavelength, Werdan7, Wesley,White Cat, WikHead, Wikieditor06, Wikilackey, Wikipe-tan, Wikiscient, William Avery, Willtron, Wilson44691, Wimt, Wizard191, Wj32, Wolfrock, Xanthine, Xenon54, Xiru, Yerpo,Yidisheryid, Yintan, Yobmod, Yran01, Z897623, Zaz3494, Zeo197, Ziggy Sawdust, Ziyaad97, Zoicon5, Zzuuzz, Јованвб, Александър, 1458 ,ملاع بوبحم anonymous edits

Metalloid  Source: http://en.wikipedia.org/w/index.php?oldid=380764803  Contributors: Achim1999, Ahoerstemeier, Alansohn, Andre Engels, Army1987, Attilios, Ayrton Prost, Benbest, Binks, Brianski, C1k3, CWii, Calvin 1998, Capricorn42, CaptainVindaloo, Chinagirl5566, Churchilljrhigh, Clanton2, Cobblet, Ctdunstan, DMacks, DR04, Darklilac, Db099221, Deskana, Deutsch Fetisch, Dillard421, Dirgela, DivineAlpha, Dlohcierekim, Dureo, Dylant07, Eaolson, Eeekster, El C, Epbr123, Eru Ilúvatar, FF2010, Feline1, Feministo, FrozenPencil, GPHemsley, Gentgeen, Giftlite, Gilgamesh he, Gilliam, Gscshoyru, Heron, Hippietrail, Hugo-cs, Icairns, Ioeth, Ishiho555, J.delanoy, J4V4, Jaraalbe, Jayron32, JoanneB, Joelster, John254, Keenan Pepper, Keitei, Kimiko, Kjkolb, KlaudiuMihaila, Lahiru k, Laurinavicius, Law, Lethaniol, MER-C, Martin451, Materialscientist, Mav, MaximumPC, Mikemoral, Mild Bill Hiccup, Mirroredlens, Moletrouser, Mr.Z-man, Munita Prasad, Mwtoews, N Shar, Natalefarrell, Neonumbers, Nergaal, Neutrality, NotAnonymous0, On the other side, Pasketti, Philip Trueman, Plankton 22, Polly, Poonu, Pumapo,

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Article Sources and Contributors 158

Quarty, R0pe-196, Radagast, Redchasteen, Remember, Reuben, Rfc1394, Rkuchta, Roentgenium111, Romanm, Rror, SDC, Sampi, Scarian, Sixxgun11, Smack, Squids and Chips, Srnec,Suicidalhamster, Tarquin, Techman224, TimSE, Timwi, Tommy2010, UnfriendlyFire, VI, Voyagerfan5761, Waggers, Wikimac007, Wknight94, WojPob, Xx8zaxo8xx, Yamamoto Ichiro,Yekrats, Yromemtnatsisrep, Zoicon5, 262 anonymous edits

Noble gas  Source: http://en.wikipedia.org/w/index.php?oldid=382361807  Contributors: 1297, 24.253.156.xxx, A Softer Answer, Acey365, Adamn, Adashiel, Adilch, AdultSwim, Agesworth,Ahoerstemeier, Aitias, Aksi great, Alansohn, Alchemist-hp, Aldaron, AlexiusHoratius, Andme2, Andraaide, Andre Engels, Andrewlp1991, Andycjp, Angrysockhop, Animaly2k2, AnnaFrance,Anoop.m, Antandrus, Anthony Duff, Antonjad, Arimareiji, Art LaPella, Artichoker, AxelBoldt, Bachrach44, Bduke, Beetstra, Bellax22, Belovedfreak, Bentleymrk, Betterworld, Blanchardb,Bloody Mary (folklore), Boatcolour, Bombhead, Bongwarrior, Boothy443, Breno, CSWarren, Calliopejen1, Calmer Waters, CalumH93, CanadianLinuxUser, Canderson7, Capricorn42,Cenarium, Chaser, Chaser (away), Chris Dybala, Christian List, Cimex, Cinnamon42, Cjthellama, CommonsDelinker, Conversion script, Coppertwig, DMacks, DVD R W, DanielCD, Dank,Dantheman531, Darth Panda, David Levy, Davidmwhite, Deagle AP, Deglr6328, DerHexer, Derek Ross, DevastatorIIC, Dhruv17singhal, Dina, Discospinster, Dnwq, Donarreiskoffer,Dorothybaez, DrBob, Durova, Eakka, EamonnPKeane, Eddideigel, Edgar181, Eganev, El C, Enigmaman, Enok Walker, Epbr123, Eric Olson, Excirial, Extransit, Feinoha, Feline1, Femto,Finch-HIMself, Fingerginger1, Flauto Dolce, FocalPoint, Fonzy, Franamax, Freestyle-69, Fvw, GCarty, Gaff, Gary King, Gene Nygaard, Gentgeen, Geoking66, Giftlite, GngstrMNKY, GogoDodo, Goudzovski, GrahamColm, Gscshoyru, Gökhan, Hadal, Haham hanuka, HappyCamper, Hasek is the best, Hdt83, Hephaestos, Herbee, HereToHelp, Hibou8, I own in the bed, IRP,IanOsgood, Icairns, InShaneee, Iridescent, IsFari, Isaac Dupree, Itub, J.delanoy, JForget, JGHowes, JHunterJ, JaGa, JackofOz, Jaganath, JaimeAnnaMoore, Jake Nelson, Jakohn, Jaksmata,Japheth the Warlock, Jared81, Jauerback, Jaxl, Jcsdude, Jeff G., Jeri Aulurtve, Jimfbleak, John, Jordan776, Jusdafax, KChiu7, Kablammo, Kandar, Karn, Kay Dekker, Keenan Pepper, Keepiru,Keilana, Kilo-Lima, King of Hearts, KnowledgeOfSelf, LC, LOL, Latka, Law, Lenaic, Leptictidium, LibLord, Lightmouse, Ling.Nut, Little Mountain 5, Lolcopter666, Lop242438, LorenzoB,Luna Santin, Lupo, MJCdetroit, Manbearpig4, Marco Polo, Marine79, Materialscientist, Matjlav, Matthardingu, Mattinbgn, Mattisse, Mav, Maxis ftw, Mentifisto, Merovingian, Mervyn, MikeRosoft, Mjp797, Monedula, Moshe Constantine Hassan Al-Silverburg, Mpatel, Mr0t1633, Muro de Aguas, Najlepszy, Nakon, Nathan, Navneethmohan, NawlinWiki, NeilN, NeilTarrant, Nergaal,NewEnglandYankee, Nicholas Tan, Nielg, Nihiltres, Nikai, Nimbusania, Noah Salzman, Nousernamesleft, Nsaa, Numerjeden, Obradovic Goran, Olivier, Ollie holton, Optimale, Orangemarlin,Owainbut, Paul August, Paul-L, Paxsimius, PerpetualSX, Pharaoh of the Wizards, Phgao, Philip Trueman, Phillip.northfield, Photonikonman, Piledhigheranddeeper, Pinethicket, Plasticup,Plumbago, Poigol5043, Pol098, Polartsang, Ponder, Popopee, Possum, Quackor, RJHall, Ranveig, Reach Out to the Truth, Remember, RexNL, RexxS, Rfc1394, Rich Farmbrough, Rjwilmsi,Rlandmann, RobertG, Robinh, Robth, Roentgenium111, Romanm, Ronhjones, Rrburke, Runtishpaladin, Ruslik0, Salsa Shark, Salvio giuliano, Sam Hocevar, Sander123, SandyGeorgia, Scepia,Scerri, Scorpion451, Scoutersig, SeanFarris, Semperf, Seresin.public, Severious, Shanedidona, Shanes, Shantavira, Shay Guy, Shellreef, Shenme, Sidias300, Sietse Snel, Slakr, Slyguy, Slysplace,Smack, Smokefoot, Smot94, Sohelpme, SpeedyGonsales, Squids and Chips, StephenBuxton, Stevey7788, Stone, Strangnet, Straussian, Surfrat60793, Suruena, Swampgas, Sylent, Synchronism,T-rex, Taoster, TarmoK, Tarquin, Tarret, Tero, Tetracube, That Guy, From That Show!, The Evil Spartan, The Thing That Should Not Be, The undertow, Theleftorium, Themaxviwe,Thetoaster3, Thibbs, Thingg, Tide rolls, TinribsAndy, Titus III, Triwbe, Turk oğlan, UKe-CH, Uncle Dick, Vary, Versus22, Viriditas, Vsmith, Vssun, Vuo, Vuong Ngan Ha, WadeSimMiser,Wandering Ghost, Wayward, Werdnanoslen, Werson, Widey, Wikieditor06, WinterSpw, Wizardman, Woohookitty, Xnuiem, Yopure, Yyy, Zaphraud, Zirland, Zzuuzz, 650 anonymous edits

Noble metal  Source: http://en.wikipedia.org/w/index.php?oldid=381749957  Contributors: Abdull, Achim1999, Amberroom, Art LaPella, Asfarer, Benbest, Bgpaulus, Bluemoose, Borgx,Chem-awb, Chemicalinterest, Christophenstein, Cmjayakumar, Common Man, Donfbreed, DopefishJustin, EgraS, Enochlau, Enz, Everyking, Fangjian, Gioto, Hede2000, Icairns, Ike9898, Itub,Knuckles, Kpjas, Magog the Ogre 2, Mandarax, Materialscientist, McDoobAU93, Mccready, Michał Sobkowski, Mtz1010, N2e, PhilKnight, Physchim62, Polyparadigm, RandomP, Rayc,Rifleman 82, Rune.welsh, Rursus, Scientific29, Scyldscefing, Seth Nimbosa, Skittle, Sligocki, Smackeldorf, Tablemajorrt5, The Anome, UnitedStatesian, Viriditas, Voyevoda, Wayiran,Whosyourjudas, Wizard191, 44 anonymous edits

Nonmetal  Source: http://en.wikipedia.org/w/index.php?oldid=379530796  Contributors: 14albeev, 56, Acather96, Ahoerstemeier, Aleenf1, Andre Engels, Anoop.m, Barticus88, Benjah-bmm27,Bobo192, Bomac, Branddobbe, CardinalDan, Carnildo, Cosmium, Courcelles, D6, DMacks, Dungodung, Eb.eric, Edgar181, Element16, Epbr123, Eric119, Eru Ilúvatar, Feline1, Flewis,Fluffybun, Funnyfarmofdoom, Gallador, Gene Nygaard, Genius695, Gentgeen, Geraki, Gilliam, GregorB, HappyCamper, Heron, How to save a life, Hugo-cs, Icairns, Immunize, IndianChronicles, Jcw69, Jusjih, Kateshortforbob, Kayau, Keenan Pepper, Kim Bruning, KlaudiuMihaila, KnowledgeOfSelf, Kostaki mou, Kw0, LeaveSleaves, Leszek Jańczuk, Leujohn, Liamgales,Life of Riley, Looxix, Lova Falk, Mendaliv, Mentifisto, Michael Devore, Monkeysack420, Mr.Z-man, Munita Prasad, Nappymonster, Nebular110, Nergaal, Nivix, Nuggetboy, Orbst, P Carn,Paul Foxworthy, Paul-L, Piano non troppo, Pinethicket, Possum, RJaguar3, Remember, Rfc1394, Roentgenium111, Romanm, Ronhjones, Saperaud, Semprini, SethBoldt, Shellreef, Smack,Smihael, Squids and Chips, Sunny910910, TheOner, Thewonderidiot, Trusilver, Vsmith, Wimt, 178 anonymous edits

Platinum group  Source: http://en.wikipedia.org/w/index.php?oldid=373355559  Contributors: 7d5a3220, Afisch80, Ariedartin, Barticus88, Bearcat, Bobo192, Brockert, CERminator, Causa sui,Charles Gaudette, Cmjayakumar, Colbuckshot, Crust, Cryptic C62, Darklilac, David Richtman, DerHexer, DimaY2K, DocWatson42, Ezra Wax, FastLizard4, Feline1, Feťour, Gadfium, Garwod,Gioto, IRP, Iridescent, IronyWrit, Jasev01, Karl-Henner, KnightRider, Krassotkin, Kurykh, Larry Grossman, Materialscientist, McTrixie, Mentifisto, Mikespedia, N2e, Nergaal, Nnh, Paul D.Anderson, Paul venter, PaulHanson, Phantomsteve, Pyrochem, Reality006, RoyBoy, Shaddack, Shanedidona, Skatebiker, Smac2020, Stone, Su-no-G, Tamil.tpt, The Anome, Tide rolls, Vsmith,WpZurp, Yamamoto Ichiro, Zappon, Zero over zero, 106 anonymous edits

Post-transition metal  Source: http://en.wikipedia.org/w/index.php?oldid=381464583  Contributors: Brane.Blokar, Cybercobra, DocWatson42, Filmore123, Flyguy649, Flying Jazz, Fritzpoll,Hellbus, Icairns, Isla Nublar, John, JustObserver, N2e, Nergaal, Onevalefan, Prodego, Skizzik, SquareOuroboros, Syp, Thumperward, Vsmith, Wizard191, 百家姓之四, 8 anonymous edits

Transactinide element  Source: http://en.wikipedia.org/w/index.php?oldid=381999427  Contributors: Bob Saint Clar, DMacks, Eddideigel, Flying Jazz, FourteenDays, Gene Nygaard, Ghjthgh,Glenn4pr, Icairns, Joelholdsworth, John, Kurykh, MagnaGraecia, Mpatel, Nergaal, Rursus, Russoc4, Warut, 14 anonymous edits

Transuranium element  Source: http://en.wikipedia.org/w/index.php?oldid=376129299  Contributors: -- April, 64.26.98.xxx, Abcdefgy2, Acer, AgnosticPreachersKid, Alex43223, AndreEngels, Antandrus, Arichnad, Beardo, Benbest, Bk0, Bootstoots, Borgx, Brian0918, Bryan Derksen, CP\M, Cadmium, CanisRufus, Cfsgfds, Chaityacshah, Chaojoker, Chris 73, Conversionscript, Corti, DMacks, Dilbert3, Dirkbb, Dor Cohen, DrTorstenHenning, Dreish, Efficiency1101e, El C, Eric119, Eweisser, Eyu100, Fibonacci, Finlay McWalter, Fiveless, Flywhc, Fonzy, GSRoP, GeeJo, Gene Nygaard, Glenn L, Gorank4, Gritchka, Hairy Dude, Headbomb, IW.HG, Icairns, Improv, Itinerant1, JeLuF, Jeepday, Jeff G., Jnestorius, John, Julesd, Karl Dickman, Kelovy,Kiyura, Kurykh, Kzollman, Leaflet, Lysdexia, MPF, Mashford, Materialscientist, Meno25, Mentifisto, MichaelVernonDavis, Mjpotter, Nergaal, Nibuod, Nightstallion, Noctibus, Novangelis,Okedem, Oleg Alexandrov, Patrick, Paul Drye, Pauli133, Physchim62, Piotrus, Qutezuce, RG2, RUL3R, Reyk, Rlaager, Rmhermen, Roo72, Rursus, Ryoung122, Shanes, Skunkboy74,Snailwalker, Stepheng3, Stirling Newberry, Stone, Stratocracy, Surv1v4l1st, Svgalbertian, Synchronism, TakuyaMurata, Taraborn, The Anome, Tim Starling, Trewal, Trumpet marietta 45750,TwoOneTwo, Van helsing, Vsmith, Warut, Whiner01, Xavexgoem, Ytrepus, Zarboki, Zundark, 142 anonymous edits

Transition metal  Source: http://en.wikipedia.org/w/index.php?oldid=380998386  Contributors: ABF, Ahoerstemeier, Ahruman, Aksi great, Alansohn, Andonic, Andrewa, Arkuat,Atraxendeluge, Axl, Ayudante, Bandn, Benbest, Benjah-bmm27, BlueDevil, Bogey97, Bryan Derksen, Capricorn42, Centrx, CharlotteWebb, Chris 73, Christopher Parham, Chrumps, ChuunenBaka, Cmdrjameson, Coldphoenix182, Cometstyles, Commander, Conversion script, Courcelles, Cremepuff222, DMacks, Da monster under your bed, Darrien, Dawn Bard, Dax max, Denali134,Derek Ross, Dferg, Dirac66, Dungodung, Echidna, Edgar181, Eivindgh, Elysdir, Epbr123, Epitaf, Erc, Eric-Wester, Eric119, Eru Ilúvatar, Excession, Felix Wan, Femto, Fieldday-sunday, Flewis,Flying Jazz, Fogster, Fphilx, Frehley, Frozenguild, FvdP, Fyyer, Gail, Gentgeen, George The Dragon, Gerweck, Gilliam, Gogo Dodo, Graham87, Gulliveig, Gurkha711, Gwdr500, Gwernol,Haosys, Heart of a Lion, Hetar, Hugo-cs, Hunnjazal, Icairns, ImperatorExercitus, Iolo, Iridescent, J.delanoy, JakeVortex, Jdrewitt, Jeff3000, Josh Parris, Jumping cheese, Jusjih, Kaal, KarenJohnson, Keenan Pepper, Kimiko, King of Hearts, Kingpin4646, Koyaanis Qatsi, Kryan5, Kukini, Kumorifox, Lanky, Latka, Lee Daniel Crocker, Lfh, Looxix, LouisBB, Lysdexia, MER-C,MONGO, Mangwanani, Materialscientist, Mav, Measles92793, Melsaran, Michael Hardy, Micro.pw, Monkeyskate1, Mtodorov 69, Nakon, NellieBly, Nergaal, Newportm, Nippoo, OMCV, Olin,Orcoteuthis, Orienteer05, Pandora Xero, Passw0rd, Patteroast, Petergans, Philip Trueman, Physchim62, Piano non troppo, Pjvpjv, Polyparadigm, Prashanthns, QmunkE, R8R Gtrs,Ravichandar84, Reaverdrop, Reinyday, Remember, Rfc1394, Rjstott, Rjwilmsi, Rkmlai, Rockincon1, Ronline, RoyBoy, Runnerboy4444, Sam Korn, Scarian, ScatheMote100, Schmloof,Sharabura, Shootbamboo, Sintau.tayua, Smalljim, Smokefoot, Sodium, Squids and Chips, StonedChipmunk, Sushi, THEN WHO WAS PHONE?, Tarif Ezaz, Tetracube, Thingg, Tijuana Brass,Timemutt, Titus III, Tohd8BohaithuGh1, Tone, Trampled, Treisijs, Tressor, Twas Now, Uncle Dick, Vsmith, Waggers, Wambo, Wapcaplet, WereSpielChequers, William Avery, Willking1979,Wknight94, WmRowan, Woppit, Xiahou, Xoder, Yakiea, Yamamoto Ichiro, Yath, Zfr, Ziggy Sawdust, Zubyrhassan1, 에멜무지로, 483 anonymous edits

Table of nuclides  Source: http://en.wikipedia.org/w/index.php?oldid=382135078  Contributors: Abc518, Achim1999, Alansohn, Bob Bryan, Cflm001, Colinsweet, D-rew, David spector,DenverRedhead, Donko XI, Efficiency1101e, Ewen, Giftlite, Greg L, Heron, Itub, JWB, Jmocenigo, KaiMartin, Kristhof, Kwamikagami, LastRanger, Mikhajist, Minivip, Mnmngb, My Flatley,Ntouran, NukeMan, Quilbert, Rich Farmbrough, Rod57, Rorro, Sbharris, Shinkolobwe, Timwi, Tjlafave, TraceyR, UpstateNYer, User A1, WFPM, ZooFari, 26 anonymous edits

Island of stability  Source: http://en.wikipedia.org/w/index.php?oldid=381527892  Contributors: Alexwcovington, AxelBoldt, Bearian, Benbest, Bender235, Bhangranuch, Biblbroks, Buster79,Cdrk, ChaosR, Chmod007, Chrumps, Coemgenus, Control.valve, Dale101usa, Deewiant, Dude1818, Długosz, Ed Cormany, Edgar181, Eequor, Efficiency1101e, Einstein dark energys, EmptyBuffer, Emurphy42, Eric119, Eyu100, FrankH, Furrykef, Giftlite, Glenn L, GregorB, Hateless, Icairns, Inverse Tiger, JDspeeder1, JLM, JMTCP, JWB, Jaganath, Jayapura, John, Jpatokal,Keenan Pepper, Kevin Baas, Kieff, Kurykh, Kwamikagami, Lamro, Lexicon, Limulus, LorenzoB, MarSch, Maralia, Mets501, Michael Snow, Miss Madeline, Morgoroth4, Mr. Billion,Musiqueue, N. Harmonik, Nergaal, Netdragon, Niczar, Northfox, Nwbeeson, Olin, OttoMäkelä, Pauli133, Paulomatsui, Piperh, Planet-man828, Polonium, Pwjb, Quilbert,RODERICKMOLASAR, Remember, Reyk, Rich Farmbrough, Rifleman 82, Rjwilmsi, Roadrunner, Rod57, Roentgenium111, Rursus, ST47, Seattle Skier, Shirifan, Shogunzhu, SimonP, Sirdigby 121, Slawojarek, Smack, Smithbrenon, Stirling Newberry, Stone, Superheavy120, Svgalbertian, TerraFrost, Tetracube, The way, the truth, and the light, Thue, Tillman, Timwi,Vanderdecken, Vicki Rosenzweig, Warut, Whitepaw, Who, Writtenright, Wtaa, Wwoods, Xanthine, Xezbeth, Yosha, Ytrottier, ~K, 99 anonymous edits

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Image Sources, Licenses and ContributorsFile:PTable structure.png  Source: http://en.wikipedia.org/w/index.php?title=File:PTable_structure.png  License: GNU Free Documentation License  Contributors: Sch0013rImage:Ionization energies.png  Source: http://en.wikipedia.org/w/index.php?title=File:Ionization_energies.png  License: Public Domain  Contributors: User:RJHallFile:Medeleeff by repin.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Medeleeff_by_repin.jpg  License: unknown  Contributors: Hailey C. Shannon, J.M.Domingo, Kevyn,Kneiphof, Maximaximax, OldakQuill, Ragesoss, Shakko, Solon, XJamRastafire, 竹麦魚(Searobin), 2 anonymous editsFile:The Periodic Table.PNG  Source: http://en.wikipedia.org/w/index.php?title=File:The_Periodic_Table.PNG  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:Arman CagleImage:Periodic table discovery periods.png  Source: http://en.wikipedia.org/w/index.php?title=File:Periodic_table_discovery_periods.png  License: Attribution  Contributors: IUPACImage:Lavoisier.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Lavoisier.jpg  License: Public Domain  Contributors: DavidFile:PTE-Law of Octaves.svg  Source: http://en.wikipedia.org/w/index.php?title=File:PTE-Law_of_Octaves.svg  License: Creative Commons Attribution-Sharealike 2.0  Contributors:User:SponkImage:Mendelejevs periodiska system 1871.png  Source: http://en.wikipedia.org/w/index.php?title=File:Mendelejevs_periodiska_system_1871.png  License: Public Domain  Contributors:Original uploader was Den fjättrade ankan at sv.wikipediaImage:Дмитрий Иванович Менделеев 4.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Дмитрий_Иванович_Менделеев_4.gif  License: Public Domain  Contributors: Anrie,Materialscientist, Mav, Maximaximax, OldakQuillImage:Mendeleev Table 5th II.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Mendeleev_Table_5th_II.jpg  License: Public Domain  Contributors: Ragesoss, 3 anonymous editsFile:Periodic table discovery periods.png  Source: http://en.wikipedia.org/w/index.php?title=File:Periodic_table_discovery_periods.png  License: Attribution  Contributors: IUPACImage:Elementspiral.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Elementspiral.svg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: DZadventiste,Edgar181, Latenightwithjimmyfallon, Matthias M.Image:Periodic table.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Periodic_table.svg  License: Public Domain 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User:DhatfieldImage:P5M-1.png  Source: http://en.wikipedia.org/w/index.php?title=File:P5M-1.png  License: Public Domain  Contributors: User:DhatfieldImage:D5M0.png  Source: http://en.wikipedia.org/w/index.php?title=File:D5M0.png  License: Public Domain  Contributors: User:DhatfieldImage:D5M1.png  Source: http://en.wikipedia.org/w/index.php?title=File:D5M1.png  License: Public Domain  Contributors: User:DhatfieldImage:D5M-1.png  Source: http://en.wikipedia.org/w/index.php?title=File:D5M-1.png  License: Public Domain  Contributors: User:DhatfieldImage:D5M2.png  Source: http://en.wikipedia.org/w/index.php?title=File:D5M2.png  License: Public Domain  Contributors: User:DhatfieldImage:D5M-2.png  Source: http://en.wikipedia.org/w/index.php?title=File:D5M-2.png  License: Public Domain  Contributors: User:DhatfieldImage:S6M0.png  Source: http://en.wikipedia.org/w/index.php?title=File:S6M0.png  License: Public Domain  Contributors: User:Dhatfield

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Image:P6M0.png  Source: http://en.wikipedia.org/w/index.php?title=File:P6M0.png  License: Public Domain  Contributors: User:DhatfieldImage:P6M1.png  Source: http://en.wikipedia.org/w/index.php?title=File:P6M1.png  License: Public Domain  Contributors: User:DhatfieldImage:P6M-1.png  Source: http://en.wikipedia.org/w/index.php?title=File:P6M-1.png  License: Public Domain  Contributors: User:DhatfieldImage:S7M0.png  Source: http://en.wikipedia.org/w/index.php?title=File:S7M0.png  License: Public Domain  Contributors: User:DhatfieldImage:Alkalimetalle.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Alkalimetalle.jpg  License: GNU Free Documentation License  Contributors: Benutzer:TomihahndorfImage:Erdalkali.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Erdalkali.jpg  License: GNU Free Documentation License  Contributors: User Tomihahndorf on de.wikipediaFile:Scandium_sublimed_dendritic_and_1cm3_cube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Scandium_sublimed_dendritic_and_1cm3_cube.jpg  License: Attribution Contributors: User:Alchemist-hpFile:Yttrium_sublimed_dendritic_and_1cm3_cube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Yttrium_sublimed_dendritic_and_1cm3_cube.jpg  License: Attribution Contributors: User:Alchemist-hpFile:Titan-crystal bar.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Titan-crystal_bar.JPG  License: GNU Free Documentation License  Contributors: Alchemist-hp (pse-mendelejew.de)File:Zr-crystal-bar.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Zr-crystal-bar.jpg  License: Free Art License  Contributors: User:Alchemist-hpFile:Hf-crystal bar.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Hf-crystal_bar.jpg  License: Attribution  Contributors: User:Alchemist-hpFile:Ilmenit - Miask, Ural.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ilmenit_-_Miask,_Ural.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:Ra'ikeImage:HeavyMineralsBeachSand.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:HeavyMineralsBeachSand.jpg  License: Public Domain  Contributors: Photograph taken by MarkA. Wilson (Department of Geology, The College of Wooster).File:Vanadium_etched.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Vanadium_etched.jpg  License: Attribution  Contributors: User:Alchemist-hpFile:Niobium_crystals_and_1cm3_cube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Niobium_crystals_and_1cm3_cube.jpg  License: GNU Free Documentation License Contributors: User:Alchemist-hpFile:Tantalum_single_crystal_and_1cm3_cube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tantalum_single_crystal_and_1cm3_cube.jpg  License: GNU Free DocumentationLicense  Contributors: User:Alchemist-hpFile:Chromium_crystals_and_1cm3_cube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Chromium_crystals_and_1cm3_cube.jpg  License: GNU Free Documentation License Contributors: User:Alchemist-hpFile:Molybdenum_crystaline_fragment_and_1cm3_cube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Molybdenum_crystaline_fragment_and_1cm3_cube.jpg 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Benjah-bmm27Image:Coloured-transition-metal-solutions.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Coloured-transition-metal-solutions.jpg  License: Public Domain  Contributors:Benjah-bmm27, Jafeluv, Pieter Kuiper, WikipediaMaster, 3 anonymous editsfile:Actinides radii.png  Source: http://en.wikipedia.org/w/index.php?title=File:Actinides_radii.png  License: Public Domain  Contributors: User:PetergansFile:HoOxideSolution.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:HoOxideSolution.jpg  License: Public Domain  Contributors: NISTFile:Elemental abundances.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Elemental_abundances.svg  License: Public Domain  Contributors: User:michbichImage:Gallium1 640x480.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gallium1_640x480.jpg  License: unknown  Contributors: -Image:Hot metalwork.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Hot_metalwork.jpg  License: unknown  Contributors: 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File:Xenon discharge tube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Xenon_discharge_tube.jpg  License: unknown  Contributors: User:Alchemist-hpFile:HeTube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:HeTube.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:PslawinskiFile:NeTube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:NeTube.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:PslawinskiFile:ArTube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:ArTube.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:PslawinskiFile:KrTube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:KrTube.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:PslawinskiFile:XeTube.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:XeTube.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:PslawinskiFile:Helium_spectra.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Helium_spectra.jpg  License: Public Domain  Contributors: User:MrgoogfanFile:Neon.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Neon.jpg  License: Public Domain  Contributors: User:MrgoogfanFile:Argon_Spectrum.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argon_Spectrum.jpg  License: Public Domain  Contributors: User:MrgoogfanFile:Krypton_Spectrum.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Krypton_Spectrum.jpg  License: Public Domain  Contributors: User:MrgoogfanFile:Xenon_Spectrum.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Xenon_Spectrum.jpg  License: Public Domain  Contributors: User:MrgoogfanImage:Edelmetalle.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Edelmetalle.jpg  License: GNU Free Documentation License  Contributors: .Image:Super heavy elements.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Super_heavy_elements.svg  License: Public Domain  Contributors: ArichnadImage:Periodic Table Radioactivity.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Periodic_Table_Radioactivity.svg  License: GNU Free Documentation License  Contributors:User:Alessio Rolleri, User:Armtuk, User:GringerImage:NuclideMap small preview.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:NuclideMap_small_preview.jpg  License: Public Domain  Contributors: The viewerImage:Compact Isotope Table, Right Lobe.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Compact_Isotope_Table,_Right_Lobe.jpg  License: Creative CommonsAttribution-Sharealike 3.0  Contributors: User:DenverRedheadImage:Island-of-Stability.png  Source: http://en.wikipedia.org/w/index.php?title=File:Island-of-Stability.png  License: GNU Free Documentation License  Contributors: Original uploader wasXanthine at en.wikipedia Later version(s) were uploaded by McLoaf at en.wikipedia.

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License 162

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