Periodic Table

Mendeleyev, Dmitry (Discover of Periodic Table)

Mendeleyev also spelled Mendeleev Born : Feb. 8, 1834, Tobolsk, Siberia, Russia Died : Feb. 2, 1907, St. Petersburg

He was a professor of chemistry at the University of St. Petersburg (1867–90) and later served as director of Russia's bureau of weights and measures. He made a fundamental contribution to chemistry by announcing in 1869 the principle of periodicity of properties in the chemical elements. His periodic table was based on this principle, arranging the elements in ascending order of atomic weight and grouping them by similarity of properties. Mendeleyev's theory allowed him to predict the existence and atomic weights of several elements not discovered until years later.

Periodic tableOrganized array of all the chemical elements in approximately

increasing order of their atomic weight.The elements show a periodic recurrence of certain properties, first

discovered in 1869 by Dmitry I. Mendeleyev. Those in the same column (group) of the table as usually arranged have similar properties. In the 20th century, when the structure of atoms was understood, the table was seen to precisely reflect increasing order of atomic number. Members of the same group in the table have the same number of electrons in the outermost shells of their atoms and form bonds of the same type, usually with the same valence; the noble gases, with full outer shells, generally do not form bonds. The periodic table has thus greatly deepened understanding of bonding and chemical behaviour. It also allowed the prediction of new elements, many of which were later discovered or synthesized

What is atomic Weight ?Ratio of the average mass of a chemical element's atoms

to 1/12 the mass of an atom of the carbon-12 isotope.The original standard of atomic weight, established in the

19th century, was hydrogen, with a value of 1. From c. 1900 until 1961, the reference standard was oxygen, with a value of 16, and the unit of atomic mass was defined as 1/16 the mass of an oxygen atom. Oxygen, however, contains small amounts of two isotopes that are heavier than the most abundant one, and 16 is actually a weighted average of the masses of the three isotopes of oxygen. Therefore, the standard was changed to one based on carbon-12. The new scale required only minimal changes to the values that had been used for chemical atomic weights.

What is Electron ?Lightest electrically charged subatomic particle known.It carries a negative charge (see electric charge), the basic

charge of electricity. An electron has a small mass, less than 0.1% the mass of an atom. Under normal circumstances, electrons move about the nucleus of an atom in orbitals that form an electron cloud bound in varying strengths to the positively charged nucleus. Electrons closer to the nucleus are held more tightly. The first subatomic particle discovered, the electron was identified in 1897 by J. J. Thomson.

What is Valence ?Number of bonds (see bonding) an atom can form.Hydrogen (H) always has valence 1, so other elements'

valences equal the number of hydrogen atoms they combine with. Thus, oxygen (O) has valence 2, as in water (H2O); nitrogen (N) has valence 3, as in ammonia (NH3); and chlorine (Cl) has valence 1, as in hydrochloric acid (HCl). The valence depends on the number of unpaired electrons in the outermost (and, in transition elements, the next) shell of the atom's structure. The sharing of the unpaired (valence) electrons in a bond mimics the stable configuration of the noble gases, whose outer shells are full. Elements that can achieve stable configurations by various combinations have more than one valence.

What is bonding ?Any of the interactions that account for the association of atoms into molecules,

ions, crystals, metals, and other stable species.When atoms' nuclei and electrons interact, they tend to distribute themselves

so that the total energy is lowest; if the energy of a group arrangement is lower than the sum of the components' energies, they bond. The physics and mathematics of bonding were developed as part of quantum mechanics. The number of bonds an atom can form—its valence—equals the number of electrons it contributes or receives. Covalent bonds form molecules; atoms bond to specific other atoms by sharing an electron pair between them. If the sharing is even, the molecule is not polar; if it is uneven, the molecule is an electric dipole. Ionic bonds are the extreme of uneven sharing; certain atoms give up electrons, becoming cations. Other atoms take up the electrons and become anions. All the ions are held together in a crystal by electrostatic forces. In crystalline metals, a diffuse electron sharing bonds the atoms (metallic bonding). Other types include hydrogen bonding; bonds in aromatic compounds; coordinate covalent bonds; multicentre bonds, exemplified by boranes (boron hydrides), in which more than two atoms share electron pairs; and the bonds in coordination complexes (see transition element), still poorly understood

The Long Form of Periodic Table

Element of First Period

The first period corresponding to n = 1 is unique because it contains only two element. There can accommodate only two electron in which one & two electron are present in the first energy level. The first Period contain hydrogen (1s) and helium (1s).

Element of Second Period

The second period contain 8 element because for n = 2, there are four orbitals I second energy shell (L). In all, these four orbital have a capacity of eight electron and therefore, second period has eight element in it.

It Start with Lithium (Z = 3) and with Neon(Z = 10) in which the second shell is

completed.

Element of Third Period

In Third group Corresponding to n = 3, there are nine orbital : one 3s, three 3p and five 3d. This period involves the filling of only four orbitals (3s and 3p) and contains eight element from sodium (Z = 11) to argon (Z = 18).

Element of Fourth Period

In Third group Corresponding to n = 4 involves the filling of one 4s-and three 4p-orbitals. There are 18 element from potassium (Z = 19) to Krypton (Z = 36).

Element of Fifth Period

The Fifth period, like the fourth period also consist of 18 element. It begins with rubidium (Z = 37) with filling 5p-orbitals and ends at xenon (Z = 54). This period also contain ten element of 4d Transition series starting at yttrium (Z = 39)

Element of Sixth PeriodA period 6 element is one of the chemical elements in the sixth row (or

period) of the periodic table of the elements, including the lanthanides. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases: a new row is begun when chemical behavior begins to repeat, meaning that elements with similar behavior fall into the same vertical columns. The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon. Lead is currently the last stable element; all subsequent elements are radioactive, however bismuth has a half-life of more than 1019 years, more than 1,000 times longer than the current age of the universe. As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order, however there are exceptions, such as cerium.

Element of Seven PeriodThe halogens are located in Group VIIA of the periodic table, and are a

particular class of nonmetals. The halogen elements are fluorine, chlorine, bromine, iodine.

These reactive nonmetals have seven valence electrons. As a group, halogens exhibit highly variable physical properties. Halogens range from solid (I2) to liquid (Br2) to gaseous (F2 and Cl2) at room temperature. The chemical properties are more uniform. The halogens have very high electro negativities. Fluorine has the highest electro negativity of all elements. The halogens are particularly reactive with the alkali metals and alkaline earths, forming stable ionic crystals. tine, and ununseptium.

Division of Element Into s, p,

d and f Blocks

S-Block ElementThe element in which the last electron the s-orbital of

their outermost energy level are called s-block element.

It consist of element of group 1 & 2.The group 1 element are called Alkali Metals.The group 2 element are called Alkaline Earth

Metals.

np1-2

Characteristics of s-block element

i. They are soft metals having low melting and boiling point.

ii. They have low ionisation enthalpies.iii. They are very reactive.iv. They mostly form ionic compound except

lithium and beryllium.

p-Block ElementThe element in which the last electron the p-orbital

of their outermost energy level are called s-block element.

It consist of element of group 13 & 18.General electric configuratuon of p block element

are :

ns2 np1-6

p-Block Element

d-Block ElementThe element in which the last electron the p-orbital

of their last but one (called penultimate) energy level are called s-block element.

This block consist of the element lying between s and p blocks. It consist of element of group 3 & 12.

General electric configuration of p block element are :

(n-1)d1-10 ns1 or 2

d-Block Element

Characteristics of d-block element

i. They are metal having high melting and boiling point.

ii. Most of them form coloured compound.iii. They have good tendency to form

complex compounds.iv. Their conpounds are generally

paramagnetic.

f-Block ElementThe element in which the last electron the f-

orbital of their atom are called s-block element.

In hese element , the last electron is added to the third to the outermost (called antipenultimate) energy level; (n-2)f.

These consist of two series of element placed at te bottom of the Periodic Table

A. The first series follows lanthanum,LA (Z = 57) and the element present in this series {CE (58) – LU(71) }

B. The second series follows actinium,AC (Z = 89) and the element present in this series {TH(90) – LR(103) }.

General electric configuration of p block element are :

(n-2)f1-14 (n-1)d0-2 ns2

f-Block Element

Characteristics of f-block element

i. They are heavy metalsii. They generally have high melting and

boiling point. iii. They exhibit variable oxidation states.iv. They form coloured compounds.v. They have tendency to form Complex

compounds.

Classification of elements in General Types

1. Noble GasesAny of the seven chemical elements that make up the rightmost group

of the periodic table as usually arranged : helium, neon, argon, krypton, xenon, radon, and element 118.

All are colorless, odorless, and nonflammable and, except for element 118, occur in tiny amounts in the atmosphere (though helium is the most plentiful element in the universe after hydrogen). Their stable electronic configurations, with no unpaired electrons to share, make them extremely unreactive—hence “noble” (i.e., aloof) or inert—though krypton, xenon, and radon, with outer electrons held less firmly, can form compounds (mainly with fluorine). These gases absorb and give off electromagnetic radiation in a much less complex way than other substances, a property exploited in their use in fluorescent lighting devices and discharge lamps. They glow with a characteristic color when confined in a transparent container at low pressure with an electric current passing through it. Their very low boiling and melting points make them useful as refrigerants for low-temperature research

2. Transition elementAny chemical element with valence electrons in two shells instead of only one.This structure gives them their outstanding ability to form ions containing more

than one atom (complex ions, or coordination compounds), with a central atom or ion (often of a transition metal) surrounded by ligands in a regular arrangement. Theories on the bonding in these ions are still being refined. The elements in the periodic table from scandium to copper (atomic numbers 21–29), yttrium to silver (39–47), and lanthanum to gold (57–79, including the lanthanide series) are frequently designated the three main transition series. (Those in the actinide series and beyond, 89–111, also qualify.) All are metals, many of major economic or industrial importance (e.g., iron, gold, nickel, titanium). Most are dense, hard, and brittle, conduct heat and electricity well, have high melting points, and form alloys with each other and other metals. Their electronic structure lets them form compounds at various valences. Many of these compounds are coloured and paramagnetic (see paramagnetism) and (as do the metals themselves) often act as catalysts

THANK YOUName : MUKUL

Class : XI