Periodic Table of Elements Periodic Table of Elements

Periodic TablePeriodic TableIs a tabular arrangement of the

chemical elements organized on the basis of their atomic number, electronic configurations and recurring chemical properties.

Development of the Periodic Table

Johann Wolfgang Dobereiner’s Johann Wolfgang Dobereiner’s Triads (1817)Triads (1817)

He grouped the elements, which exhibit very similar characteristics into triads.

The atomic weight of the second element was found to be the average of the first and third elements.

Atomic weight could be used to determine the position of the elements in the periodic table.

Berzelius (1828)Berzelius (1828)published his table of atomic masses containing 54 elements. Most of his values conform with those in the modern periodic table.

John Newlands (1864)John Newlands (1864) an English chemist, arranged the

elements in an order of increasing atomic mass.

He arranged elements in groups with seven members each similar to the octave of the musical scale.

Referred to as Newlands’ Law of Octaves.

Julius Lothar Meyer (1830-1895)Julius Lothar Meyer (1830-1895)

o He was working on his periodic table consisting of 56 elements.

o He maintained that the properties of the elements were functions of their atomic mass and prepared a graph wherein he plotted the atomic volume of the elements against its atomic mass.

Dmitri MendeleevDmitri MendeleevIn 1869, he created the first accepted In 1869, he created the first accepted

version of the periodic table. version of the periodic table. He arranged the elements in order of He arranged the elements in order of

increasing atomic weight providing increasing atomic weight providing intervals on periods which were not intervals on periods which were not always of the same length.  always of the same length. 

Blank spaces were left open to add Blank spaces were left open to add the new elements he predicted would the new elements he predicted would occur.occur.

The early periodic tables were arranged according to increasing atomic weights and this misplaced several elements, such as Argon, Ar (A= 40)and Potassium, K (A=39), Cobalt, Co (A= 58.9) and Nickel, Ni (A= 58.7), Tellerium, Te (A= 128) and Iodine, I (A=127) in the periodic table.

Henry Moseley (1911)Henry Moseley (1911)He suggested that it was the charge

of the nucleus and not the atomic weight that accounted for the periodic trends in the properties of the elements. Thus, the position of elements in the periodic table is showed by the atomic number.

This concept gave rise to the Modern Periodic Table.

The Modern Periodic LawThe Modern Periodic Law states that there is a periodic states that there is a periodic

repetition of chemical and physical repetition of chemical and physical properties of the elements when properties of the elements when they are arranged in increasing they are arranged in increasing atomic number.atomic number.

Features of the Periodic Features of the Periodic TableTable

The periodic table is divided into horizontal rows called PERIODS or SERIES and the vertical columns are called GROUPS or FAMILIES.

Periods are assigned in Arabic numerals 1 to 7.

Families are assigned in Roman numerals (paired with A or B)

IA to VIIIA and IB to VIIIB

Metals, Non-Metals and Metals, Non-Metals and MetalloidsMetalloids

Elements can be classified as metals, non-metals and metalloids.

Metals are elements that are good conductors of heat and electricity, generally shiny, solid at room temperature, malleable and ductile.

Non-Metals are elements that are poor conductors of electricity and heat and generally gases and brittle solids.

Metalloids are elements that exhibit some properties of metals and some properties of non-metals.

The elements in the periodic The elements in the periodic table divided into groups table divided into groups namely:namely:

1.1. Main-group (representative) Main-group (representative) elementselements

2.2. Transition elementsTransition elements3.3. Inner transition elementsInner transition elements

Main Group (Representative

Elements)

Alkali Metals (Li, Na, K, Rb, Cs, Fr)The alkali family is found

in the first column of the periodic table.

Alkali metals are found in Group 1A or 1

Atoms of the alkali metals have a single electron in their outermost level, in other words, 1 valence electron.

Alkali Metals They are the most reactive metals.

They react with water to release hydrogen gas.

Alkali metals are never found as free elements in nature. They are always bonded with another element.

Alkaline Earth Metals (Be, Mg, Ca, Sr, Ba, Ra)

They are found in Group IIA or 2 They have two valence electrons.They are very reactive, but not as much as

the alkali metals.

Boron FamilyThe Boron Family is

named after the first element in the family.

They are found in Group IIIA or 13.

Atoms in this family have 3 valence electrons.

B, Al, Ga, In, Tl are the elements belong to the group.

Carbon FamilyAtoms of this family

have 4 valence electrons.

They found in Group IVA or 14.

This family includes C, Si, Ge, Sn, Pb

Nitrogen Family The nitrogen family is

named after the element that makes up 78% of our atmosphere.

They can be found in Group VA or 15

Atoms in the nitrogen family have 5 valence electrons. They tend to share electrons when they bond.

Other elements in this family are phosphorus, arsenic, antimony, and bismuth.

Oxygen Family Atoms of this family have

6 valence electrons. They belong to Group VIA

or 16. Most elements in this

family share electrons when forming compounds.

This family includes S, Se, Te, Po

Halogen FamilyThe elements in

this family are fluorine, chlorine, bromine, iodine, and astatine.

They can be found in Group VIIA or 17.

Halogens have 7 valence electrons.

They react with alkali metals to form salts.

Transition Metals Transition Elements

include those elements in the B families.

These are the metals you are probably most familiar: copper, tin, zinc, iron, nickel, gold, and silver.

They are good conductors of heat and electricity.

Transition Metals

The compounds of transition metals are usually brightly colored and are often used to color paints.

Transition elements have 1 or 2 valence electrons, which they lose when they form bonds with other atoms.

Noble Gases

Noble Gases are colorless gases that are extremely un-reactive.

One important property of the noble gases is their inactivity. They are inactive because their outermost energy level is full.

Because they do not readily combine with other elements to form compounds, the noble gases are called inert.

The family of noble gases includes helium, neon, argon, krypton, xenon, and radon.

All the noble gases are found in small amounts in the earth's atmosphere.

Rare Earth ElementsThe thirty rare earth

elements are composed of the lanthanide and actinide series.

One element of the lanthanide series and most of the elements in the actinide series are called trans-uranium, which means synthetic or man-made.

Electron Configurations and the Electron Configurations and the Periodic TablePeriodic Table

Elements belonging to the same group have the same number of valence electrons.

Elements belonging to the same period have the same number of shells.

The s, p, d and f blocks of The s, p, d and f blocks of elementselements

Elements are easily differentiated from one another because of differences in the number of their outermost electrons.

The first 2 columns to the right of the periodic table fill up the nsns orbitals and are referred to as s-block elements.

o The last 6 columns fill up the np np orbitals and are called the p-block elements.

o Between the s-block and the p-block elements are 10 columns which fill up the (n-1)d orbitals. These are the d-block elements.

o On the lower part of the Periodic Table are two series of elements which fill up the (n-2) f orbital and are called the f-block elements.

Predicting Periods and GroupsPredicting Periods and GroupsThe period and groups of an element

can be predicted from the electron configuration of that element.

The following guidelines can help in determining the period and group of an elements.

If the electron configuration of the element ends in s or p, then the element belongs to family A; otherwise, the element belongs to family B.

The outermost energy of the element corresponds to its period.

For an element belonging to family A, the number of electrons in the outermost energy level corresponds to the group of the elements.

For an element belonging to B (provided that the electron configuration does not end in f the total number of electrons in the outermost energy in level and the incomplete inner sub-level is equal to the group number except for the following sums whose corresponding groups are indicated.

Practice Exercise:

Noble Gas Core NotationThis is the shorthand way of writing

the electronic configuration of an element.

The noble gas that precedes a given element is called the core element of the given element.

Steps in Writing the Noble Gas Notation:

1. Put symbol for noble gas from the previous row in brackets.

2. Start at the beginning of the row where the element is located.

3. Move to the right, writing down any sublevels (blocks) that you move through.

Practice Exercise:

Trends in the Trends in the Periodic TablePeriodic Table

Periodic Trends are specific patterns that are present

in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties.

1. Atomic Size Usually expressed as an atomic

radius measured in picometers. Atomic radius is equal to half the

distance between the nuclei of two atoms of the same element when they are joined.

Atomic size increases as you move down a group.

Going down a row adds another energy level of electrons.

Atomic sizes decreases as you move from left to right across a period.

Moving from left to right there is an increase in protons causing greater attraction to electrons.

2. Ionization Energy is the energy required to remove

an electron from an atom.

Shielding Effect -- when inner electrons block the

positive charge from outer electrons.

Ionization energy tends to decrease down a group in the periodic table.

The farther, the distance of an electron from the nucleus the more easily it can be removed.

Ionization energy tends to increases from left to right across a period.

Atoms with fewer electrons hold on to the more tightly.

3. Electronegativity is the ability of an atom to attract

electrons to itself.Electronegativity decreases from

top to bottom and increases from left to right of the periodic table.

4. Electron Affinity is the amount of energy released or

exerted when an atom gains an electron.

The electron affinity of an atom can be described either as the energy gained by an atom when an electron is added to it.

Down a group the electron affinity of the elements decreases.

Electron Affinity increases within a period.

5. Metallic Property Within a period of the periodic

table, the elements become more nonmetallic from left to right across a series.

Within a group or from top to bottom metallic properties increase.

Periodic Propert ies of the elements

Electron affinity

Ionization energy

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Atomic radius

Nonmetallic character

metallic character

Atomic properties and the periodic table a summary

Atomic Properties