It's provide all details and properties of periodic table like electronegativity and atomic radius that affect the chemical and physical properties of an element

1. 1
THE PERIODIC TABLE
A listing of elements in an array such that
atomic numbers increase from left to right
and elements in any column have similar
outer electronic structures.
ROWS = PERIODS
COLUMNS = GROUPS

2. 2
CLASSES OF ELEMENTS
1. REPRESENTATIVE ELEMENTS
The differentiating electrons fill the s and p
orbitals, Groups IA-VIIA and Group O. These are
sometimes called MAIN GROUP ELEMENTS
2. TRANSITION ELEMENTS
The differentiating electrons fill d-orbitals.
3. INNER TRANSITION ELEMENTS
Differentiating electrons fill the f-orbitals
4f - Lanthanides
5f - Actinides

3. 3
PERIODIC PROPERTIES
1. ATOMIC RADIUS
2. IONISATION ENERGY
3. ELECTRON AFFINITY
4. ELECTRONEGATIVITY

4. 4
ATOMIC RADIUS
nm
0.099
2
0.198
Radius
Atomic
Cl2 

Definition: This is one half the distance between centers of
touching atoms.
r
TRENDS:
(i) Decreases as we move across a period from left to right in the PT.
(ii) Increases as we move down a Group in the PT.

5. 5
RATIONALE:
Across a Period
Effective nuclear charge experienced by an electron at the outer
edge of an atom is given by:
Zeff = Z – S
Where: Z = Actual nuclear charge = At. No.
S = No. of electrons between the outer electron and the
nucleus.
For main group elements
S = No. of electrons in inner complete energy levels.
e.g. for Mg with 1s2 2s2 2p6 3s2 then S = 10.
Therefore:
Zeff should increase as we move across a period from left to right in
the PT.
RESULT Atomic radius decreases from left to right of PT.

6. 6
Down the Group:
 Down the Group, Zeff experienced by an outer electron
remains essentially constant.
 However, the distance of the electron from the nucleus
increases with the Principal Quantum Number.
At. No. S Zeff
H = 1s1 1 1
Li = 1s2 2s1 3 2 1
Na = 1s2 2s2 2p6 3s1 11 10 1
K = 1s2 2s2 2p6 3s2 3p6 4s1 19 18 1
 Hence: Atomic Radius increases as we move down the
Group in the PT.

7. 7
FIRST IONISATION ENERGY
Definition:
 The energy that must be absorbed to remove the outermost
electron from a gaseous atom.
Mg(g)  Mg+
(g) + e-
TRENDS:
i. Increases as we move across a period (from LEFT to RIGHT)
in the Periodic Table.
ii. Decreases as we move down a Group in the Periodic Table.
There are some exceptions:
e.g. 1st ionization Energy actually decreases as one moves across
from Be (900 kJ/mol) to B (801 kJ/mol).
Be = 1s2 2s2
B = 1s2 2s2 2p1
Since 2p level is higher in Energy than 2s
it easier to remove an electron from 2p

8. 8
Ionization energy does not increase smoothly as we remove
successive electrons
e.g. Na: 1s2 2s2 2p6 3s1
IE1 = 496 kJ/mol. From 3s and hence removed easily since
it is far from the nucleus.
IE2 = 4561 kJ/mol.
IE3 = 6913 kJ/mol
ANY COMMENT ON THE TREND?

9. 9
ELECTRON AFFINITY
Definition: The energy change that occurs when an electron is
added to a gaseous atom or ion.
i.e. (i) M(g) + e-  M-
(g) [Neutral atom]
(ii) M+
(g) + e-  M(g) [an ion of charge +1]
TRENDS:
(i) Across a Period
In general electron affinities become more negative (stronger
attraction for an electron) from LEFT to RIGHT of the PT.

10. 10
(ii) Down a Group:
Electron affinities differ very little as we go down a group.
REASONS
• Average distance of electron from nucleus steadily
increase, and electron-nuclear attraction should steadily
decrease.
• Orbitals become increasingly spread out and electron-
electron repulsion with the added electron decreases.
 These two factors counterbalance.

11. 11
ELECTRONEGATIVITY
Definition:
The ability of an atom to attract electrons to itself in a
chemical bond.
TRENDS:
(i) Increases as we move across a Period from LEFT to
RIGHT. i.e. From the most metallic to the most non-
metallic element.
(ii)Decreases as we move down a group (excluding a few
exceptions)
i.e. From the most non-metallic to the most metallic
element.

12. 12
NOTE:
Electronegativity varies with the TYPE of chemical environment in which
an element is in.
Eg. Chlorine : in PCl3 or in ClO3
-
The electronegativity difference between two atoms is a measure of the
polarity of the bond between them:
The greater the difference in electronegativity, the more polar is the bond.
Most electronegative element : F = 4.0
Least electronegative element : Cs = 0.79
e.g. HF  H+  F-
H  electronegativity = 2.2}
F  electronegativity = 4.0}
Therefore H-F is a POLAR BOND