IMPORTANT COMPONENTS OF THE MODERN PERIODIC TABLE -

Standard

ATOMIC SIZE, METALLIC CHARACTER, NON-METALLIC CHARACTER, IONIZATION POTENTIAL,ELECTRON AFFINITY,ELECTRONEGATIVITY& THEIR

some importent topic of chemistry

DEFINITION, EXPLANATION & VARIATION

ATOMIC SIZE -It is the distance between the center of the nucleus of atomo and its outer most shell. It is also called atomic radius. Unit of atomic radii

is A

[Angstrom unit] 1A*=10 to the power –10m. Atomic size depends on 2 factors-

{i} NUMBER OF SHELLS{ii}NUCLEAR CHARGE

NUMBER OF SHELLS-Increase in the number of shells increases atomic size as distance between the outermost shell & nucleus increases.

NUCLEAR CHARGE-Increase in the nuclear charge of an atom decreases atomic size as the electrons in the outer most shell are attracted towards the nucleus with a

greater force.

VARIATION:-IN A GROUP -the size of atom increases as one moves from top to bottom due to successive addition of shells as one moves from one period to the

next.

VARIATION:-IN A PERIOD -the size of atom decreases from left to right as nuclear charge increases.

, METALLIC CHARACTER -The elements which have a tendency to lose their valence electrons and form a positive ion are said to exhibit metallic character. It

depends on atomic size & nuclear charge.

The force of attraction decreases when atomic size increases so elements become more metallic in nature & when nuclear charge increases force exerted by nucleus

increases so elements become less metallic in nature.

VARIATION:- IN A GROUP- metallic character increases as one moves down a group

VARIATION:-IN A PERIOD– metallic character decreases from left to right.

, NON-METALLIC CHARACTER – The elements which have a tendency to gain electrons and form negative ion are said to exhibit non-metallic character. It depends

on atomic size & nuclear charge.

The force of attraction increases when atomic size decreases so elements become more non-metallic in nature & the tendency to gain electrons increases when

nuclear charge increases so elements become more non-metallic in nature.

VARIATION:- IN A GROUP—non-metallic character decreases as one moves down a group

VARIATION:-IN A PERIOD—non-metallic character increases from left to right in a period.

IONIZATION POTENTIAL -It is the amount of energy required to remove the most loosely bound electron from an isolated neutral gaseous atom and convert it into

a positively charged ion. It is measured in volts per atom[eV/atom] & its S.I. unit is kilo joule/mole[kJ/mole]. It depends on 2 factors:- atomic size & nuclear charge

The force of attraction decreases when atomic size increases & the force of attraction increases when nuclear charge increases

VARIATION:- IN A GROUP—Ionization potential decreases as one moves down a group as atomic size increases.

VARIATION:-IN A PERIOD— Ionization potential increases from left to right in a period.as atomic size decreases & nuclear charge increases.

. ELECTRON AFFINITY-The amount of energy released while converting a neutral gaseous atom into a negatively charged ion [anion] is called electron affinity.

It depends on 2 factors:- atomic size & nuclear charge.

If the size of atom decreases electron affinity increases & if nuclear charge increases electron affinity increases.

VARIATION:- IN A GROUP—electron affinity decreases as one moves down a group as atomic size increases than nuclear charge.

VARIATION:-IN A PERIOD— electron affinity increases from left to right in a period.as atomic size decreases & nuclear charge increases..

,ELECTRO NEGATIVITY- It is the tendency of an atom in a molecule to attract the shared electron pair towards itself.

It depends on 2 factors: – atomic size & nuclear charge.

If the size of atom increases electro negativity decreases & if nuclear charge increases electro negativity increases.

VARIATION:- IN A GROUP— electro negativity decreases as one moves down a group as the effect of increase in atomic size is overcomes the effect of increase of

nuclear charge.

VARIATION:-IN A PERIOD— electro negativity increases from left to right in a period as nuclear charge increases due to increase in atomic number.

Referred to this material  by Administrator of : Online Education Guide