Question

What are the various factors due to which the IE of the main group elements tends to decrease down a group?

Answer 1

The factors which makes IE decreasing down the group are -

$\mathsf \red{1. \: Atomin \: radius \:( or) \: Atomic \: Size :}$

Larger is the atomic size smaller is the ionization enthalpy. As the atomic radius increases the nuclear force of attraction over the valency electrons decreases the relation is

$\: \: \: \: \: \: \: \: \: \: \: \boxed{ \mathsf \red{Ionization \: enthalpy \propto \: \frac{1}{Atomic \: size} }}$

$\mathsf \red{2. \: screening \: effect \: ( or ) \: shielding \: effect : \: }$

Higher the screening effect, the lesser is the value of ionization enthalpy. It reduces the force of attraction towards nucleus. Hence outermost electrons can be easily removed

$\: \: \: \: \: \: \: \: \: \: \: \boxed{ \mathsf \red{Ionization \: enthalpy \propto \: \frac{1}{Screening effect} }}$