what is inert pair effect????
The inertness of s subshell electrons towards the bond formation is called inert pair effect or it can be said as the inactiveness of electrons present in outermost shell (i.e. ns2) to get unpaired and involve in bond formation is called inert pair effect.
for example:
1) In 13th group, thallium can exhibit +1 and+3 oxidation states but it is stable in +1 oxidation state only due to inert pair effect
2) In 14th group , lead shows both +2 and +4 oxidation states but it is stable in +2 oxidation state due to inert pair effect.
or
Inert pair effect may be defined as inertness of inner ns sub-shell towards chemical reaction. It is seen in groups 3A and 4A especially (5s and 6s electrons). Therefore Pb shows mainly +2 oxidation state frequently as compared to +4 oxidation state.
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