How would you account for the following ?
(i)The lower oxidation state becomes more stable with increasing atomic number in Group 13.
(ii)Hydrogen fluoride is much less volatile than hydrogen chloride.
(iii)Interhalogen compounds are strong oxidising agents.

Answer

(i)The outer electronic configuration of group 13 elements is `ns^(2)np^(1)`.On moving down the group, due to inert pair effect, there is a decrease in the tendency of s electrons of the valence shell to participate in bond formation.This is due to the poor shielding of the `ns^(2)` electrons of the valence shell by the intervening d or f electrons.So, only the p electrons can participate in bonding.Hence, the oxidation state is restricted to +1 only.
(ii)Fluorine is more electronegative than chlorine.Therefore, HF undergoes stronger H-bonding than HCl. Hence, HF is much less volatile than HCl.
(iii)Halogens are very electronegative so they act as strong oxidising agents.In interhalogen compounds. X-X' bond is very weak and can be easily broken.As a result, interhalogen compounds also act as strong oxidising agents.