(a) Account for the following:
(i) Acidic character increase from HF to HI.
(ii) There is a large difference between melting and boiling points of oxygen and sulphur.
(iii) Nitrogen does not form pentahalide.
(b) Draw the structures of the following:
(i) ClF3
(ii) XeF4

a (i) The acidic strength of the hydrohalic acids increase from HF because the stability of the acids decrease from HF to HI on account of decrease in bond dissociation enthalpy of H−X bond from HF to HI (ii) The difference in melting point and boiling point of oxygen and sulphur is due to the difference in their atomicities, oxygen exists as a diatomic (O2) molecule, while sulphur exists as a polyatomic (S8) molecule and also oxygen is small in size and have high electro-negativity (iii) Being an element of second period, Nitrogen has no 'd' orbitals and its maximum covalency is restricted to four. Hence, due to the non-availability of d-orbitals, it can't form pentahalides.