(a) Though nitrogen exhibits `+5` oxidation state, it does not form pentahalide. Give reason.
(b) `PH_3` has lower boiling point than `NH_3`. Why ?

Explanation

The atomic number os notrogen is 7. Its electronic configuration is `1s^(2)2s^(2)2p^(3).` As notrogen has no d-orbitals in its valence shell, it cannot undergo `sp^(3)d` hybridization and hence cannot form pentahalides.