How would you account for the following :
(i) The electron gain enthalpy with negative sign is less for oxygen than that for sulphur.
(ii) Phosphorus shows greater tandency for catenation than nitrogen.
(iii) Fluorine never acts as the central atom in polyatomic interhalogen compounds.

Explanation

(i) Because of the compact nature of oxygen atom oxygen has less negative electron gain enthalpy than sulphur.
(ii) It is due to weaker N-N bond than P-P bond due to more repulsion between valence `e^(-)s` of nitrogen (smaller in size) than phosphorus.
(iii) It is becuase `F` does not have vacand d-orbitals and cannot show positive and higher oxidalion state.