Give reasons for the following :
(i) Though nitrogen exhibits + 5 oxidation state, it does not form pentahalide.
(ii) Electron gain enthalpy with negative sign of fluorine is less than that of chlorine.
(iii) The two oxygen-oxygen bond lengths in ozone molecule are identical.

Explanation

(i) Nitrogen does not have vacant d-orbitals in its valence shell. Therefore, it cannot extend its valency beyond 3.
(ii) Most of the highest oxidation state metal halides are fluorides eg. `Pb F_(5), VF_(5), BiF_(6)` Corresponding chlorides are either unstable or unknown. This shows stronger oxidising power of `F_(2).`
(iii) The structure of ozone molecule is angular as in the given figure. The O - O - O bond angle is `116.8^(@)` and O - O bond length is 127.8 pm

The bond length in ozone molecule is intermediate between single and double bond in oxygen atom. Ozone molecule thus, is considered to be a resonance hybrid of these figure