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 molecules are identical.

(i) Due to lack of empty d-orbitals in nitrogen, it does not form pentahalide
(ii) Due to small size, fluorine atom has high electronegativity and strong electron-electron repulsion in its compact 2p orbitals. Its electron gain enthalpy is less than that of chlorine due to less electron-electron repulsion in chlorine
(iii) The O – O distances are 127.2 pm (1.272 Å). The O – O – O angle is 116.78°. The central atom is sp² hybridized with one lone pair. The bonding can be expressed as a resonance hybrid with a single bond on one side and double bond on the other producing an overall bond order of 1.5 for each side.