Given reasons for the following:(i) When R is an alkyl group, R3P=O exists but R3N=O doesn't.(ii) PbCl4 is more covalent than PbCl2.(iii) N2 is much less reactive at room temperature.

(i) Nitrogen lacks the d orbital so nitrogen cannot expand its coordination number beyond four so R3N=O does not exist (ii) According to Fazan's rule, a higher charge on cation or anion makes compound more covalent, +4 state is more stable then +2 state. Hence PbCl4 is more covalent than PbCl2 (iii) Dinitrogen is formed by sharing three electron pairs between two nitrogen atoms. The two nitrogen atoms are joined by triple bond (N≡N). The nitrogen atom is very small in size, therefore the bond length is also quite small (109.8 pm) as a result the bond dissociation energy is quite high (946 Kj/mol). This reason leads dinitrogen to be very less reactive at room temperature.