Discuss the pattern of variation in the oxidation states of C to Pb.

Explanation

Carbon and silicon have no d - or f-electrons and hence do not exhibit inert pair effect. As a consequence, they exhibit an oxidation state of +4 due to presence of two electrons in the s-and two electrons in the p -orbital of the valence shell. In contrast, the remaining elements Ge, Sn and Pb contain only d - or both d -and f-electrons and hence show two oxidation states of +2 and +4 due to inert pair effect that becomes more and more pronounced with the increasing number of d -and f-electrons . In other words, on moving down the group from Ge to Pb, the stability of +2 oxidation state increases (i.e., Ge < Sn< Pb) while that of +4 oxidation state decreases (i.e., Ge> Sn > Pb) . In fact, the +2 state is more stable than its +4 state.