Discuss the pattern of variation in the oxidation state of C to Pb.
C and Si do not exhibit inert pair effect due to the absence of d-or f-electrons. As a result, they show an oxidation state of +4 only due to the presence of two electrons in the s-and two electrons in the p-orbital of the valence shell.
On the other hand, the elements from Ge to Pb contain the only d- and f-electrons and hence show oxidation state of +2 and +4 due to inert pair effect. Further, as we move down the group, the number of d-and f -electrons increases and consequently the inert pair effect becomes more and more pronounced. In other words ns2 electron pair in Ge, Sn and Pb tends to remain paired, thus stability of +2 oxidation state increases while that of +4 oxidation state decreases. Thus +2 oxidation state of Pb is more stable than its +4 oxidation state.
