Question

Carbon and silicon are tetravalent but Ge, Sn and Pb show divalency also.

Answer 1

All these elements belong to sub group IV A. Characteristic of inert pair effect is found in this IV A subgroup elements. Downward elements after Si have less stability by 4 than oxidation state 4 and stability is increased of elements having +2 oxidation state. Where Ge(+4) is stable. In this way Sn(+2) is simple ionic and reducing agent, whereas Sn(+4) is co-ordinator. Half diameter of M²⁺ is greater than M⁺⁴. So, compounds of radical having less valency are more ionic.