question_answer

C and Si are almost always tetravalent but Ge, Sn and Pb show divalency. Why? Or Why the tendency to exhibit + 2 oxidation state increases with increasing atomic number in group 14. Or +2 oxidation state of lead is more stable than +4 oxidation state. Give reasons.

Answer:

                Among the elements of group 14, carbon does not have d- or f-electrons. Therefore, it does not show inert pair effect. Consequently, it shows an oxidation state of +4 due to the presence of two electrons is the s- and two electrons in the p-orbital of the valence shell. In contrast, all other elements from Ge to Pb contain either d or both d- and f-electrons and hence show oxidation states of + 2 and + 4 due to inert pair effect. Further, as the number of d-and f-electrons increases, the inert pair effect becomes more and more prominent. In other words, as we move down the group from Ge to Pb, the stability of +2 oxidation state increases while that of +4 oxidation state decreases. Therefore, the tendency of Ge, Sn and Pb to exhibit + 2 oxidation state increases with increasing atomic number in group 14.