Discuss the pattern of variation in the oxidation states of

(i) B to Tl

(ii) C to Pb.

(i) Group 13 elements have their electronic configuration of ns² np¹ and the oxidation state exhibited by these elements should be 3. Apart from these two electrons boron and aluminum, other elements of this group exhibit both + 1 and + 3 oxidation states. Boron and aluminum show oxidation state of + 3. This is because of the inert pair effect. The two electrons, which are present in the S-shell do not participate in bonding as they are strongly attracted by the nucleus. As we move down the group, the inert pair effect become more prominent. Therefore Ga ( + 1) is unstable and TI ( + 1) is very stable

On moving down the group, the stability of the + 3 oxidation state gets decreased.

(ii) The electronic configuration of group 14 elements is ns² np². Hence, the most common oxidation state exhibited by them should be + 4. On moving down the group, the + 2 oxidation state becomes more and more common and the higher oxidation state becomes less stable because of the inert pair effect. Si and C mostly show the + 4 state. Although Sn, Ge, and Pb show both the + 4 and + 2 states, the stability of higher oxidation states decreases than lower oxidation state on moving down the group.