1.

Discuss the pattern of variation in the oxidation states of (i) B to Tl (iii) C to Pb.

Answer»

Solution :(i) B and Al have no d-or f-electrons. THEREFORE, they do notexhibit inert pair effect.Consequently,they slow show an oxidationstate of +3 only due to th persenceof two electrons in the s-and one electronin the p-orbitalof the valenceshell. In CONTRAST, all otherelement from Ga TOTL contains eitheronly d-ord- and f-electronsand henceshow two oxidationstatesof +1 and +3 due to inert pair effect.Further, as the numberof d- and f-electrons increasesdown te group , the inert pair effect becomes more and more pronounced. In other words, as wemove downthe groupfrom Ga to Tl, the stability of +1 oxidation state increases(i.e,`Ga ltln lt Tl`) while that of +3 oxidationstate decreases(i.e.,`Ga lt ln gt Tl`). Thus,`+I` oxidationstate ofTl is more STABLETHAN its +3 oxidationstate.
(ii) Carbonand siliconhave no d-or f-electrons.Therefore , they do not exhibitinert pair effect.
Consequentlytheyshowan oxidationstateof +4 dueto the presence of two electrons in the s- and two electronsin the p-orbital of the valenceshell. In contrast , all other elemen from Ge to Pb contain eitheronly d- or f-electronand hence show two oxidationstates of +2 and +4 due toinertpair effect.
Further , as the number of d- and f-electronsincreases , the inertpair effectbecomesmoreand morepronounced. In otherwords,as wemore downthe groupfrom Ge to Pb,the stability of +2 oxidationstate increases (i.e., `Ge lt Sn lt Pb`) while thatof `+4`oxidationstatedecreases (i.e., `Ge gt Sn gt Pb`).
Thus, +2 oxidationstate of Pb is more stable than its +4 oxidation state.


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