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Discuss the pattern of variation in the oxidationstates of (i) B to Tl and (ii) C to Pb. |
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Answer» Solution :(i)B to Tl :The electric configuration of group 13 elements is `ns^2np^1`.Therefore , the most common oxidation state exhibited by them should be +3. However, it is only boron and aluminium which practically show the +3 oxidation state. The remaining elements i.e., GA,In, Tl , Show both the +1 and +3 oxidation states . On moving down the group , the +1 statebecomes more stable . For example ,Tl(+1) is more stable than Tl (+3). This is because of the inert pair effect. The two electrons present in the s-shell are strongly attracted by the nucleus and do not participate in bonding . This inert pair effect BECOMES more andmore prominenton movingdown the group. Hence,Ga(+1) is unstable , In (+1) is fairly stable and Tl (+1) is very stable.  The stability of the +3oxidationstate decreases on moving down the group. (II)C to Pb : The electronic configuration of group 14 elements is `ns^2 np^2`. Therefore , the most common oxidationstate exhibited by them should be +4. However, the +2 oxidation state becomes more and more common on moving down the group . C and Si mostly show the +4 state. On moving down the group, the HIGHER oxidation state becomes LESS stable. This is because of the inert pair effect. Thus, although Ge, Sn and Pb show both the +2 and +4 states, the stability of the lower oxidation state increases and that of the higher oxidation state decreases on moving down the group. 
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