why in p-block elements the lower oxidation states are favoured by heavier metals? also explain inert pair effect

Asked by Anushri | 6th Jul, 2013, 11:30: AM

Expert Answer:

The inert pair effect, is the tendency of the outermost s electrons to remain unionized or unshared in compounds of post-transition metals. The term inert pair effect is often used in relation to the increasing stability of oxidation states that are 2 less than the group valency for the heavier elements of groups 13, 14, 15 and 16.

When we go down in p-block elements we can see the succesive elements have an increased d or f- shell. This d or f shell cause the inert pair effect. Actually the mentioned shells have a weak sheilding effect of nuclear charge so the nuclear charge easily attracts the electrons in the outer shells than the d or f shells. This makes the electrons in the outer shells become unable to participate the reactions taking place. This makes them inert hence the name inert pair effect.

The tendency of ns2 electron pair to participate in bond formation decreases with the increase in atomic size. Within a group the higher oxidation state becomes less stable with respect to the lower oxidation state as the atomic number increases. 

We can see this in case of Pb. Pb has f shell which has a very low shielding capacity and it has 4 electrons in outer most shell but due to this effect Pb is more stable showing +2 valency state.

Answered by  | 8th Jul, 2013, 01:08: AM

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