[shirleyisgood]

what is inert pair effect actually?Why Pb shows prominent ienrt pair effect?
thanks.

[Schrödinger]

http://en.wikipedia.org/wiki/Inert_pair_effect

[juanrga]

what is inert pair effect actually?Why Pb shows prominent ienrt pair effect?
thanks.

The inert pair effect is the reluctance of s-electrons to take part in bond formation. A chemical consequence is the occurrence of oxidation states which are two units less than the group oxidation. For instance the more stable Pb state is Pb(II), with Pb(IV) being particularly unstable (e.g. the reduction PbCl₄ PbCl₂ is easy).

The underlying explanation is a quantum relativistic effect: the 6s² electrons resist oxidation due to a relativistic contraction of the 6s orbital which tends to draw the electrons closer to the nucleus than you would expect. Because they are closer to the nucleus, they are more difficult to remove. The heavier the element, the greater this effect {*}.

{*} In general, quantum relativistic effects are more stronger for heavy atoms.

[shirleyisgood]

thx~i got it~