Question

Which of following stability order is /are correct due to inert pair effect?

• A. $H{g}^{\circ }>H{g}^{2+}$
• B. $B{i}^{3+}<B{i}^5$
• C. $P{b}^{2+}>P{b}^{4+}$
• D. $F{e}^{2+}<F{e}^{3+}$

Answer 1

Answer: (A), (C)

$H{g}^{\circ }>H{g}^{2+}$
$P{b}^{2+}>P{b}^{4+}$

The inertness of s subshell electrons towards the bond formation is called inert pair effect or it can be said as the inactiveness of electrons present in outermost shell (i.e. $n{s}^2$) to get unpaired and involve in bond formation is called inert pair effect.

for example:

1) In 13th group, thallium can exhibit $+1$ and $+3$ oxidation states but it is stable in $+1$ oxidation state only due to inert pair effect

2) In 14th group , lead shows both $+2$ and $+4$ oxidation states but it is stable in $+2$ oxidation state due to inert pair effect.

3)In group 15 elements, the stability of $+3$ oxidation state increases down the group and that of $+5$ oxidation state decreases down the group, due to inert pair effect."