The stable bivalency of $\mathrm{Pb}$ and trivalency of $\mathrm{Bi}$ is

The stable bivalency of $\mathrm{Pb}$ and trivalency of $\mathrm{Bi}$ is
  1. due to $d$ contraction in $\mathrm{Pb}$ and $\mathrm{Bi}$
  2. due to relativistic contraction of the $6 s$ orbitals of $\mathrm{Pb}$ and $\mathrm{Bi}$, leading to inert pair effect
  3. due to screening effect
  4. due to attainment of noble liquid configuration

Solution

$_{82} \mathrm{Pb}=6 \mathrm{s}^{2} 6 p^{2}$
$_{83}{\mathrm{Bi}}=6 s^{2} 6 p^{3}$
Due to inertness of $6 s^{2}$ electrons in $\mathrm{Pb}$ and $\mathrm{Bi}$, they show bivalency and trivalency respectively instead of tetra and pentavalency.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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