Q17 / 160 · WBJEE 2012 · Chemistry

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

  • A
    due to $d$ contraction in $\mathrm{Pb}$ and $\mathrm{Bi}$
  • Correct answer
    B
    due to relativistic contraction of the $6 s$ orbitals of $\mathrm{Pb}$ and $\mathrm{Bi}$, leading to inert pair effect
  • C
    due to screening effect
  • D
    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.

Hence, the correct answer is option: 'B'.

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