Question

The stable bivalency of $Pb$ and trivalency of $Bi$ is :

• A. due to d contraction in $Pb$ and $Bi$
• B. due to relativistic contraction of the $6s$ orbitals of $Pb$ and $Bi$, leading to inert pair effect
• C. due to screening effect
• D. due to attainment of noble liquid configuration

Answer 1

The correct option is B due to relativistic contraction of the $6s$ orbitals of $Pb$ and $Bi$, leading to inert pair effect


83Bi=6s26p3${Pb=6s}^2{6p}^2{Bi=6s}^2{6p}^3$

Due to inertness of $6s^2$ electrons in PbPb and BiBi, they show bivalency and trivalent respectively instead of tetravalent and pentavalency.