p Block Elements (Group 1 question bank (Chemistry)

Consider the following reactions.
$\mathrm{PbCl}_{2}+\mathrm{K}_{2} \mathrm{CrO}_{4} \rightarrow \mathrm{~A}+2 \mathrm{KCl}$
(Hot solution)
$\mathrm{A}+\mathrm{NaOH} \rightleftharpoons \mathrm{B}+\mathrm{Na}_{2} \mathrm{CrO}_{4}$
$\mathrm{PbSO}_{4}+4 \mathrm{CH}_{3} \mathrm{COONH}_{4} \rightarrow\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}+\mathrm{X}$
In the above reactions, $\mathrm{A}, \mathrm{B}$ and X are respectively.

The group 14 elements A and B have the first ionisation enthalpy values of $708$ and $715 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. The above values are lowest among their group members. The nature of their ions $\mathrm{A}^{2+}$ $\mathrm{B}^{4+}$ respectively is