Three pairs of compounds are given below. Identify that compound in each of the pairs which has group $-13$ element in more stable oxidation state. Give reason for your choice. State the nature of bonding also. $(A)$ $TlCl_3, TlCl$ $(B)$ $AlCl, AlCl$ $(C)$ $InCl_3, InCl$

$(A)$ $\mathrm{TlCl}$ is more stable than $\mathrm{TlCl}_{3}$ because moving down the group lower oxidation state is more stable due to inert pair effect.

$(B)$ $\mathrm{AlCl}_{3}$ is more stable because it does not show inert pair effect. It is a covalent compound and acts as a Lewis acid

$(C)$ $\mathrm{InCl}$ is more stable due to inert pair effect and lower oxidation state $+1$ is more stable. In shows both the oxidation states $+3$ and $+1$.

$3 \mathrm{InCl}_{\text {(aq) }} \rightarrow 2 \mathrm{In}_{\text {(s) }}+\mathrm{In}_{\text {(aq) }}^{3+}+3 \mathrm{Cl}_{\text {(aq) }}^{-}$