Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Question:
Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $\mathrm{R}$.
Assertion $\mathrm{A}: \mathrm{In} \mathrm{TII}_{3}$, isomorphous to $\mathrm{CsI}_{3}$, the metal is present in $+1$ oxidation state.
Reason R: TI metals has fourteen $f$ electrons in its electronic configuration.
In the light of the above statements, choose the most appropriate answer from the options given below:
Correct Option: , 3
Solution:
$\mathrm{T} \ell \mathrm{I}_{3}$ is $\mathrm{T} \ell^{+} \mathrm{I}_{3}^{-}$
$\mathrm{CSI}_{3}$ is $\mathrm{Cs}^{+} \mathrm{I}_{3}^{-}$
Thallium shows $\mathrm{T} \ell^{+}$state due to inert pair effect.