JEE Main 2021 — Chemistry Inorganic Chemistry

2021mcqmedium

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$ .

Assertion $A:$ In $Tl{I}_{3},$ isomorphous to ${\mathrm{CsI}}_{3}$ , the metal is present in $+1$ oxidation state.

Reason $R:$ $Tl$ metal 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:

Official previous-year question

Held on 26 Feb 2021 · Verified 6 Jul 2026.

Options

A
$A$ is correct but $R$ is not correct
B
Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$
C
$A$ is not correct but $R$ is correct
D
Both $A$ and $R$ are correct but $R$ is $\mathrm{NOT}$ the correct explanation of $A$

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Solution

$T\ell {I}_{3}\Rightarrow (T{\ell }^{\oplus }&{I}_{3}^{\circleddash })$

${\mathrm{CsI}}_{3}\Rightarrow ({\mathrm{Cs}}^{\oplus }&{I}_{3}^{\circleddash })$

[Both have same crystalline structure is called isomorphous]

$T{\ell }_{(81)}^{\oplus }=[{\mathrm{Xe}}_{54}]4{f}^{14},5{d}^{10},6{s}^{2}$

(It is correct due to present $14f$ electrons in ${T\ell }^{\oplus }$ ion)

$Tl{I}_{3}$ is $T{\ell }^{+}{I}_{3}^{-}$

${\mathrm{CSI}}_{3}$ is ${\mathrm{Cs}}^{+}{I}_{3}^{-}$

Thallium shows $T{\ell }^{+}$ state due to inert pair effect.

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Solution

$T\ell {I}_{3}\Rightarrow (T{\ell }^{\oplus }&{I}_{3}^{\circleddash })$

${\mathrm{CsI}}_{3}\Rightarrow ({\mathrm{Cs}}^{\oplus }&{I}_{3}^{\circleddash })$

[Both have same crystalline structure is called isomorphous]

$T{\ell }_{(81)}^{\oplus }=[{\mathrm{Xe}}_{54}]4{f}^{14},5{d}^{10},6{s}^{2}$

(It is correct due to present $14f$ electrons in ${T\ell }^{\oplus }$ ion)

$Tl{I}_{3}$ is $T{\ell }^{+}{I}_{3}^{-}$

${\mathrm{CSI}}_{3}$ is ${\mathrm{Cs}}^{+}{I}_{3}^{-}$

Thallium shows $T{\ell }^{+}$ state due to inert pair effect.

JEE Main 2021 — Chemistry Inorganic Chemistry

Options

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Solution

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JEE Main Inorganic Chemistry in other years

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JEE Main 2021 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry