Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The stability order of +1 oxidation state of Ga , In and Tl is Ga < In < Tl . Reason (R): The inert pair effect stabilizes the lower oxidation state down the group. In the light of the above statements, choose the correct answer from the options given below :

Both (A) and (R) are true and (R) is the correct explanation of (A).

Both (A) and (R) are true but (R) is NOT the correct explanation of (A).

Chemistry · p-Block (I) (Grp. 13, 14)

JEE Main 2024 — 8 April, Shift 1 — Question 60

Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): The stability order of +1 oxidation state of Ga , In and Tl is $\mathrm{Ga}<\mathrm{In}<\mathrm{Tl}$ .

Reason (R): The inert pair effect stabilizes the lower oxidation state down the group.

In the light of the above statements, choose the correct answer from the options given below :

Option A:
Both (A) and (R) are true and (R) is the correct explanation of (A).
Correct
Option B:
Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
Option C:
(A) is true but (R) is false.
Option D:
(A) is false but (R) is true.

Answer: A

Step-by-step solution

Assertion A is True: In Group 13 elements (Ga, In and Tl), the stability of the $+1$ oxidation state increases down the group. This is because the tendency of the outermost $ns^2$ electron pair to participate in bonding decreases from Ga to Tl. Hence, the stability order is $\mathrm{Ga < In < Tl}$ .

Reason R is True: The inert pair effect refers to the reluctance of the $ns^2$ electron pair to take part in bond formation, which becomes more pronounced down the group due to poor shielding by intervening $d$ and $f$ electrons.

The inert pair effect stabilizes the lower oxidation state ( $+1$ ) in heavier Group 13 elements and therefore correctly explains Assertion A.

Answer key and solution verified before publishing.

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Exam: JEE Main 2024
Paper: 8 April, Shift 1
Subject: Chemistry
Chapter: p-Block (I) (Grp. 13, 14)
Topic: Introduction & Properties of Group 13: Boron Family