JEE Main 2022 · 27 Jun · Shift 1 · Chemistry Q65

ChemistrySingle correct+4 / -1Question 65 of 90

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

Assertion (A) : The ionic radii of $\mathrm{O^{2-}}$ and $\mathrm{Mg^{2+}}$ are same.

Reason (R) : Both $\mathrm{O^{2-}}$ and $\mathrm{Mg^{2+}}$ are isoelectronic species.

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).

(A) is true but (R) is false.

(A) is false but (R) is true.

Answer and worked solution

Official answer: D

Assertion is false: $\mathrm{O^{2-}}$ (140 pm) is far larger than $\mathrm{Mg^{2+}}$ (72 pm), since Mg has a higher nuclear charge.

Reason is true: both have 10 electrons.

(D)

Topics:Atomic and ionic radii

JEE Main 2022 · 27 Jun · Shift 1, Chemistry question 65