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

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

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

(B) Both (A) and (R) are true but (R) is not the correct explanation of (A)

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

JEE Main · 2022 · 27 Jun 2022 · Shift 1 · Classification of Elements and Periodicity

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

O^{2 -}

and

Mg^{2 +}

are same.

Reason (R) : Both

O^{2 -}

and

Mg^{2 +}

are isoelectronic species

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

Answer: (D)

Both

O^{2 -}

and

Mg^{2 +}

are isoelectronic with 10 electrons each (electronic configuration:

1 s^{2} 2 s^{2} 2 p^{6}

), so the reason is true. However, the ionic radius of

O^{2 -}

is larger than that of

Mg^{2 +}

because

Mg^{2 +}

has a higher nuclear charge (12 protons vs 8 protons), which pulls the electrons closer. Therefore, the assertion is false but the reason is true.

JEE Main · 2022 · 27 Jun 2022 · Shift 1 · Single correct option