JEE Main 202227 JuneMorning Shift

JEE Main 2022 · 27 June · Morning Shift · Chemistry · Classification of Elements and Periodicity in Properties

Given below are two statements : one is labelled as Assertion and...

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

Assertion: The ionic radii of ${O}^{2 -}$ and ${Mg}^{2 +}$ are same.

Reason: 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.

Options

ABoth Assertion and Reason are true and Reason is the correct explanation of Assertion.
BBoth Assertion and Reason are true but Reason is not the correct explanation of Assertion.
CAssertion is true but Reason is false.
DAssertion is false but Reason is true.

D. Assertion is false but Reason is true.

Both ${Mg}^{2 +}$ and ${O}^{- 2}$ have $10$ electrons each and they are isoelectronic species.

But the size of ${O}^{- 2}$ is greater than ${Mg}^{2 +}$ as $size ∝ \dfrac{1}{\dfrac{z}{e}}$

$\dfrac{z}{e}of{Mg}^{2 +} = \dfrac{12}{10} = 1 . 2$

$\dfrac{z}{e}of{O}^{- 2} = \dfrac{8}{10} = 0 . 8$

$\dfrac{z}{e} = \dfrac{Numberofprotons}{Numberofelectrons}$