Question

Assertion (A) $Na ^{+}$ and $Mg ^{2+}$ ions are isoelectronic but the ionic radius of $Na ^{+}$ is greater than that of $Mg ^{2+}$
Reason (R) The effective nuclear charge of $Na ^{+}$ ion is less than that of $Mg ^{2+}$ ion

• A. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• B. Both (A) and (R) are correct and (R) is correct explanation of (A)
• C. (A) is not correct but (R) is correct
• D. (A) is correct but (R) is not correct

Answer 1

Answer: (B)

$\because$ For isoelectronic species:

$r \propto \frac{1}{\text { ettective nuclear charge }}$

$\therefore $ Both $(A)$ and $(R)$ are correct and $(R)$ is the correct explanation of $(A)$.