Question

Assertion: $N{a}^{+}$ and $A{l}^{3+}$ are isoelectronic but the magnitude of ionic radius of $A{l}^{3+}$ is less than that of $N{a}^{+}$.
Reason: The magnitude of effective nuclear charge on the outer shell electrons in $A{l}^{3+}$ is greater than that in $N{a}^{+}$

• A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
• B. Both Assertion and Reason are true and Reason is not the correct explanation of Assertion.
• C. Assertion is true but Reason is false
• D. Both Assertion and Reason are false

Answer 1

The correct option is A Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Isoelectronic species will have same number of electrons.
Amongst isoelectronic species, ionic radii decrease with increase in effective nuclear charge.
Since, atomic number of $Al$ is higher than $Na$, $A{l}^{3+}$ will have the more effective nulcear charge than $N{a}^{+}$ over the same number of electrons. Thus, result in smaller size of $A{l}^{3+}$ compared to $N{a}^{+}$

Hence, option (a) is correct.