Question

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

• A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
• B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  
• C. Assertion is correct statement but reason is wrong statement.
• D. Assertion is wrong statement but reason is correct statement.

Answer 1

The correct option is A Assertion and reason both are correct statements and reason is correct explanation for assertion.

In case of isoelectronic species, effective nuclear charge increases with increase in atomic number $Z$ (with increase in protons). This results in decrease in size and hence, ionic radius of ${Al}^{3+}<{Na}^{+}$.