Question

Given below are two statements:
Statement (I): The radius of isoelectronic species increases in the order: \[ \text{Mg}^{2+} < \text{Na}^{+} < \text{F}^{-} < \text{O}^{2-} \] Statement (II): The magnitude of electron gain enthalpy of halogens decreases in the order: \[ \text{Cl} > \text{F} > \text{Br} > \text{I} \] In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct.
• B. Statement I is incorrect but Statement II is correct.
• C. Statement I is correct but Statement II is incorrect.
• D. Both Statement I and Statement II are incorrect.

Hint:

For isoelectronic species, the size decreases as the nuclear charge increases. Electron gain enthalpy becomes more negative as the atomic size increases.

Answer 1

The Correct Option is C

- Statement I: Correct. The radius of isoelectronic species decreases with increasing nuclear charge, as seen in the order \( \text{Mg}^{2+} < \text{Na}^{+} < \text{F}^{-} < \text{O}^{2-} \).
- Statement II: Incorrect. The electron gain enthalpy generally increases as we move down the halogen group, i.e., \( \text{I} > \text{Br} > \text{Cl} > \text{F} \), due to increased atomic size and shielding. 

Thus, Statement I is correct, but Statement II is incorrect.