Question

Assertion (A): Fluorine has smaller negative electron gain enthalpy than chlorine.
Reason (R): The electron-electron repulsion is higher in chlorine than in fluorine.

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

Hint:

Smaller atoms like fluorine have more electron-electron repulsion, leading to less negative electron gain enthalpy compared to larger atoms like chlorine.

Answer 1

The Correct Option is C

Electron gain enthalpy is the energy change when an atom gains an electron. Fluorine (\(-328 \, \text{kJ mol}^{-1}\)) has a less negative value than chlorine (\(-349 \, \text{kJ mol}^{-1}\)), so (A) is correct: fluorine has a smaller negative electron gain enthalpy than chlorine. However, (R) is incorrect because fluorine, being smaller, has more electron-electron repulsion in its 2p orbitals than chlorine, which has larger 3p orbitals. The higher repulsion in fluorine makes it harder to add an electron, not chlorine. Thus, (A) is correct, but (R) is incorrect. Thus, the correct answer is option 3.