Question

For the element $O$ or $F$, the electron gain enthalpy is less negative than that of the succeeding element. Electron gain enthalpy becomes less negative as we go down a group.

• A. If both assertion and reason are true and reason is the correct explanation of assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false.

Answer 1

Answer: (B)

If both assertion and reason are true but reason is not the correct explanation of assertion.

Answer 2

Generally, electron gain enthalpy becomes less negative (decreases) as we go down the group because size of the atom increases and the added electron will be farther from the nucleus. But in case of $O$ or $F$, the added electron goes to the smaller quantum level i.e., $n = 2$ and suffers significant repulsion from other electrons present in this level.