Assertion (A): The electron gain enthalpy of fluorine is less negative than that of chlorine. Reason (R): The small $2 p$ subshell of fluorine causes strong inter-electronic repulsion in the incoming electron.

ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is not the correct explanation of A
CA is true but R is false
DA is false but R is true

Answer: A

Both are true. In F the

2 p

subshell is very compact, so the added electron is strongly repelled, reducing the energy released. This is the accepted explanation for the Cl > F anomaly.

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Assertion (A): The electron gain enthalpy of fluorine is less negative than that of chlorine. Reason (R): The small 2p subshell of fluorine causes strong inter-electronic repulsion in the incoming electron.

Answer: A

More questions on Trends in halogens

Assertion (A): The electron gain enthalpy of fluorine is less negative than that of chlorine. Reason (R): The small $2 p$ subshell of fluorine causes strong inter-electronic repulsion in the incoming electron.