Question

The absolute value of the electron gain enthalpy of halogens satisfies:

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• A. $Cl>Br>F>I$
• B. $F>Cl>Br>I$
• C. $I>Br>Cl>F$
• D. $Cl>F>Br>I$

Answer 1

The correct option is D $Cl>F>Br>I$

The magnitude of electron gain enthalpy of halogen atoms down the group shows abnormal behaviour. The $|\Delta H_{eg}|$ of $F$ is lower than that of $Cl$ due to its smaller size. The incoming electron experiences higher repulsive force due to valence electrons of $F$ than $Cl$. The correct order is $Cl>F>Br>I$
Option d is the correct answer.