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Question: Answered & Verified by Expert
Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is
ChemistryClassification of Elements and Periodicity in Properties
Options:
  • A
    (a) $\mathrm{F}>\mathrm{Cl}>\mathrm{Br}>\mathrm{I}$
  • B
    (b) $\mathrm{F} < \mathrm{Cl} < \mathrm{Br} < \mathrm{I}$
  • C
    (c) $\mathrm{F} < \mathrm{Cl}>\mathrm{Br}>\mathrm{I}$
  • D
    (d) $\mathrm{F} < \mathrm{Cl} < \mathrm{Br} < \mathrm{I}$
Solution:
1249 Upvotes Verified Answer
The correct answer is:
(c) $\mathrm{F} < \mathrm{Cl}>\mathrm{Br}>\mathrm{I}$
As we move in a group from $\mathrm{Cl}$ to $\mathrm{I}$, the electron gain enthalpy (i.e., energy released in electron gain) become less and less negative due to corresponding increase in the atomic size.
However, the electron gain enthalpy of $F$ is less negative than that of $\mathrm{Cl}$ due to its small size. Thus, the negative electron gain enthalpy among halogens follows the order:
$\mathrm{F} < \mathrm{Cl}>\mathrm{Br}>\mathrm{I}$

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