Q56 / 200 · NEET 2005 · Chemistry

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species?

  • A
    S $ < $ O $ < $ Cl $ < $ F
  • B
    $\mathrm{Cl} < $ F $ < $ S $ < $ O
  • C
    F $ < $ Cl $ < \mathrm{O} < \mathrm{S}$
  • Correct answer
    D
    $\mathrm{O} < \mathrm{S} < \mathrm{F} < \mathrm{Cl}$

Solution

The electron gain enthalpy of elements increases along a period towards right and decreases down the group. However, the $\mathrm{EA}$ of $\mathrm{Cl}$ is higher than that of $F$ and EA of $S$ is higher than that of $\mathrm{O}$ as $\mathrm{F}$ and $\mathrm{O}$ are very small in size. Thus, the correct order of EA is: $$ \mathrm{O} < \mathrm{S} < \mathrm{F} < \mathrm{Cl} $$ Caution Oxygen molecule has a less negative electron gain enthalpy than sulphur. This is on the grounds that Oxygen, because of its compressed nature encounter more repulsion between the electrons effectively present and the approaching electron.

Hence, the correct answer is option: 'D'.

Relevant Questions