question_answer 57)

  Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is: (a) \[F>Cl>Br>I\]              (b) \[F<Cl<Br<I\]              (c) \[F<Cl>Br>I\]               (d) \[F<Cl<Br>I\]

Answer:

  (c) Chlorine has higher electron gain enthalpy than fluorine. This is due to small size of fluorine atom, i.e., the electron density is high which resists the addition of an electron \[\left( \text{F  Cl} \right)\]. In general, electron gain enthalpy decreases as atomic size increases. Thus, \[Cl\text{ }>\text{ }Br\text{ }>\text{ }I\]