Question

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

• A. $F<Cl<O<S$
• B. $S<O<Cl<F$
• C. $O<S<F<Cl$
• D. $Cl<F<S<O$

Answer 1

Answer: (C)

$O<S<F<Cl$

The correct order of electron gain enthalpy (with negative sign) of given atomic species is $O<S<F<Cl$.

In a period, on moving from left to right, electron affinity increases due to increase in the effective nuclear charge and decrease in size.

In a group on moving from top to bottom, the electron affinity decreases due to decrease in the effective nuclear charge and increase in size. But there is an exception for $F$ and $O$ due to its small size.