Question

Which in each pair of elements has a more electron gain enthalpy? Explain.
(a) $N$ or $O$ (b) $F$ or $Cl$

Answer 1

$\left(a\right)$ Electron gain enthalpy depends on the size of an atom. Smaller the size, more negative would be the electron gain enthalpy. $F$ is a smaller size than $O$, thus electron gain enthalpy of $F$ is more negative than $O$.

$\left(b\right)$ $Cl$ is larger in size as compared to $F$, still electron gain enthalpy of $Cl$ is more negative than $F$, this is due to the fact that $F$ is very small in size due to which interelectronic repulsion takes place and the incoming electron does not feel so much attraction.