The electron gain enthalpy values of $\mathrm{N},\mathrm{O},\mathrm{S}$ and $\mathrm{Cl}$ are

We know that electron gain enthalpy is the tendency to gain an electron.

We also know that as we move along the period it increases and in group as well. So the correct order is $\mathrm{N}<\mathrm{O}<\mathrm{S}<\mathrm{Cl}$