Question

Electron gain enthalpy of oxygen is less than that of sulphur. Why?

Answer 1

The negative electron gain enthalpy is more in sulphur than in oxygen because both of are them in 16th group in which the oxygen is first element which has the minimum size and sulphur has larger size due addition of a new shell.

So, due to smaller size the inter-electronic repulsion in compact 2p-orbitals ofoxygen is much more than the repulsion in 3p-orbitals of sulphur hence, the incoming new electron feels less attraction in oxygen and more attraction in sulphur due to which the addition becomes easy and so electron gain enthalpy becomes more negative in sulphur.