(1) S > Se > Te > O
Oxygen is the second most electronegative element in comparison to fluorine. In group - 16 family (O, S, Se, Te), O-atom is smallest in size. So, electron density on O-atom is very high in group -16 During addition of a free electron to gaseous O-atom,
\(O(g) + e ^- \rightarrow O^- (g)\)
We have to supply a significant amount of energy (endothermic) to overcome the electrostatic repulsion between the approaching electron and O-atom of very high electron density. So, the net value of electron affinity (EA) or (negative) electron gain enthalpy \([\Delta _{eg}H\,or| \Delta _{eg}H|]\) of oxygen decreases to a higher extent in comparison to other elements of group -16 who have larger size and lower electronegativity.
So, the correct order of EA or \(|\Delta _{eg}H|\) of group −16 elements will be S > Se > Te > O
