Question

Electron affinity order of oxygen family??​

Answer 1

Answer:

O>S>Se>Te>Po

Basis: Decreasing EN.

Answer 2

Answer:

Here are the electron affinities of the 17th and 18th groups.

enter image description here

The general trend for electron affinity down the group is that it decreases because of the increase in atomic radius.The exception of Cl>F, I can understand is because fluorine has a high electron density and it is unfavourable to add more electrons as it would only increase the electron -electron repulsion.

The same reasoning can be applied to S>O. But oxygen's electron affinity is lesser than all the elements down group 17. Why is this so? And how is it so different from group 18 or why doesn't group 18 have F being less than the rest?.

I tried to apply the reasoning that the electron-electron repulsion in oxygen is so much that it is less favourable for O than any other element in group 17 to gain an electron. But in that case F is an even smaller atom hence with even more repulsion. So why are these two groups so different