Question

What is the order of first electron affinity of group 16 family of periodic table?

Answer 1

Explanation:

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 16. Why is this so? And how is it so different from group 17 or why doesn't group 17 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 16 to gain an electron. But in that case F is an even smaller atom hence with even more repulsion.

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