Which will have greater electron affinity Oxygen or Fluorine ?

Explanation

`O to 2,6" "` Nuclear charge = 8 units
`F to 2, 7" "`Nuclear charge = 9 units
Increase in nuclear charge increases the effective force on the valence electron and hence the incoming electron can be held strongly and hence oxygen will have less electron affinity or fluorine will have greater electron affinity.
Thus we infer more is the nuclear charge, more is the hold of nuclear on incoming electron and hence electron affinity will be more.
Smaller the size greater is the nuclear charge and hence the electron affinity is relatively high.