Which of the following species has the highest electron affinity?

Options

A. `F^(-)`
B. O
C. `O^(-)`
D. `Na^(+)`

Answer

B

Explanation

Electron affinity is the amount of energy released. Now energy is released when O or `Na^(+)` accepts an electron. But energy has to be supplied when an electron adds to `F^(-)` or `O^(-)`
`O(g)+e^(-) to O^(-) (g)+141 k J`
`Na^(+) (g)+e^(-) to Na(g)+496 kJ`
(I.E. of Na=+496 kJ `mol^(-1)`)
thus, more energy is released when `Na^(+)` accepts one electron
Thus option (D) is correct.