Which of the elements has the greatest electron affinity among the halogens.

Options

A. Cl
B. Br
C. I
D. F

Answer

A

Explanation

The electron affinity decreases from `Cl rarr Br rarr I`, i.e., on moving down the group. However, electron affinity of florine is unexpected low. It cannot be explained by any simple mechanism. It is probably due to small size of the atom. The addition of an extra electron produces high electron charge density in a relatively compect 2p subshell resulting in strong electron-electron repulsion. The repulsive forces between electrons imply low electron affinity So, the correct order of electron affinity for halogens is
`I lt Br lt F lt Cl.