Question

How does the following property vary on moving down group 17?

Electron affinity

Answer 1

1. Halogens have high electron affinity values.
2. Electron affinity is highest for chlorine, not fluorine.
3. On moving down the group, electron affinity generally decreases from chlorine to iodine.
4. Fluorine’s lower electron affinity than chlorine is due to its small size and high electron density repelling the added electron.
5. The trend follows: F < Cl > Br > I.

This occurs because as atomic size increases down the group, the attraction for the incoming electron decreases, releasing less energy on electron addition.