Question

Why do halogens have very high values of electron affinity?

Answer 1

1. Halogens have 7 electrons in their outer shell, needing only one more electron to complete their stable noble gas configuration.
2. Because of this, halogens strongly attract an extra electron to attain stability.
3. The high effective nuclear charge in halogen atoms pulls the incoming electron strongly.
4. When an electron is added, a large amount of energy is released, resulting in very high (maximum negative) electron affinity values.
5. The electron affinity decreases down the group because atomic size increases; thus, the attraction for the added electron reduces.
6. Fluorine’s electron affinity is slightly less negative than chlorine’s due to its very small size causing high electron density, which repels the added electron a bit.