Question

The electron affinity of fluorine is unexpectedly lower than that of chlorine. Comment on the statement and explain.

Answer 1

1. Fluorine is the most electronegative element and is expected to have the highest electron affinity.
2. However, its electron affinity is lower than chlorine's, which is unexpected.
3. The main reason is fluorine's very small atomic size.
4. This small size results in high electron density on fluorine's atom.
5. The high electron density causes strong electron-electron repulsion when an extra electron is added.
6. This repulsion makes it harder for fluorine to accept an electron smoothly.
7. Consequently, less energy is released when fluorine gains an electron compared to chlorine.
8. Chlorine, being larger, has less electron repulsion and thus a higher electron affinity.

Hence, fluorine’s lower electron affinity compared to chlorine is due to its small size and strong repulsion effects preventing easy acceptance of an electron.