Concept: Electron affinity is the energy released when an electron is added to a neutral gaseous atom to form a negative ion.
Explanation:1. All the given elements (F, Cl, Br, I) are halogens, belonging to Group 17.
2. Generally, electron affinity decreases down a group due to increasing atomic size and weaker attraction for the incoming electron. So, the expected order would be F > Cl > Br > I.
3. However, there is an anomaly: Chlorine (Cl) has a higher electron affinity than Fluorine (F).
4. This is because Fluorine has a very small atomic size, leading to high electron density in its
2p subshell. When an incoming electron approaches, it experiences significant interelectronic repulsion from the existing electrons.
5. Chlorine, being larger, has a lower electron density in its
3p subshell, resulting in less interelectronic repulsion for the incoming electron. This allows chlorine to accommodate the extra electron more readily and release more energy.
6. Therefore, the actual order of electron affinity for halogens is Cl > F > Br > I. Among the given options, Chlorine has the maximum electron affinity.
Answer: C. Cl
