NEET Chemistry Question (2026) — Solution

Step-by-step solution

The electron gain enthalpy generally becomes less negative as we move down a group due to the increase in atomic size. However, fluorine has a less negative electron gain enthalpy than chlorine. This is because fluorine has a very small atomic size, leading to strong interelectronic repulsions in the compact 2p subshell. As a result, the incoming electron experiences less attraction from the nucleus compared to chlorine. The values of electron gain enthalpy for halogens are approximately: Cl = -349 kJ/mol F = -328 kJ/mol Br = -325 kJ/mol I = -295 kJ/mol Considering the magnitude of electron gain enthalpy, the correct trend is Cl > F > Br > I . Answer: Cl > F > Br > I