MHT CET Chemistry Question (2026) — Solution

Step-by-step solution

Electron gain enthalpy is the enthalpy change when an electron is added to a neutral gaseous atom. Halogens such as Chlorine, Bromine, and Iodine have a strong tendency to accept an electron to achieve a stable noble gas configuration, resulting in highly negative electron gain enthalpies. Noble gases like Xenon have a completely filled and stable valence shell (ns^2 np^6). Adding an electron requires energy to place it in a higher energy principal quantum shell, overcoming interelectronic repulsions. Thus, Xenon has a positive electron gain enthalpy. Answer: Xenon