What is the correct order of electron gain enthalpy of Cl, F, Te, Po

We need to determine the correct order of electron gain enthalpy (in terms of magnitude, more negative = more exothermic = higher tendency to gain electron) for Cl, F, Te, and Po.

Among halogens, chlorine has the most negative electron gain enthalpy (not fluorine). This is because fluorine is very small and has high electron-electron repulsion in its compact 2p orbitals, making it slightly less favorable to add an electron compared to chlorine.

So: $$Cl > F$$ (in terms of magnitude of electron gain enthalpy)

Te and Po belong to Group 16. As we go down the group, the electron gain enthalpy generally decreases in magnitude due to increasing atomic size and shielding effects.

So: $$Te > Po$$

Halogens (Group 17) generally have more negative electron gain enthalpies than chalcogens (Group 16) of similar periods because halogens need just one electron to complete their octet.

So: $$Cl > F > Te > Po$$

Hence, the correct answer is Option B.