Import Question JSON

$\text{HINT: 3rd-period elements are having higher electron affinity than 2nd period elements.}$ $\text{Explanation:}$ $\text{The electron gain enthalpy is seen to decrease on moving down a group and increases from moving left to right in a period. Due to the smaller size of the members of III period compared to the corresponding members of second period, they have higher electron gain enthalpy.}$ $\text{Thus, the electron gain enthalpy of Cl and F (17 group) is higher as compared to O and S (16 group).}$ $\text{Cl has higher electron gain enthalpy as compared to F, this is because due to the small size of F atom, the incoming electron experiences a greater force of repulsion.}$ $\text{Similarly, the electron gain enthalpy of S is higher as compared to O due to its small size.}$ $\text{Therefore, the correct order of electron gain enthalpy of given elements is :}$ $\text{O} < \text{S} < \text{F} < \text{Cl}$ $\text{Note: Electron affinity and electron gain enthalpy are related concepts:}$ $\text{- Electron affinity is the magnitude of energy released when an electron is added}$ $\text{- Higher electron gain enthalpy (more negative value) corresponds to higher electron affinity}$ $\text{- The order O} < \text{S} < \text{F} < \text{Cl represents increasing electron affinity}$ $\text{Key factors affecting the order:}$ $\text{1. Group 17 elements (F, Cl) have higher electron affinity than Group 16 elements (O, S)}$ $\text{2. Within Group 17: Cl} > \text{F due to electron repulsion in small F atom}$ $\text{3. Within Group 16: S} > \text{O due to larger size of S reducing electron repulsion}$