Electron gain enthalpy increases across the period and decreases down the group. Which of the following order of electron gain enthalpy is correct ?
| A. |
F < Cl < Br < I |
| B. |
F < Cl > Br > I |
 |
| C. |
I > Br > F < Cl |
| D. |
I < Cl < Br > F |
As we knwo electron gain enthalpy decreases down the group. Hence, the order should be F > Cl > Br > I but correct order of electorn gain enthalpy is F < Cl > Br > I due to small size of Fatom. It requires high energy to become `F^(theta)` by accepting electrons.