Question
The electron gain enthalpy of fluorine has less negative value than that of chlorine while it is expected to be more. Explain.
Solution
The electronic configuration of F and Cl can be represented as:
Within a group, electron gain enthalpy becomes less negative down a group. However, adding an electron to the 2p orbital in fluorine leads to greater repulsion than adding an electron to the larger 3p orbital of chlorine. Hence chlorine has more negative electron gain enthalpy than that of fluorine.
