Question

Define electron gain enthalpy? Why is the electron gain enthalpy of chlorine more negative than fluorine?

Answer 1

☆ Electron gain enthalpy

=> the electron gain enthalpy is the energy change that occurs for the process of adding an electron to a gaseous isolated atom to convert it into a negative ion .

electron gain enthalpy of chlorine is more negative than fluorine because,

=> electron gain enthalpy become less negative down a group . however, adding an electron of 2p - orbital leads to greater repulsion due to high electron density than adding an electron to the larger 3p orbital . hence chlorine has more negative electron gain enthalpy than fluorine.

Answer 2

Electron gain enthalpy is defined as the amount of energy released when an electron is added to an isolated gaseous atom.

The negative electron gain enthalpy of fluorine is less than that of chlorine. It is due to small size of fluorine atom. As a result, there are strong interelectronic repulsions in the relatively small 2p orbitals of fluorine and thus, the incoming electron does not experience much attraction.