The electron gain enthalpy(in kJ/mol) of fluorine, chlorine, bromine and iodine respectively are:
Option: 1
Option: 2
Option: 3
Option: 4
Electron Gain Enthalpy or Electron Affinity -
Electron Affinity
Electron gain enthalpy is the energy change that occurs when an electron is added to a neutral gaseous atom to form a negative ion. It is also known as electron affinity.
A(g) + e →A-(g) + egH
Variation of Electron Affinity
The electron gain enthalpy becomes less negative in going from top to bottom in a group.
In moving from top to bottom in a group, both the atomic size and the nuclear charge increase. But the effect of the increase in atomic size is more prevalent than the nuclear charge.
Halogens have the most negative electron gain enthalpies. In moving down from chlorine to iodine, the electron gain enthalpies become less negative due to the increase in their atomic radii.
Chlorine has the most negative electron gain enthalpy value than fluorine. Because fluorine is very small in size due to which there is a very strong inter-electronic repulsion for the incoming electron, thus its electron gain enthalpy is less than chlorine.
The electron gain enthalpy values are given below:
Fluorine = -333kJ/mol
Chlorine = -349kJ/mol
Bromine = -325kJ/mol
Iodine = -296kJ/mlol
Therefore, Option(1) is correct.
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