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The electron gain enthalpy(in kJ/mol) of fluorine, chlorine, bromine and iodine respectively are:
Option: 1 -333,\: \: -349,\: \: -325\: \: and\: -296
Option: 2 -296,\: \: -325\: \:-333,\: \:and\: -349
Option: 3 -333,\: \: -325\: \:-349\: \:and\: -296
Option: 4 -349,\: \: -333,\: \: -325\: \: and\: -296

Answers (1)


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) + \DeltaegH


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.

Posted by

Kuldeep Maurya

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