Question

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

Answer 1

Hint: Fluorine and chlorine belongs to the same group halogens. The reason for electronegativity can be determined by the properties like atomic size, interelectronic repulsion.

Complete step by step answer:
First, we will see the electronic configuration of chlorine, and fluorine. Chlorine has atomic number 17 with the electronic configuration [Ne]3s$^{2}$3p$^{5}$, and fluorine has 9 atomic number with the electronic configuration [Xe]2s$^{2}$2p$^{5}$.
If we see the periodic table, chlorine is placed between the fluorine and bromine, whereas fluorine is placed at the upper position in the group 17 of the periodic table.
Fluorine is small in size; the strong interelectronic repulsions are present in the 2p orbitals.
We can say that due to strong interelectronic repulsions, it doesn’t accept the electron easily, whereas in case of chlorine interelectronic repulsions are less, so it attracts the incoming electron i.e. accepts the electrons to show further bonding.
We can conclude that the electron gain enthalpy depends upon size, interelectronic repulsions and acceptance of electrons in the orbitals.
Therefore, from the above mentioned reasons we can say that the electron gain enthalpy of chlorine is more negative than the fluorine.

Note: Don’t get confused between the chlorine and fluorine. These both represent the halogen groups, but their difference can be characterized by the physical and chemical properties shown by the elements in the periodic table like ionization enthalpy, size, ionic radius, oxidation states, and many more.