Question

Why negative value of electron gain enthalpy than fluorine?

Answer 1

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Electron gain enthalpy is the energy change when an electron is added to an isolated gaseous atom.

With this definition, consider fluorine. It is the smallest element (with respect to atomic radius) in its period.

It also has 7 electrons in its outermost shell, the L (2nd) shell.

When you add an electron, there is extra repulsion between these electrons.In the case of chlorine, it also is the smallest in its period, and has 7 electrons in its outermost shell, the M (3rd) shell in this case.

Adding another electron to chlorine is relatively easier, as there is more space, and also the empty d-orbital can accomodate this electron.

For fluorine, imagine adding a person to a car with 7 persons.For chlorine, imagine adding a person to a bus with 7 persons.

This inter-electronic repulsion is what makes the electron gain enthalpy of chlorine the highest, greater than that of fluorine

Answer 2

Explanation:

ELECTRON GAIN ENTHALPY OR ELECTRON AFFINITY :

AMOUNT OF ENERGY REALESD WHEN AN ISOLATED GASEOUS ATOM ACCEPTS AN ELECTRON TO BECOME GASEOUS NEGATIVE ION.

CHLORINE HAS LOWER ELECTRON AFFINITY THAN FLUORINE BECAUSE FLUORINE HAS HIGHER ELECTRON DENSITY SO ONE ELECTRON ADDED TO ITS SHELL SO MORE ENERGY WILL BE REALESD .