Why EA of fluorine is less than chlorine?

Answer 1

Generally electron affinity goes up as you go from left to right across the Periodic Table, and decreases as you go down a column. However, fluorine is an exception -- and the element with the highest electron affinity is chlorine (note that the most electronegative element is fluorine however).

The reason that the electron affinity is not as high as might otherwise be predicted for fluorine is that it is an extremely small atom, and so it's electron density is very high. Adding an additional electron is therefore not quite as favorable as for an element like chlorine where the electron density is slightly lower (due to electron-electron repulsion between the added electron and the other electrons in the electron cloud).

Note that there are a number of other exceptions to the general rule of electron affinity increasing towards the upper right corner -- see the Related Questions links to the left for an explanation of some of those other exceptions.

See also the Web Links to the left for more information about electron affinities and the fluorine-chlorine exception.

Answer 2

Because of large electron-electron repulsion among the lone pairs in F2 than that of Cl2.

OR

F-F bond is short as Fluorine atoms are extremely small. Thus it strengthens the repulsion between lone pair and weakens the bond.

Answer 3

well it appears to be , under experimental microscopes, that the bond energy for fluorine is less than Chlorine because the F-F bonds have electrons repulsions that appear to be causing this misleading fact. There are exceptions to every model.

Answer 4

It is the same reason that oxygen has less negative electron gain enthalpy than sulphur which is the succeeding element down a group.

When an electron is added to oxygen or fluorine (electron gain enthalpy) the added electron goes into the lower energy (n=2) level, where it suffers sufficient repulsion from the other electrons that are already present in the 2p sub-shell. However in chlorine or sulphur, the added electron goes into 3p sub-shell and therefore occupies a larger space, thus electron-electron repulsion is reduced and thus electron gain enthalpy is more -ve. (more energy is released)

Hope it helps

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Answer 5

The reason for Fluorine's low dissociation energy is due to a combination of factors. The simple explanation is that Fluorine is a halogen and halogens are by nature very electronegative, with Fluorine being the most electronegative. Their electronegativty can be attributed to its desire to have a fully filled valence shell [F]2s22p5 and therefore have an octet. Therefore any covalent/ionic bond associated with Fluorine will have most of its electon density situated near Fluorine. When Fluorine dissocaites the electron that was once shared will now transfer to Fluorine giving it an octet.

Answer 6

The atomic size of fluorine is very small. So addition of one more electron to the electrons already present in the fluorine atom will make it unstable due to repulsion between the electrons. Hence the electron affinity of fluorine is smaller than that of chlorine.

Answer 7

in fluorine the repulsion between lone pairs on the two atoms which weakens the bond.