Question

Out of the following which has more negative electron gain enthalpy. Justify your answer. F Or Cl

Answer 1

Answer:

Cl has a higher electron affinity than F because electronic repulsions are greater in the smaller Fatom.

Explanation:

Electron affinity is the enthalpy change when 1 mol of gaseous atoms each gain an electron to form 1 mol of gaseous ions.

It is the enthalpy change for:

X(g)+e−→X−(g)

For fluorine the electron affinity = -328 kJ⋅mol-1

For chlorine the electron affinity= -349 kJ.mol-1

So, we can see that the value for chlorine is larger and negative compared with fluorine.

Both Cl and F are quite happy to accept an electron to complete their octet and get to a lower energy level.

But F is a smaller atom, so the electrons are crowded together more closely.

The electron repulsions are greater in the F atom, so there is not as much energy available to be released when the electron is added.

Fluorine, since it's such a small atom, has a very high electron density, which means that the repulsion the incoming electron feels will diminish the attraction coming from the nucleus and thus reduce its electron affinity.

you can also refer to above diagram....

hope this helps...

Answer 2

Answer:

Due to its small size, the electron–electron repulsions in the relatively compact 2p-sub-shell are comparatively large, and hence, the incoming electron is not accepted with the same ease as is the case with larger Cl atom. Consequently, electron gain enthalpy of Cl is more negative than that of F.