Question

all the exceptions of electron gain enthalpy

Answer 1

In the case of Chlorine and Fluorine, Chlorine has a higher negative electron gain enthalpy value.
This is due to its small size. As a result of its small size, the electron-electron repulsion in the relatively compact to 2p subshell are comparatively large. Hence the incoming electron is not accepted with the same ease as is the case with chlorine.

In between Sulphur and Oxygen, Sulphur has a higher negative value than oxygen

The Electron Gain Enthalpy of Noble Gases is Positive

The atoms of these elements have completely filled subshell. As a result, there is no room in their valence orbitals and the additional electron has to be placed in an orbital of next higher shell. As a result, energy has to be supplied to add on additional electrons.
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Answer 2

Answer:

Exception in Electron Gain Enthalpy:

In the case of Chlorine and Fluorine, Chlorine has a higher negative electron gain enthalpy value. In between Sulphur and Oxygen, Sulphur has a higher negative value than oxygen.