Why the electron gain enthalpy values of alkaline earth metals are lower (i.e. less negative) or positive?

Why the electron gain enthalpy values of alkaline earth metals are lower or positive?

Comment on electron gain enthalpy of alkaline earth metals?

The ionisation enthalpy of alkaline earth metals is

The ionisation enthalpy of alkaline earth metals is

The calculated electron gain enthaly values for alkaline earth metals and noble gases are positive . How can you explain this ?

Why are electron-gain enthalpy of Be and N positive?

Why electron gain enthalpies of noble gases are positive ?

Why is the electron gain enthalpy of O or F less than that of S or Cl?