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

Explanation

Alkaline earth metals have stable `ns^2` configuration & are reluctant to accept electrons. Thus, their electron affinity values are nearly zero. These are metallic by nature and highly electropositive also, that is, they as it is have a poor tendency to accept electrons. The negative anions of group-2 metals are not known.