Question

Noble gases have positive electron gain enthalpy.Explain

Answer 1

Noble gases already have a very stable fully filled electronic configuration. Addition of another electron to a neutral inert gas atom would lead to high electronic repulsion and it would also destroy the already stable electronic configuration,which is highly unfavorable.
So, addition of an electron to the neutral atom requires a large amount of energy. As a result, the EGE of noble gases is positive.