Subset of: How can antibonding orbitals be more antibonding than bonding orbitals are bonding?
Stability of $\ce{H2^{-}}<\ce{H2^{+}}<\ce{H2}$
Stability of $\ce{N2^{-}}<\ce{N2^{+}}<\ce{N2}$
Source: Online lecture Etoosindia.
I am more concerned of $\ce{H2^{-}}<\ce{H2^{+}}$.
Does any satisfactory explanation exists (perhaps which can be generalized) for it? That is to add electron in anti-bonding molecular orbital more difficult than removing electron from bonding molecular orbital?
Observation indicates that First ionization energy of $\ce{H2}$ is greater than electron gain enthalpy (magnitude).
