Atoms A and B each have a single valence electron. The ionization energy of A is 4 eV and that of B is 6 eV. The energy of the AB bonding MO is sigma AB= -9 eV and the AB anti bonding MO is sigma star AB = -2 eV. Calculate the energy change, in eV, for the ion combination process A (g) + B-(g)-> AB-(g)