Electron affinities, Ea, E1 and A1 are reported for the 12 primary X, A–K (27 spin) states of O2(−): KeqT3/2 = (SanQan)(2πmek/h2)3/2exp(Ea/RT); k1 = A1T−1/2exp(−E1/RT). These are obtained from pulsed discharge electron capture detector data by rigorously including literature values and uncertainties in a global non-linear least-squares adjustment. Simple molecular orbital theory predicts 27 bonding and 27 anti-bonding low-lying spin states. For the first time, the positive Ea for the 27 bonding states are reported. The partition function ratios of the negative ion and neutral (SanQan), the A1(X–E) and the spin separations are from fundamental constants. The Ea (in eV) are as follows (with the spin states in brackets): [1.050, 1.070]; [0.915, 0.935]; [0.698, 0.718, 0.746, 0.782]; [0.734, 0.754]; [0.559, 0.587]; 0.518; [0.430, 0.450]; 0.380; 0.354; [0.286, 0.298, 0.318, 0.346]; [0.232, 0.252]; [0.172, 0.184, 0.204, 0.232]. The activation energies (in eV) are as follows: E1(X–C) 1.0; E1(D,E) 1.0, 0.8, 0.6; E1(F–K) 0.12–0.08. The Ea and E1 are used to calculate bonding Herschbach ionic Morse–Person empirical curves.