Hello, I'd like to ask a question about the electron binding energies of oxygen atom. As is known, when an oxygen atom gains one additional electron to form an anion with charge -1 it gives some 1.4ev, while it gives nearly 7.8ev if two additional electrons are bound to it. Considering that the second electron should feel a strong repulsion as it gets closer to the negatively charged anion, this seems remarkable. The only possibility to resolve this seems to take into account additonal energies. But what are they? And what are their magnitudes?