I have an exercise with the following text: Suppose you put both electrons in a helium atom into the n=2 state. What would the energy of the emitted electron be? I have attached the solution to the problem, but I am not sure I understand it. I understand the first part about the total initial energy. But I don't understand what follows. If the energy of each electron is E1 and one electron drops to a state below then shouldn't it only lose a portion of energy while leaving the other electrons energy unchanged? Maybe I am thinking too clasically and should think of it as a total quantum system. But it is just weird for me that the electron can gain energy through the other jumping down - how is this energy transferred? (maybe too classical again) - and most importantly, why are we not considering the fact that the energy jump will cause a photon to be emitted like in the hydrogen case?