Hi, I just completed an assignment modelling an atom with one electron. The model was very simple, assuming that only coulombs law applied, then solving for standing wave solutions to the Schrodinger equation to find ionization energies. I was astounded how accurate it was. i thought it would be maybe +/- 5% but instead it was correct within 0.5% for the first 10 atoms. It gave me a bit of an ego boost which is probably why im asking this. I noticed that for more than one electron the model failed spectacularly. Which got me wondering whats the next step? My guess is its the Pauli Exclusion Principle but how is it applied?