Hi all, I will be most grateful if someone could help me with this: 1) It can be shown that for two electrons the singlet energy is lower then the triplet energy. 2) According to Hund’s rule the ground spin state is symmetric. Why (1) is not correct for atoms where Hund’s rule can be used? Maybe the proof of (1) is wrong for more then two electrons but I can’t figure why. With thanks, Alex.