If it's true in two cases, it's true in all (in this case)Originally posted by salsero
Suppose there are n electrons with angular momentum quantum numbers L1, L2, L3, ..., Ln. The total angular momentum L of the atom can be any number between the minimum and the maximum of all non-negative combinations +/- L1 +/- L2 +/- L3 ... +/- Ln (in steps of 1). Same about combinations of the spin (the spin quantum numbers of the single electrons are always 1/2) to the total spin S of the atom.
Hund's rule says that the lowest-energy state among all the possible states is the state which has the greatest S and the greatest L (for that S).