There's something that doesn't make sense to me regarding these two rules. I was hoping someone could pat me on the head and tell me that everything was okay, and that both Slater's Rules and Hunds rule were actually complimentary and correct. So when beginning to explain Slater's Rules, electrons are grouped by principal quantum number (n), and by their spin (l). Except s and p share the same group. ie: [1s] [2s, 2p] [3s, 3p] [3d] [4s, 4p], [4d], [4f] When USING Slaters rules you get the levels of effective charge in constantly decending amounts from [1s] all the way down to [4s] However.... what doesn't make sense to me is Hunds Rule that seems to contradict this. Hunds rule says they DON'T accend by quantum number and spin, but electrons actually fill up like this: [1s] [2s] [2p] [3s] [3p] [4s] [3d] [4p].............. And that (carrying the sequence on) 4f orbitals don't fill up until AFTER the 6s orbitals. Would this necessarily suggest that electrons in the 6s orbital have less effective charge than electrons in the 4f orbital? And if so, why on earth does Slaters Rules state they must be in plain old accending quantum order? Confused. Can anyone fill me in on this?