posted by Sue .
My question is, Hund's rule states that the electrons pair up only after each orbital in a sublevel is occupied by ______. I think its one electron, but the more I read I'm confused because it says about an electron with a spin cycle.
You are correct. Hund's rule states that an electron pairs when there is no other option available; i.e., when there is no orbital available with NO electron in it. Then it MUST pair with an electron that is already there. When that electron pairs, it does so with an electron of the opposite spin in one of the orbitals with an electron there. I hope this clears up any confusion you have.