In Reif's thermo book, one can read "Consider a substance which contains n magnetics atoms per unit volumes and which is placed in an external magnetic hield B. Assume that each atom has spin 1/2 (corresponding to one unpaired electron) and an intrinsic magnetic moment of [itex]\mu[/itex]." He makes it sound like it's possible to have more than one unpaired electron. Is this so? I interpret "unpaired" as "there is one electron in a state r and spin up (resp. down) such that there are no electrons in state r with spin down (resp. up). But as soon as you add one more electrons, it will get in state r with spin down (resp. up) so there are no more unpaired electrons. Hence it's impossible to have more than 1 unpaired. Is this how it work?
I'm not sure if I understand you completely but... look up Hund's rules. An atom can have more than one unpaired electron. They're in different angular momentum states though.
Surely if you've ever studied chemistry you might know that "unpaired electrons" occur when writing the electron configurations for various atoms. For instance, the Carbon atom has 2 unpaired electrons, N has 3, etc. Daniel.
What is an unpaired electron then? I've said what I remember from chemistry. You fill up the states two by two since an up and a down can occupy the same state. If there is an even number of electrons, there there is no unpaired electrons; if the number is odd there is one.
Nope, Hund rules make it that the Carbon atom which had 6 electrons altogether have the configuration 1s2 2s2 2p2 , but the 2 electrons in the "p" orbital are uncoupled (i.e. in different total angular momentul states), meaning that the spins are not antiparallel in the same orbital (p_{x}), but are alligned & parallel in the 2 orbitals:2p_{x} & 2p_{y}, rendering the total spin 1, instead of 0. Daniel.