Physics 2000 Science Trek Elements as Atoms

Quantum Numbers and Spin

Well, three quantum numbers down, one to go. You haven't mentioned anything about spin yet...

How perceptive of you. The fourth quantum number, s, does indeed pertain to an electron's spin.

I know that each electron has either "spin up" or "spin down"...

Yes, and, correspondingly, s only has two possible values. For good reasons that I shall not explain here, s= +1/2 means "spin up" and s= -1/2 means "spin down."

So that's it; those four quantum numbers completely describe an electron. I see how this fits in with Bob's visual picture of a "quantum state":

n=3, l=2, m=0
s= -1/2

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