Spin Magnetic Quantum Number

[KMcFarland_2L]

The spin magnetic quantum number can either be +1/2 or -1/2 based on if the electron is spun up or down, but how do you determine which direction it is spun?

[Brianne Conway 1D]

I don't think we need to know how to actually determine it; I'm pretty sure that has to do with Schrodinger's equation. We just need to know which number signifies which spin.

[Margia Adriano 2A]

Hi! I don't think it is too important or necessary for us to know whether an electron is spin up or down, just that you know the ms=+1/2 is spin up and ms=-1/2 is spin down and that a filled orbital cannot have two of the same. Hope this helps!

[Katie Phan 1K]

Yes, I don't think you need to know how to determine it, just need to know the quantum numbers.

[Linette Choi 3L]

I also don't believe you need to know how to calculate it. However, you can determine the spin by the number of electrons in the atom. For instance, using Hund's rule, for an element like Carbon which is 1s2 2s2 2p2, the two S orbitals are filled with arrows, however with the remainder of the arrows, only two of the P orbital are filled with positive arrows. This would indicate that there is a positive +1/2 spin in the P orbital.

Ex: ↑ ↓ ↑ ↓ ↑ ↑
1s2 2s2 2p2

[Samudrala_Vaishnavi 3A]

For the spin magnetic quantum number, the +1/2 indicates up and the -1/2 indicates down. We were never taught how to actually calculate the spin, but there is some conceptual knowledge about how it was discovered in the first place which could guide your understanding. The Stern and Gerlach experiment that we learned about tells us why there are only two different spin numbers and how this correlates to unpaired electrons. Just some things to note, remember that if you are doing an electron configuration that you note the electrons per orbital as spin up first and then spin down for the s orbital and for the p, d, and f orbitals use spin up to fill all the orbitals and THEN spin down to pair them once you have filled all the orbitals of the subshell.

[Nicoli Peiris 1B]

I don’t think we have to know that. Just know +1/2 spin up and -1/2 is spin down!