## Magnetic Spin Quantum Number

Ramneet Sandhu 3D
Posts: 50
Joined: Fri Aug 30, 2019 12:16 am

### Magnetic Spin Quantum Number

I'm confused on how to determine the magnetic spin quantum. I know it can be -1/2 or 1/2, but how do you determine which one it is?

Karina Kong 2H
Posts: 98
Joined: Thu Jul 25, 2019 12:16 am

### Re: Magnetic Spin Quantum Number

If the last electron that enters is spin up then it is +1/2. If the last electron that enters is spin down then it is -1/2.

805307623
Posts: 99
Joined: Fri Aug 09, 2019 12:17 am

### Re: Magnetic Spin Quantum Number

When filling an orbital you must fill all orbitals possible with one electron spin(spin up) before assigning the opposite spin(spin down). If the last electron that is filled into the orbital is spin up then the ms quantum # is + 1/2, but if the last electron is spin down then the ms quantum # is -1/2.

Daniel Chen 2L
Posts: 101
Joined: Fri Aug 30, 2019 12:15 am

### Re: Magnetic Spin Quantum Number

So for example, in the p-orbital, the first 3 electrons are up spins and the last 3 are down spins. So the first 3 are +1/2 since they are up spins and the last 3 are -1/2 since they are down spins.