## Spin Quantum Number

Doreen Liu 4D
Posts: 54
Joined: Wed Sep 11, 2019 12:17 am

### Spin Quantum Number

I know that the spin quantum (ms) describes the angular momentum of an electron, but I am confused on when to use that number +1/2 and -1/2 or is it only for drawing the arrows?

Parker Smith
Posts: 102
Joined: Thu Jul 25, 2019 12:15 am

### Re: Spin Quantum Number

the +1/2 and the -1/2 are used to signify the spin of the electron. So if you are only drawing the arrows, you probably don't need to use the ms numbers because the arrows signify spin direction already. It depends on what the problem asks of you.

Michelle Le 1J
Posts: 50
Joined: Fri Aug 09, 2019 12:16 am

### Re: Spin Quantum Number

The four quantum numbers altogether help to completely describe an electron in an atom and its spin state, thus you would use that number to specify the spin state of a certain electron.

KBELTRAMI_1E
Posts: 108
Joined: Sat Jul 20, 2019 12:17 am

### Re: Spin Quantum Number

Parker Smith wrote:the +1/2 and the -1/2 are used to signify the spin of the electron. So if you are only drawing the arrows, you probably don't need to use the ms numbers because the arrows signify spin direction already. It depends on what the problem asks of you.

how do you know which direction it goes though?

Posts: 116
Joined: Thu Jul 25, 2019 12:15 am

### Re: Spin Quantum Number

We generally say that the first electron is up and the second is down. We can only determine spin experimentally and therefore just need to know theoretically what the spin would be (based on what we know about electron repulsion).

Kassidy Ford 1I
Posts: 103
Joined: Sat Aug 17, 2019 12:16 am
Been upvoted: 1 time

### Re: Spin Quantum Number

It is also good to know that when electrons are paired, they have opposite spins. when electrons are unpaired but in the same orbital, they have parallel spins