## 4th quantum number question [ENDORSED]

Miriam Sheetz 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:25 am

### 4th quantum number question

I'm confused about the 4th quantum number and the significance of it? What does it mean for an electron to be spin up or spin down? How do you figure out if an atom is +1/2 or -1/2?

Nancy Hu - 4E
Posts: 30
Joined: Fri Sep 28, 2018 12:28 am

### Re: 4th quantum number question

So the 4th quantum number describes the spin of an electron. If the electron is spinning up, it has a value of +1/2. If the electron is spinning down, it has a value of -1/2. It is just used to describe the orientation of an electron in an orbital.

Jonathan Pai 2I
Posts: 121
Joined: Fri Sep 28, 2018 12:27 am

### Re: 4th quantum number question  [ENDORSED]

You do not need to figure out which spin it is, you just need to know there are two spins. So when it is asking about electrons, if you know n, l, and ml- there are two electrons, one with up spin and one with down spin.

Ex) electron 1-(3,2,-2, +.5), electron 2-(3,2,-2,-.5)

Manya Kidambi 3I
Posts: 31
Joined: Fri Sep 28, 2018 12:24 am

### Re: 4th quantum number question

+1/2 means an electron is spinning up, while -1/2 means it is spinning down. These are the only two values that the fourth quantum number can be.
An example:
Electron configuration 2p3. If you draw the orbital diagram, you have one arrow up and one down in the first electron pair, and one arrow up in the second.
Since it is up, the spin would be +1/2.