## Electron Spin

Posts: 62
Joined: Wed Sep 30, 2020 9:33 pm

### Electron Spin

I know that two electrons can only exist in an orbital if they have an opposite spin. However, I'm still confused about how to determine which electron has a +1/2 or -1/2 spin. Does the first electron in the orbital typically have a +1/2 spin and the second a -1/2 spin?

Posts: 63
Joined: Wed Sep 30, 2020 10:07 pm
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### Re: Electron Spin

Yeah, the first electron is spin up (+1/2) and the second electron is spin down (-1/2). Also, when we draw Aufbau diagrams, the first arrow will be pointed up and the second down for each set of paired electrons because each set of paired electrons have electrons with opposite spins.

Emmeline Phu 1G
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Joined: Wed Sep 30, 2020 9:52 pm
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### Re: Electron Spin

Hi! The first electron in an orbital has an up spin (+1/2) and so does all of the first electrons in each orbital in a sub shell. The second electron in an orbital has a down spin; therefore, it is (-1/2). Due to the Pauli exclusion principle, two electrons in the same orbital have a paired spin in which one spin is up and the other is down. Hope this helps! :)

Praneetha Kakarla 3A
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### Re: Electron Spin

The convention is that the 1st electron spins up & the 2nd spins down, but in reality, it's actually arbitrary. I believe Prof. Lavelle mentioned in last Friday's lecture how what we classify as up & down in terms of electron spin is arbitrary.

Kathy_Li_1H
Posts: 55
Joined: Wed Sep 30, 2020 9:31 pm

### Re: Electron Spin

Hi! Typically, the first electron has a positive spin; however, this concept is arbitrary so technically you can have the first electron have any spin as long as the next electron has the opposite spin.

Tobie Jessup 2E
Posts: 54
Joined: Wed Sep 30, 2020 10:02 pm

### Re: Electron Spin

We say that the first electron spins up, but that value doesn't mean much since the positive and negative directions don't have meaning. I know that 2 electrons in the same sub shell do not spin the same direction.

Cassidy Cheng 1J
Posts: 56
Joined: Wed Sep 30, 2020 9:33 pm

### Re: Electron Spin

Typically, the first electron is +1/2 and the second is -1/2, but it's arbitrary, like the other commenters said. I think we're just accustomed to drawing them out like that, so that's why we typically make the first electron be +1/2.

Nan_Guan_1L
Posts: 59
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Electron Spin

we usually consider the first electron to spin up (+1/2) and the second electron to spin down (-1/2). but I think Dr. Lavelle mentioned in class that these are just math models that scientists employed to represent the opposite spin of electrons in the same sub shell and they don't really exist.