## Electron Spin

Diwana Lucero 3K
Posts: 26
Joined: Fri Jul 15, 2016 3:00 am

### Electron Spin

Can someone explain how to figure out if the arrows point up or down for an electron's spin state?

Kendall_Chaffin_3C
Posts: 25
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Electron Spin

If the electron spin is +1/2 the arrow points up and if the election spin is -1/2 the arrow points down.

Jonathan Sarquiz 3F
Posts: 32
Joined: Fri Jul 15, 2016 3:00 am

### Re: Electron Spin

When drawing out the Aufbau diagram and filling in the "orbitals" with the electrons, we want to make sure we follow both Hund's rule (electrons in the same subshell with occupy different orbitals) and Pauli Exclusion Principle (no more than two electrons per orbital). For example, when we fill the 2p orbitals for Neon, we first draw 3 "up arrows" (2px1, 2py1, 2pz1), then 3 "down arrows" (2px2, 2py2, 2pz2). If the last arrow that we draw is down, as in Neon, the 4th quantum number is -1/2.

If we are filling in orbitals and the last arrow we draw is up, for example in Carbon (2px1, 2py1), the 4th quantum number is +1/2.