Spin Magnetic Quantum Number

[OrAmar-1L]

Can someone explain to me the concept of the fourth quantum number we learned in Wednesday's lecture? The whole spin-up and spin-down thing didn't really make sense to me. Thank you!

[Brynne Keyser 1B]

The fourth and final quantum number is used to indicate the orientation of the two electrons in each orbital. The values for ms are +1/2 and -1/2. An atom is the most stable when its electrons have the lowest possible energy.

Hope this helps!

[Nina_A_Section1E]

Since e- spins on its axis it has an angular momentum and orbital angular momentum, the spin magnetic quantum number describes the angular momentum of the e-. This is a vector, which is why it has magnitude (1/2) and a direction (+/-)

Since each orbital holds 2 e-, 1 will have a spin +1/2, and the other -1/2. Because e- fill orbitals before pairing up, the first e- in an orbital will always be the +1/2, and then the 2nd -1/2. When there are 2 e- in an orbital, it will spin in opposite directions.

https://chem.libretexts.org/Under_Const ... tum_Number)
Here's a nice diagram of it shows the spinning in relation to the magnetic field