Quantum Numbers

[Harjot Manku 1C]

If the n (principle quantum number) is 3, then l (angular momentum quantum number) is 2. Which is a d-orbital. Where is the d oribtal when you have something like a 3s3p^3?

[Chem_Mod]

It's present, but just not occupied for the instance you provided.

Since orbitals are filled from lowest energy to highest energy, and 3d orbitals are higher in energy than 4s ones, 4s ones are occupied first.

[Joshua Xian 1D]

Why is the ms quantum number ±1/2? (How did people decide on the number 1/2 and not some other number?)

[Ya Gao]

To the question about d orbital, 3d orbital comes after 4s orbital. About where different orbitals are, you can refer to the energy level of different orbitals on page 43. About why electron spin is +-1/2, I believe the values are derived from experiment... but exactly why +- 1/2, I have no idea :(

[Sonja Kobayashi 1H]

Hello!
I believe that it is +1/2 snd -1/2 because the signs represent the orientation of the spinning electron. The negative indicates that the electron is spinning downwards while the positive 1/2 represents the electron spinning upwards. I hope that helps!