Spin orbit coupling/Filling order/Nucleus

[em3ry]

Which tends to fill first:

p3/2 or p1/2?
d5/2 or d3/2?

And why is there no spin orbit coupling in the nucleus?

 

[dRic2]

I just googled it and came to this link https://chemistry.stackexchange.com/questions/58135/shape-of-the-p1-2-orbital/58442#58442. If you scroll to the first answer there is a picture. Judging from that picture I guess p1/2 has a slightly lower energy then 3/2 so I guess it will be filled first. Same goes for d orbitals. This for an isolated atoms, if you have a crystal overlap will occur and it is difficult to say a priori what would happen.

I don't understand your question about the nucleus.

 

[em3ry]

(Your software messed up the images a little bit)
Electron energy levels with spin orbit coupling:

Nuclear energy levels:

https://vignette.wikia.nocookie.net...g_order.svg/revision/latest?cb=20210106233016

https://vignette.wikia.nocookie.net...g.Order.svg/revision/latest?cb=20210106112220

 

[dRic2]

If you spend a few lines to actually explain your question someone might help you.

 

[em3ry]

As can be seen in the image above each electron energy level is split into 2. (e.g. 3/2 and 5/2.) But the nucleus has no such splitting

 

[snorkack]

Actually, vice versa.
Electrons have very weak spin-orbit splitting for small elements, so that for example 2p orbitals are first filled by 3 unpaired electrons, to N - irrespective of any 2p1/2 vs 2p3/2 difference.
Whereas nuclei have a strong spin-orbit splitting, so "1p" is split into "1p3/2" and "1p/2"