The total spin of an Mg atom is zero and remains zero after absorption or emission of a photon. To which states can one of the electrons in the outer shell get by absorption of a single photon: 4s, 5s, 3p, 4p, 3d, 4d?
2. The attempt at a solution
I am not sure which of the states are possible. My ideas so far: When a photon is absorbed by one of the two electrons in the outer shell, the electron has a higher energy. But both electrons in the outer shell are in the state 3s (one with spin up, and the other with spin down). On the other hand, all states given above represent states with higher energy, so that all states should be possible. Is that true? Or do I missing something? I guess my answer is wrong because I ignored the total spin. But we have not discussed in class how the total spin is computed and how it is related to the energy of an atom.
Any help is very appreciated!