How do you determine the possible quantum numbers for an atom?

The quantum numbers can be used to describe a specific electron in an atom of that element. There are four quantum numbers:

n, the principal quantum number, which describes the shell of an electron; l, the Azimuthal quantum number, which describes the subshell of an electron; ml, the magnetic quantum number, which describes/specifies the orbital an electron is in; and ms, the spin quantum number, which describes the spin of the electron.

For example, if I was told that I had quantum numbers for a valence shell electron in the ground state for nitrogen were n=2, l=1, ml = - 1 and ms = + 12 then:

The n=2 tells me that we are describing a shell 2 electron. the l=1 describes the subshell as p.

I now know we are talking about a shell 2, p subshell energy level for the electron. The ml = - 1 would indicate the specific orbital in the p-subshell (there are three possible p-orbitals in this p-subshell with ml values = - 1, 0, + 1) We have specified the first 2p-subshell orbital with the ml value = - 1. The spin quantum number of + 1/2 indicates one of two possible spin quantum numbers (+1/2 and - 1/2) for the two electrons that can fill this specific orbital in this specific subshell and shell.