Quantization four-state case

The spin angular momentum of an electron can have only certain specific values. Spin is quantized. Like the z component of orbital angular momentum, has 2s + 1 possible values. In the case of the electron, s =, so the only possible values of iMj are — and +. The specification of an electrons spin therefore represents two other quantum numbers that can be used to label the state of that electron. In practice, however, it is convenient to not specify s, because it is always for electrons. This gives us a total of four quantum numbers the principal quantum number n, the orbital angular momentum quantum number f, the orbital angular momentum z component m, and the spin angular momentum (z component) m. These are the only four quantum numbers needed to specify the complete state of an electron. 

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