# What quantum numbers refer to a 7s orbital?

The $7 s$ orbital can hold as many as two electrons with principal quantum number $n = 7$ and orbital angular momentum quantum number $l = 0$.
The designation $7 s$ strictly applies only to one-electron (so-called hydrogenic) atoms such as $H , H {e}^{+} , L {i}^{2 +} ,$ etc. However, the designation is commonly used to indicate the approximate wave functions of many-electron atoms as well.
All of the electrons in an atom must have unique sets of quantum numbers. Therefore, if an orbital contains two electrons, then one of them must have a spin magnetic quantum number ${m}_{s} = + \frac{1}{2}$ and the other ${m}_{s} = - \frac{1}{2}$.