Magnetic Quantum Number (ml): ml = -l, ..., 0, ..., +l. Specifies the orientation in space of an orbital of a given energy (n) and shape (l). This number divides the subshell into individual orbitals which hold the electrons; there are 2l+1 orbitals in each subshell. Thus the s subshell has only one orbital, the p subshell has three orbitals, and so on. Spin Quantum Number (m s): m s = +Â½ or -Â½. Specifies the orientation of the spin axis of an electron.