This quantum number describes the behavior of the electrons in the magnetic field. We know that the movement of electrical charge is always associated with magnetic field. Since the revolving electron possesses angular momentum, it will give rise to a very small magnetic field, which will interact with the external magnetic field. Under the influence of external magnetic field, the electrons in a given sub-level will orient themselves in some preferred regions of space around the nucleus called orbitals. Thus, magnetic quantum number refers to the different orientations of the orbitals in space. It is designated by m. Since magnetism is due to the angular momentum, the value of m, depends on the value of l . For a given value of l, m can have integral values from -l through 0 to +l i.e.,
m = - l .…..0.…..+ l
Each value of m represents a particular orbital. For e.g.,
If l= 0, m has only one value, which is equal to 0 or s-subshell contains one orbital called s-orbital.
If l=1, m may be - 1, 0, +1 or p-subshell contains three orbitals called p- orbitals.
If l=2, m may be -2, -1, 0, +1, +2 or d-subshell contains five orbitals called d-orbitals.
Similarly, it can be shown that f-subshell can have seven orbitals. The number of orbitals in a subshells are given below:
It can be generalized that there are (2l + 1) values of m for each value of l and hence (2l +1) orbitals of each sub-level in a principal energy level.
