How do you determine if an atom has a diamagnetic (ground state) electron configuration?
By checking out the arrangement of it's valence electrons in it's outer most orbital.
The arrangement of the electrons in the outermost orbital i.e
A dimagnetic atom has all the electrons arranged in pairs
Where as a paramagnetic atom have more than 1 umpaired electrons.
And the magnetic moment of paramagnetic atom can be calculated by the formula.
Hope it will help you.