Question

If Hund's rule is not followed, magnetic moment of Cr is :

Answer 1

According to Hund's rule electrons are distributed among the orbitals of subshell in such a way as to give maximum number of unpaired electron with parallel spin, i.e., in a subshell pairing of electron will not start until and unless all the orbitals of that subshell will get one electron each with same spin.
So, $Cr$ have zero unpaired electron and Magnetic moment is zero.