Magnetic momentum of an M^=3 ion is (35)^1/2 .

then no. of electrons in d orbital of m element will be ?

35^1/2  gives 5 unpaired electrons using magnetic moment= (n*(n+2))^1/2 and d has 5 orbitals, if in the question it is +3 (typing mistake done by you) charge then the metal should have 8 electrons (=5present+3 lost )in outer cell out of which 2 will be in S orbital so finally d has 6 electrons.

Thanks & Regards

Vikash Kumar, 

askIITians Faculty

B.Tech, IIT Delhi