Electronic configuration of Mn is (Z=25)=[Ar]3d54s2 ∴ Electronic configuration of Mn4+ is Mn4+=[Ar]3d3 Thus, Mn4+ has 3 -unpaired electron and its spin only magnetic moment (µ) is, µ=√n(n+2)BM where, n= number of unpaired electrons. µ=√3(3+2).BM⇒µ=√15=3.87BM≈4BM