Maximum oxidation states shown by a transition element =(n−1)d‌‌ unpaired electrons +ns electrons. For 3d3,4s2, Maximum oxidation state =3+2=5 For 3d5,4s1 Maximum oxidation state =5+1=6 For 3d5,4s2 Maximum oxidation state =5+2=7 For 3d6,4s2, Maximum oxidation state =4+2=6 Thus, 3d5,4s2 configuration shows the highest oxidation state.