For electronic configuration =[Ar]3d54s2 Group = number of valence electrons ‌‌‌‌‌‌ (∴ electrons in d and s-orbital) Electrons in d-orbital =5 and electrons in s-orbital =2 Group =5+2=7 [Ar]3d54s2=18+5+2=25‌‌‌‌‌‌ [For Mn (Manganese) group number =7]