[Mn(H2O)6]2+:Mn2+=3d5. ∴ Number of unpaired electrons = 5 [Fe(H2O)6]2+:Fe2+=3d6 ∴ Number of unpaired electrons = 4 [Co(H2O)6]2+:Co2+=3d7 ∴ Number of unpaired electrons = 3 [Cr(H2O)6]2+:Cr2+=3d4 ∴ Number of unpaired electrons = 4 Minimum paramagnetic behaviour is shown by [Co(H2O)6]2+