Demonstrations on Paramagnetism with an Electronic Balance

Abstract

The paramagnetism of inorganic compounds is related to the number of unpaired electrons of the atoms. Thus, can be used to stablish oxidation states and bonding properties. A simple set-up made with a powerful neodymium magnet over the plate of an electronic balance allows measuring the force of attraction over a solid substance or a solution in a test tube. The lack of paramagnetism of salts whose elements have complete electronic subshells and the comparison of the force of attraction over compounds of the same metal in different oxidation state (as potassium ferro and ferricianide, or salts of Cu(I) and Cu(II)), allows to confirm that paramagnetism is associated to the number of unpaired electrons. The splitting of the five d orbitals according to the ligand field theory allows to justify the different behavior of some Fe(II) or Fe(III) compounds. The graph of the force of attraction over each mole versus the number of unpaired electrons fits to the second grade polynomial k(N2+2N) predicted by the the...