Magnetic susceptibility and the spin-only formula

   We begin the discussion of magnetochemistry with the socalled spin-only formula, an approximation that has limited, but useful, applications. Paramagnetism arises from unpaired electrons. Each electron has a magnetic moment with one component associated with the spin angular momentum of the electron and (except when the quantum number l = 0) a second component associated with the orbital angular momentum. For many complexes of first row d-block metal ions we can ignore the second component and the magnetic moment, μ , can be regarded as being determined by the number of unpaired electrons, n (equations 1.1 and 1.2). The two equations are related because the total spin quantum number S = n/2.

                                  (1.1)

                                  (1.2)

   The effective magnetic moment, μ_eff, can be obtained from the experimentally measured molar magnetic susceptibility,