A report is given of a study of the resonant contribution to the scattering length for x-rays, evaluated using an atomic picture of the electrons. Armed with the scattering length one can calculate the attenuation coefficient, dichroic signal and cross-sections for the elastic and inelastic scattering of x-rays by magnetic materials. The formulation is more finely honed than the one used in two previous studies. The additional information in the scattering length relates to the spins of the electrons in the unfilled valence shell. For the and configurations, tables of Racah unit spherical tensors are provided for ground states determined by Hund's rules.