[en] Negative ions homologous to N⁻ are interesting systems, since there are several bound terms within the ground configuration. The forbidden transitions between them, often dominated by the magnetic dipole contributions, are affected by term mixing—a relativistic effect. When increasing the nuclear charge in the homologous sequence of negative ions, this effect increases. In this paper we use systematic multiconfiguration Dirac–Hartree–Fock calculations to study these effects and predict affinities, level splittings and transition rates between bound states of N⁻, P⁻, As⁻, Sb⁻ and Bi⁻. By monitoring the line strengths we are able to predict the deviation from the non-relativistic LS-coupled values for transitions between levels of the lowest ³P term. For Sb⁻ the ¹D term is also bound, and the prediction for the rates of its transition to the ³P-levels is a challenge for theory. For Bi⁻ less is known experimentally and we analyze its structure and the relativistic contributions to it. (paper)