The results of a theoretical study on the formation of the nitrogen cluster N10 from the ionic species N[+/5] and N[-/5] are presented. The possibility to form N8 from N[+/5] and N[-/3] has also been studied but no stable form was found. Structural and vibrational data are given for the different clusters. It is suggested that the anion N[-/5] might be stable enough to be synthesized. The calculations have been carried out using multiconfigurational self-consistent-field wave functions and second-order perturbation theory.