Abstract In this paper the π-acceptor character of an isoelectronic series of ligands is analyzed quantitatively using ab-initio MO calculations and some criteria of MO theory that are widely known among inorganic chemists. The study describes a numerical scale in which the species can be ordered according to their donor/acceptor character and their chemical stability, as well as the possibility of making predictions about the behavior of hypothetical ligands. The results from MO calculations for ionized ligands can easily model the dynamics of the acceptor/donor character during a chemical process. We also emphasize the quickness of the calculations and the simplicity of the theoretical basis behind the analysis. Key Words: π acceptor ligandsDiatomic moleculesIsoelectronic series Ab-initio MO calculations