High Quality Content by WIKIPEDIA articles! The d electron count is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex. The d electron count is an effective way to understand the geometry and reactivity of transition metal complexes. The formalism has been incorporated into the two major models used to describe coordination complexes; ligand field theory which is an application of molecular orbital theory to transition metals and crystal field theory which has roots in VSEPR theory.