neutral atoms before the d subshell. For example, the Ti²⁺ ion has the ground-state configuration [Ar]3d² with a d electron count of 2, even though the total number of electrons is the same as the neutral calcium atom which is [Ar]4s².

In coordination complexes between an electropositive transition metal atom and an electronegative ligand, the transition metal is approximately in an ionic state as assumed in crystal field theory, so that the electron configuration and d electron count are those of the