Bethe-
A namesake parameter of this theory is normalized by the Racah parameter on the x-axis of Tanabe-Sugano diagrams. That parameter's relation to the pairing energy determines whether complexes are "high spin" or "low spin" in this theory. Oddly, the neutral molecule carbon monoxide induces the largest value for that parameter, placing it rightmost on the spectrochemical series, which reveals the limitations of this theory as it predicts the opposite due to being an ionic model that disregards covalent interactions. This theory is used to explain the color and magnetic properties of coordination compounds. For 10 points, name this Hans Bethe- developed theory that describes the electronic structure of d-block transition metals.
A namesake parameter of this theory is normalized by the Racah parameter on the x-axis of Tanabe-Sugano diagrams.
crystal field theory [or CFT]