On a Tanabe Sugano diagram, what is plotted on the y-axis?

On a Tanabe-Sugano diagram, the y-axis represents the energy levels of the electronic states of a transition metal complex, expressed in terms of E/B, where E is the energy of the electronic transition and B is the crystal field splitting parameter. This ratio helps to normalize the energy values and allows for the comparison of different complexes, especially those with varying geometry or metal centers.

The diagram itself is a valuable tool in understanding the electronic structure and splitting of d-orbitals in transition metal complexes, as it visually represents the energies involved in electronic transitions between these states as a function of the ligand field strength. This makes it particularly useful for predicting and rationalizing the colors and properties of coordination compounds based on their electronic configurations.

The other options, while relevant in certain contexts, do not pertain to the correct plotting in a Tanabe-Sugano diagram. Delta over B and Kf are important in other discussions of ligand field theory and stability constants, and pH is crucial for acid-base chemistry, but they do not represent the primary relationship conveyed by the Tanabe-Sugano plot.