The Crystal Field Theory experiment illustrates the effects on a metal d orbital energies of moving a set of negative point charges close to a metal ion. As one would expect, the energies of the d orbitals rise as the negative charges approach the metal ion, owing to the repulsions between the d orbital electrons and the surrounding charge.
If the surrounding negative charge is spherically symmetric, all five d orbitals are equally affected. In practice, the surrounding negative charge is never spherically distributed, because the charge is associated with specific ions that occupy specific positions.
The consequence is each d orbital is affected differently, and how a particular d orbital is affected depends upon the geometry of the surrounding point charges. This effect is clearly seen in the splitting of the energy levels for the five d orbitals. When point charge enters a region of high electron density, the orbital energy rises significantly owing to the repulsion between the electron and the point charge. When the point charge approaches the ion along a nodal surface, the orbital energy does not increase as greatly.
The extent of the splitting in energies is represented by the splitting energy ?.