Electronic absorption spectra Allowed vs forbidden transitions

Factors affecting the magnitude of ) (CrystalField Splitting)● Charge on the metal. For first row transition elements ) Ovaries fromabout 7,500 cm -1 to 12,500 cm -1 for divalent ions and 14,000 cm -1 to25,000 cm -1 for trivalent ions.● Position in a group. ) Ovalues for analogous complexes of metal ionsin a group increase by 25% to 50% on going from one transition seriesto the next. This is illustrated by the complexes [M(NH 3) 6] 3+ where )values are 23,000 cm -1 for M=Co; 34,000 cm -1 for M=Rh and 41,000cm -1 for M=Ir.● Geometry and coordination number. For similar ligands ) twill beabout 4/9 ) O. This is a result of the reduced number of ligands andtheir orientation relative to the d orbitals. Recall that the energyordering of the orbitals is reversed in tetrahedral complexes relative tothat in the octahedral case.● Identity of the ligand. The dependence of ) on the nature of theligand follows a regular order, known as the spectrochemical series, forall metals in all oxidation states and geometries.