Explains d orbital splitting in metal complexes due to electrostatic repulsion from ligands.
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Crystal field theory explains the energies of d orbitals in transition metal complexes by treating the ligands as negative point charges that electrostatically repel electrons in the metal's d orbitals. In an octahedral field the five d orbitals split into a lower set of three orbitals called t2g and a higher set of two called eg, separated by an energy gap called delta_o. The size of this gap depends on the metal, its oxidation state and the ligands. The splitting explains the colours, magnetism and stability of complexes. The theory is a simplified electrostatic model that ignores covalent bonding.
Key ideas: In an octahedral field, energy of t2g is lowered by 0.4 delta_o and eg is raised by 0.6 delta_o. Crystal field stabilization energy equals (0.4 times number in t2g minus 0.6 times number in eg) delta_o plus pairing terms. Tetrahedral splitting is about 4/9 of octahedral and always high spin, with the order reversed: e lower, t2 higher.
Common mistakes and connections: Typical errors: reversing t2g and eg, forgetting that in tetrahedral complexes the lower set is e, using the model to claim it describes covalency, and ignoring the spin state in CFSE. The theory does not explain the spectrochemical series order for ligands like CO, which is explained by pi bonding in ligand field theory. Links to colour, magnetism and high and low spin.
In an octahedral field the d orbitals split into a lower t2g set at -0.4 Delta and a higher eg set at +0.6 Delta. The interactive lesson shows this as a live animation or chart.
The titanium(III) complex [Ti(H2O)6]3+ has one d electron in t2g, which absorbs visible light and gives the complex its purple colour.
Explains d orbital splitting in metal complexes due to electrostatic repulsion from ligands.
Crystal Field Theory is a advanced topic in Bonding & Molecular Structure. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Bonding & Molecular Structure first: Ligands, Coordination Number, Chelation.
The next topics in Bonding & Molecular Structure are Spectrochemical Series and High Spin and Low Spin Complexes.
Yes. The interactive lesson includes a self-check question on Crystal Field Theory, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Crystal Field Theory is topic 92 of 104 in Bonding & Molecular Structure.