Crystal field theory

Definition

Crystal Field Theory (CFT) describes the breaking of degeneracies of electronic orbitals in transition metal complexes due to the presence of ligands. It explains how the arrangement of ligands around a central metal ion affects the energy levels and properties like color and magnetism.

5 Must Know Facts For Your Next Test

1. In an octahedral field, $d$-orbitals split into two sets: $e_g$ (higher energy) and $t_{2g}$ (lower energy).
2. The difference in energy between these sets is called the crystal field splitting energy ($\Delta_0$).
3. Strong-field ligands cause larger splitting ($\Delta_0$), often leading to low-spin complexes, whereas weak-field ligands cause smaller splitting, often resulting in high-spin complexes.
4. According to CFT, the color of coordination compounds arises from electronic transitions between split $d$-orbitals.
5. Magnetic properties of coordination compounds can be predicted by examining unpaired electrons in these split orbitals.

Review Questions

• What causes the splitting of $d$-orbitals in Crystal Field Theory?
• How does the strength of a ligand affect the spin state of a complex?
• Why do coordination compounds exhibit different colors according to CFT?

Related terms

Ligand Field Theory: An extension of Crystal Field Theory that incorporates molecular orbital theory to better explain bonding in coordination compounds.

$d$-Orbital Splitting: The division of degenerate $d$-orbitals into groups with different energies due to ligand interactions in a coordination compound.

High-Spin Complex: A coordination complex where electrons occupy higher-energy orbitals first, resulting in more unpaired electrons due to smaller crystal field splitting.