- In a metal complex, ligands make the metal’s dd-orbitals split into higher and lower energy levels.
- The strength of the ligand decides how big the gap (Δ\Delta) is:
- Weak ligands → small gap.
- Strong ligands → large gap.
- Small gap → electrons spread out (high-spin).
- Large gap → electrons pair up (low-spin).
- The size of the gap also affects the color of the complex.
Stronger ligand = bigger splitting.
Weaker ligand = smaller splitting.