(A Level) Transition element complexes: colour, isomerism and stability constants

Learning objectives

Describe how the five degenerate d orbitals split into two non-degenerate sets in octahedral and in tetrahedral complexes

Explain the colour of a complex from absorption of visible light as electrons move between split d orbitals, and how changing the ligand changes ΔE, the frequency absorbed and the colour seen

Describe cis–trans isomerism in square planar and octahedral complexes such as [Pt(NH₃)₂Cl₂] and [Co(NH₃)₄(H₂O)₂]²⁺, optical isomerism in complexes of bidentate ligands such as [Ni(en)₃]²⁺, and deduce whether each isomer is polar

Write Kstab expressions for complex formation (leaving out water), carry out calculations with them, and use Kstab values to explain the direction of ligand exchange