What you’ll learn5 learning objectivesChoose one objective for a focused lesson, or study the complete topic.28.3.1Terms: degenerate and non-degenerate d orbitals• Define/use: degenerate and non-degenerate d orbitalsSyllabus objective28.3.2d-orbital splitting• Describe the splitting of degenerate d orbitals into two non-degenerate sets of d orbitals of higher energy, and use of Δ E in:: (a) octahedral complexes, two higher and three lower d orbitals; (b) tetrahedral complexes, three higher and two lower d orbitalsSyllabus objective28.3.3Why transition elements form coloured compounds• Explain why transition elements form coloured compounds in terms of the frequency of light absorbed as an electron is promoted between two non-degenerate d orbitalsSyllabus objective28.3.4Ligand effects on orbital splitting• Describe, in qualitative terms, the effects of different ligands on Δ E, frequency of light absorbed, and hence the complementary colour that is observedSyllabus objective28.3.5Colours of Cu(II) and Co(II) complexes• Use the complexes of copper( II) ions and cobalt(II) ions with water and ammonia molecules and hydroxide and chloride ions as examples of ligand exchange affecting the colour observedSyllabus objective