Why Transition Metals Form Coloured Compounds and Act as Catalysts
Part of Transition Metals (HT) — GCSE Chemistry
This how it works covers Why Transition Metals Form Coloured Compounds and Act as Catalysts within Transition Metals (HT) for GCSE Chemistry. Revise Transition Metals (HT) in Atomic Structure for GCSE Chemistry with 20 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 3 of 11 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 3 of 11
Practice
20 questions
Recall
20 flashcards
⚙️ Why Transition Metals Form Coloured Compounds and Act as Catalysts
Unlike the main group metals (Groups 1 and 2), transition metals have partially filled inner electron sub-shells (the d-orbitals, for those studying beyond GCSE). This gives them two remarkable properties. First, when light hits a transition metal compound, some wavelengths of visible light are absorbed as electrons move between different energy states within these inner shells — the remaining wavelengths are reflected back to our eyes as colour. Different transition metals have differently spaced energy levels, absorbing different wavelengths, which is why copper compounds are blue, iron(III) compounds are orange-brown, and potassium permanganate is purple. Second, transition metals can form ions with variable charge (e.g., Fe²⁺ and Fe³⁺). This ability to switch between oxidation states makes them excellent catalysts: they can temporarily accept electrons from one reactant and then donate them to another, effectively shuttling electrons between molecules and speeding up reactions without being permanently changed. This is why iron catalyses the Haber process and platinum catalyses reactions in catalytic converters.