Why Transition Metals Form Coloured Compounds and Act as Catalysts

⚙️ Why Transition Metals Form Coloured Compounds and Act as Catalysts

Unlike the main group metals (Groups 1 and 2), transition metals have two remarkable properties. First, transition metal ions absorb some wavelengths of visible light, reflecting back the remaining wavelengths as colour. Different transition metals absorb 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 ion charges makes them excellent catalysts: they can temporarily accept electrons from one reactant and then donate them to another, speeding up reactions without being permanently changed. This is why iron catalyses the Haber process and platinum catalyses reactions in catalytic converters.