What Are the Transition Metals?
The transition metals occupy the large central block of the periodic table (Groups 3–12), between the reactive metals of Groups 1–2 and the non-metals of Groups 13–18.
Well-known examples include: iron (Fe), copper (Cu), zinc (Zn), nickel (Ni), chromium (Cr), manganese (Mn), titanium (Ti), gold (Au), silver (Ag).
Physical Properties
Compared to Group 1 (alkali metals), transition metals are:
- Much harder and stronger
- Much higher melting points (e.g. iron melts at 1538°C vs sodium at 98°C)
- Denser (iron: 7.9 g/cm³ vs sodium: 0.97 g/cm³)
- Less reactive — they don't react explosively with water or air
These properties make them ideal structural materials (iron and steel in buildings; titanium in aircraft and medical implants).
Variable Oxidation States
A key feature of transition metals is their ability to form ions with different charges (oxidation states):
- Iron: Fe²⁺ (iron(II)) and Fe³⁺ (iron(III))
- Copper: Cu⁺ and Cu²⁺
- Manganese: Mn²⁺, Mn³⁺, Mn⁴⁺ and even Mn⁷⁺
This is different from Group 1 metals, which only ever form 1+ ions.
Coloured Compounds
Transition metal compounds are characteristically coloured:
| Compound | Colour |
|---|---|
| Copper(II) sulfate solution | Blue |
| Iron(III) oxide (rust) | Red-brown |
| Potassium manganate(VII) | Deep purple |
| Chromium(III) sulfate | Green |
| Nickel(II) sulfate | Green |
These vivid colours are used as pigments — the blue of ancient Egyptian lapis lazuli and the green of old copper roofs (verdigris) are both transition metal compounds.
Transition Metals as Catalysts
Transition metals often act as catalysts — substances that speed up reactions without being permanently changed:
- Iron: catalyst in the Haber process to make ammonia (fertilisers)
- Nickel: catalyst in manufacturing margarine from vegetable oil
- Platinum and rhodium: catalytic converters in car exhaust systems
- Manganese(IV) oxide: decomposes hydrogen peroxide
Real world: Iron and steel in construction
Iron (Fe) is extracted from ore and converted to steel (iron + small amounts of carbon). Steel's strength and malleability make it the dominant structural material for skyscrapers, bridges, and car bodies. Iron's position as a transition metal gives it a high melting point (1538 °C) and density — ideal for heavy-duty engineering. Rusting (iron(III) oxide, Fe₂O₃) is prevented by painting, galvanising, or stainless steel alloying.
Real world: Copper in electrical wiring
Copper (Cu) is the most widely used electrical conductor. Its transition metal properties — high conductivity (due to free electrons), high ductility, and resistance to corrosion — make it perfect for electrical cables in homes, electronics, and power networks. Copper pipes carry water in plumbing because copper is durable and does not corrode easily in water.
Real world: Platinum catalyst in car exhausts
Car catalytic converters use platinum (Pt) and rhodium (Rh) as catalysts to convert toxic exhaust gases (CO, NOₓ, unburned hydrocarbons) into safer CO₂, N₂, and H₂O. These transition metals can hold gas molecules on their surface, promoting reactions without being consumed themselves. Without transition metal catalysts, exhaust emissions would be far more polluting.
Where do you see this in real life? Steel buildings and bridges, copper electrical cables, iron in your blood (haemoglobin), titanium in hip replacement implants, and the catalytic converter in every modern car — all rely on transition metal properties.