Economic importance of the first-series elements

Together these ten elements make up about 7 % of the mass of the Earth's crust (iron alone is about 5 %; the others are present in very small percentages, from about 0.003 % for scandium to under 1 % for each of the rest), yet their importance is very large.

• Scandium (Sc): found in very small amounts spread over wide areas. A little scandium added to aluminium gives a light, very hard alloy used for fighter-jet parts. It is added to mercury-vapour lamps to give light close to sunlight, so it is used for night television photography.
• Titanium (Ti): as strong as steel but less dense. Its alloys with aluminium keep their strength at high temperature (where aluminium alone softens), so they are used in aircraft and space shuttles. Because titanium is chemically inert and the body does not reject it or get poisoned by it, it is used in dental implants and artificial joints. Titanium dioxide (TiO₂) is used in sun-protection cosmetics: its nanoparticles block ultraviolet rays.
• Vanadium (V): adding a little vanadium to steel gives a very hard alloy that resists corrosion, used for car springs. Vanadium(V) oxide (V₂O₅) is used as a pigment in ceramics and glass, as a catalyst, and in making strong magnetic materials.
• Chromium (Cr): an active metal, yet it resists attack by air. Its oxide film has a larger molecular volume than the metal atoms it forms from, so it is a continuous, non-porous layer that stops further reaction with oxygen. Chromium is used in plating and in steel for pipes and surgical tools. Chromium(III) oxide (Cr₂O₃) is used in pigments; potassium dichromate (K₂Cr₂O₇) is an oxidizing agent.
• Manganese (Mn): brittle, so it is never used as the pure metal but in alloys or compounds. Ferromanganese is harder than steel and is used for railway tracks; aluminium–manganese alloys make drink cans. MnO₂ is a strong oxidizing agent used in dry cells; KMnO₄ is an antiseptic; MnSO₄ is a fungicide.
• Iron (Fe): the most important metal in heavy industry. Finely divided iron is the catalyst of the Haber–Bosch process for ammonia and of the Fischer–Tropsch conversion of water gas (CO + H₂) into fuel.
• Cobalt (Co): like iron it can be magnetized, so it is used for magnets; it is used in modern car batteries. Cobalt has twelve radioactive isotopes, of which cobalt-60 is the most important: it gives gamma rays of high penetrating power and is used to preserve food, test the quality of industrial products, detect cracks and weak welds, and diagnose and treat tumours.
• Nickel (Ni): used in rechargeable nickel–cadmium batteries; forms hard steels that resist rust and acids; nickel–chromium alloys make heating coils and electric furnaces because they resist corrosion at high temperature; used to plate other metals (to protect them from oxidation and give a good appearance); finely divided nickel is the catalyst for hydrogenation of oils.
• Copper (Cu): the first metal discovered by humans; copper–tin alloy is bronze. Being an excellent conductor it is used for electric cables and coins. CuSO₄ is an insecticide and fungicide and is used in water purification. Fehling's solution (a copper(II) compound) detects glucose: its blue colour changes to orange/red.
• Zinc (Zn): used to galvanize iron against rusting. ZnO is used in paints, rubber and cosmetics; ZnS is used in luminous paints and X-ray screens.