How metals and non-metals differ and how metals are extracted
Metals are usually shiny, hard, malleable (can be beaten into sheets), ductile (can be drawn into wires) and good conductors of heat and electricity. Non-metals are usually dull, brittle and poor conductors. There are exceptions: mercury is a liquid metal, sodium is soft enough to cut with a knife, and graphite is a non-metal that conducts electricity. Metals react with oxygen to form basic oxides, while non-metals form acidic oxides. Aluminium oxide and zinc oxide are amphoteric.
The reactivity series arranges metals from most reactive, like potassium and sodium, to least reactive, like gold. A more reactive metal displaces a less reactive one from its salt solution. Metals and non-metals form ionic compounds by transferring electrons; these have high melting points and conduct electricity when molten or dissolved. Extraction depends on reactivity: highly reactive metals are obtained by electrolysis, moderately reactive ones by roasting or calcination followed by reduction with carbon, and unreactive ones often occur free. Iron rusts in moist air, and corrosion is prevented by painting, oiling, galvanising and alloying.
Why it matters
Metals and their alloys build vehicles, bridges, wires, utensils and jewellery. Stainless steel resists rust, brass and bronze are strong alloys, and aluminium is light enough for aircraft. Understanding extraction explains why aluminium was once precious. Preventing corrosion saves large amounts of money in infrastructure and transport.
Key terms
- Malleability
- The property of a metal that allows it to be beaten into thin sheets.
- Reactivity series
- A list of metals arranged in order of decreasing chemical reactivity.
- Alloy
- A uniform mixture of a metal with other metals or a non-metal.
- Amphoteric oxide
- An oxide that reacts with both acids and bases to form salt and water.