Metals and Non-metals
Metals and non-metals tests the reactivity series more than it tests memorised properties, and extraction and corrosion questions come straight out of that ranking.
Physical and chemical properties
Metals are lustrous, malleable, ductile, sonorous and conduct heat and electricity; the exception is mercury, a liquid. Graphite is a non-metal that conducts. Metals form basic oxides; non-metal oxides are acidic. A metal displaces hydrogen from dilute acids only if it lies above hydrogen in the series.
Reactivity series
K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au. A higher metal displaces a lower one from a solution of its salt. Gold, silver and copper occur native; potassium, sodium, calcium and aluminium are never found free and are extracted by electrolysis of their molten compounds; zinc, iron and lead are obtained by reducing their oxides with carbon.
Extraction
Concentration of the ore → roasting (sulphide ores heated in air, e.g. 2ZnS + 3O₂ → 2ZnO + 2SO₂) or calcination (carbonate ores heated without air) → reduction to crude metal → refining, usually by electrolysis.
Corrosion and alloys
Rusting needs both oxygen and water; salt accelerates it. Prevention: painting, galvanising (zinc coating), alloying, chromium plating. Alloys: brass (Cu–Zn), bronze (Cu–Sn), solder (Pb–Sn), steel (Fe–C).
Worked example
A zinc rod is placed in copper sulphate solution. Zinc lies above copper, so Zn + CuSO₄ → ZnSO₄ + Cu; the blue colour fades and a red-brown deposit of copper appears on the rod.
Traps
Concluding aluminium is unreactive because it looks inert - it is protected by a thin oxide layer. Claiming iron reacts with cold water; it needs steam. Forgetting that sodium and aluminium cannot be obtained by carbon reduction.