Metals and Non-metals
What the exam tests
Metals and Non-metals tests physical and chemical differences, the reactivity series, ionic bonding, extraction of metals, corrosion and alloys. BSEB papers often ask you to predict a displacement reaction and to name the reducing agent in a metallurgical step.
Core rules
- Reactivity order: K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Hg > Ag > Au.
- Metals lose electrons to form cations; non-metals gain electrons to form anions. The resulting ionic compounds have high melting points and conduct when molten or dissolved.
- Metal oxides are generally basic; non-metal oxides are acidic. Al2O3 and ZnO are amphoteric and react with both acids and bases.
- Metallurgy: concentrate the ore, then roast a sulphide or calcine a carbonate, reduce the oxide, and refine the metal.
- Roasting uses excess air on sulphide ores; calcination heats carbonate ores in limited air.
- Carbon reduces oxides of metals below it in the reactivity series; very reactive metals such as sodium are obtained by electrolysis.
- Corrosion is attack by moisture and air. Prevention includes painting, oiling, galvanising and alloying.
Worked example
Explain the thermite reaction: Fe2O3 + 2Al → 2Fe + Al2O3 + heat. Aluminium is above iron in the reactivity series, so it displaces iron from its oxide. The reaction is highly exothermic; molten iron is used to weld railway tracks. Aluminium is oxidised and iron is reduced.
Traps that cost marks
- Saying copper reacts with dilute hydrochloric acid; it does not, because it is below hydrogen.
- Calling galvanisation a tin coating; it is a zinc coating.
- Confusing roasting (sulphide) with calcination (carbonate).
- Forgetting that gold and silver occur in the native state.