Metals, Non-metals and Their Compounds
Metals, non-metals and their compounds
This domain tests the reactivity series, displacement, extraction of metals, corrosion, alloys and the chemistry of common non-metals and their oxides. GCE O-Level questions often link reactivity to extraction method and to observations in reactions.
Core rules
- The reactivity series places potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver and gold in order. More reactive metals displace less reactive metals from solutions of their salts.
- Metals above carbon in the series are extracted by electrolysis of molten compounds; metals below carbon can be reduced by carbon. Iron is extracted in a blast furnace using carbon monoxide; aluminium is extracted by electrolysis of molten aluminium oxide dissolved in cryolite.
- Rusting requires both oxygen and water. Sacrificial protection uses a more reactive metal such as zinc; painting, oiling and alloying also prevent corrosion.
- Non-metal oxides are usually acidic; metal oxides are usually basic. Amphoteric oxides such as aluminium oxide react with both acids and alkalis.
- Common non-metals include oxygen, hydrogen, chlorine, nitrogen, sulfur and carbon. Chlorine bleaches damp litmus; sulfur dioxide is acidic and contributes to acid rain.
Worked example
A piece of zinc is placed in blue copper(II) sulfate solution. Describe the reaction and write the ionic equation.
Reasoning: zinc is more reactive than copper, so it displaces copper from the solution. The blue colour fades as Cu2+ ions are removed, and a red-brown deposit of copper forms on the zinc. Zinc dissolves to form Zn2+. The ionic equation is Zn(s) + Cu2+(aq) -> Zn2+(aq) + Cu(s). This is a redox reaction: zinc is oxidised and copper(II) ions are reduced.
Traps that cost marks
Aluminium cannot be extracted by carbon reduction because it is more reactive than carbon. Rusting is not caused by oxygen alone. Stainless steel is an alloy, not pure iron. Do not confuse displacement with neutralisation. Amphoteric oxides react with both acids and alkalis, so do not call them simply basic.
Key points
- Reactivity determines extraction method and displacement reactions.
- Metals above carbon are extracted by electrolysis.
- Rusting needs both oxygen and water.
- Metal oxides are usually basic; non-metal oxides are usually acidic.
- Displacement is a redox reaction.