Metals and Non-Metals

What you'll learn

This topic examines the fundamental differences between metallic and non-metallic elements, their physical and chemical properties, and how these properties determine their uses. CXC CSEC Chemistry papers regularly test your ability to predict reactivity, explain extraction methods, and apply knowledge of the reactivity series to displacement reactions. Expect both structured questions and multiple-choice items on this content.

Key terms and definitions

Metal — an element that forms positive ions by losing electrons; typically lustrous, malleable, ductile, and a good conductor of heat and electricity.

Non-metal — an element that gains or shares electrons in reactions; usually poor conductors, brittle when solid, and have low melting and boiling points.

Reactivity series — an arrangement of metals in order of their reactivity with oxygen, water, and acids, from most reactive (potassium) to least reactive (gold).

Displacement reaction — a reaction in which a more reactive metal removes a less reactive metal from its compound.

Ore — a naturally occurring rock or mineral from which a metal can be economically extracted.

Reduction — the removal of oxygen from a compound, or the gain of electrons by an atom or ion.

Alloy — a mixture of two or more metals, or a metal with a non-metal, designed to improve properties.

Corrosion — the gradual destruction of a metal by chemical reaction with substances in its environment, such as oxygen and water.

Core concepts

Physical properties of metals and non-metals

Metals exhibit characteristic physical properties:

• Lustre: shiny appearance when freshly cut or polished (e.g., aluminium window frames in Caribbean buildings)
• Malleability: can be hammered into thin sheets without breaking (aluminium foil used in cooking)
• Ductility: can be drawn into wires (copper wiring throughout Trinidad and Tobago's electricity grid)
• High density: most metals are dense, with exceptions like sodium and potassium
• High melting and boiling points: most metals are solid at room temperature (mercury is the exception)
• Electrical conductivity: metals conduct electricity due to mobile delocalised electrons
• Thermal conductivity: efficient heat transfer makes metals ideal for cooking utensils
• Sonorous: produce a ringing sound when struck

Non-metals display contrasting properties:

• Dull appearance: no metallic lustre (except iodine and graphite)
• Brittle when solid: break or crumble under stress (sulphur, carbon)
• Low density: generally less dense than metals
• Low melting and boiling points: many are gases at room temperature (oxygen, nitrogen, chlorine) or have low melting points
• Poor conductors: insulators of heat and electricity (graphite is the notable exception)
• Non-sonorous: no ringing sound produced

Chemical properties and reactivity

Reaction with oxygen

Metals react with oxygen to form basic oxides:

• Magnesium + oxygen → magnesium oxide: 2Mg + O₂ → 2MgO
• Aluminium + oxygen → aluminium oxide: 4Al + 3O₂ → 2Al₂O₃
• Iron + oxygen → iron(III) oxide: 4Fe + 3O₂ → 2Fe₂O₃ (rust formation on steel drums in humid Caribbean climate)

Non-metals react with oxygen to form acidic oxides:

• Sulphur + oxygen → sulphur dioxide: S + O₂ → SO₂
• Carbon + oxygen → carbon dioxide: C + O₂ → CO₂
• Nitrogen + oxygen → nitrogen dioxide: N₂ + 2O₂ → 2NO₂

Reaction with water

Reactivity varies significantly:

• Potassium and sodium: react vigorously with cold water, producing hydrogen gas and metal hydroxides (highly exothermic)
  • 2Na + 2H₂O → 2NaOH + H₂
• Calcium: reacts steadily with cold water
  • Ca + 2H₂O → Ca(OH)₂ + H₂
• Magnesium: reacts very slowly with cold water, but rapidly with steam
  • Mg + H₂O (steam) → MgO + H₂
• Iron and zinc: react with steam only
• Copper, silver, gold: no reaction with water or steam

Non-metals generally do not react with water, though chlorine dissolves to form an acidic solution.

Reaction with dilute acids

Metals above hydrogen in the reactivity series displace hydrogen from dilute acids:

• Zinc + hydrochloric acid → zinc chloride + hydrogen: Zn + 2HCl → ZnCl₂ + H₂
• Magnesium + sulphuric acid → magnesium sulphate + hydrogen: Mg + H₂SO₄ → MgSO₄ + H₂

Metals below hydrogen (copper, silver, gold) do not react with dilute acids.

The reactivity series

The CXC CSEC Chemistry syllabus requires knowledge of this order (most to least reactive):

Potassium (K) Sodium (Na) Calcium (Ca) Magnesium (Mg) Aluminium (Al) Carbon (C) — non-metal included for extraction purposes Zinc (Zn) Iron (Fe) Lead (Pb) Hydrogen (H) — reference point for acid reactions Copper (Cu) Silver (Ag) Gold (Au) Platinum (Pt)

Memory aid: Please Send Charlie's Monkeys And Cats Zipping In Large Healthy Cages Safely Guarded Properly

Displacement reactions

A more reactive metal displaces a less reactive metal from its compound in solution or when heated with its oxide:

In solution:

• Zinc + copper sulphate → zinc sulphate + copper: Zn + CuSO₄ → ZnSO₄ + Cu
• Magnesium + iron(II) sulphate → magnesium sulphate + iron: Mg + FeSO₄ → MgSO₄ + Fe

With solid oxides (thermit-type reactions):

• Aluminium + iron(III) oxide → aluminium oxide + iron: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe
• Magnesium + copper(II) oxide → magnesium oxide + copper: Mg + CuO → MgO + Cu

No reaction occurs when a less reactive metal is added to a compound of a more reactive metal:

• Copper + magnesium sulphate → no reaction
• Silver + zinc chloride → no reaction

Extraction of metals from their ores

The position in the reactivity series determines the extraction method:

Very reactive metals (potassium to aluminium):

Extracted by electrolysis of molten compounds. Bauxite mining in Jamaica produces aluminium oxide (Al₂O₃), which undergoes electrolytic reduction:

• At cathode: Al³⁺ + 3e⁻ → Al
• At anode: 2O²⁻ → O₂ + 4e⁻

This process requires significant electrical energy, explaining why aluminium smelting facilities locate near cheap power sources.

Moderately reactive metals (carbon to lead):

Extracted by reduction with carbon or carbon monoxide in a blast furnace. Iron extraction from haematite (Fe₂O₃) in a blast furnace:

1. Hot air blown into furnace reacts with coke: C + O₂ → CO₂
2. Carbon dioxide reduced to carbon monoxide: CO₂ + C → 2CO
3. Carbon monoxide reduces iron oxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂
4. Limestone (CaCO₃) decomposes to remove impurities: CaCO₃ → CaO + CO₂
5. Calcium oxide reacts with silica: CaO + SiO₂ → CaSiO₃ (slag)

Zinc extraction from zinc blende (ZnS):

1. Roasting in air: 2ZnS + 3O₂ → 2ZnO + 2SO₂
2. Reduction with carbon: ZnO + C → Zn + CO

Unreactive metals (copper to platinum):

Found native (uncombined) in the Earth's crust or extracted by heating alone. Gold panning in Guyana exploits this property.

Uses of metals and alloys

Pure metals and their applications:

• Aluminium: window frames, aircraft construction, cooking foil, electricity cables (lightweight, corrosion-resistant)
• Copper: electrical wiring, water pipes, cooking vessels (excellent conductor, malleable)
• Iron: construction, bridges, tools (strong, abundant, low cost)
• Zinc: galvanising steel, sacrificial protection (protects iron from corrosion)
• Lead: car batteries, radiation shielding (dense, resists corrosion)

Common alloys:

Alloys are designed to improve properties like strength, corrosion resistance, or appearance:

• Steel (iron + carbon): construction beams, vehicle bodies, reinforcement bars in Caribbean concrete buildings. Different carbon percentages produce mild steel (0.15-0.3% C) or high-carbon steel (0.6-1.5% C)
• Stainless steel (iron + chromium + nickel): cutlery, kitchen sinks, medical instruments (resists corrosion in humid tropical climates)
• Brass (copper + zinc): musical instruments, door handles, decorative items (attractive gold colour, harder than copper)
• Bronze (copper + tin): statues, bells, marine propellers (harder than copper, resists seawater corrosion)
• Duralumin (aluminium + copper + magnesium + manganese): aircraft construction (lightweight yet strong)
• Solder (lead + tin): joining electrical components (low melting point)

Properties of common non-metals

Carbon exists as different allotropes:

• Diamond: extremely hard, high melting point, electrical insulator (each carbon bonded to four others in giant covalent structure)
• Graphite: soft and slippery, conducts electricity (layered structure with delocalised electrons), used in pencils and as lubricant

Sulphur: yellow solid, brittle, burns in air to form sulphur dioxide (used in vulcanising rubber, manufacturing sulphuric acid)

Nitrogen: colourless gas, unreactive, used in fertiliser production (ammonia synthesis) and food packaging

Oxygen: colourless gas, supports combustion, essential for respiration and combustion reactions

Chlorine: greenish-yellow gas, toxic, powerful oxidising agent, used in water purification throughout Caribbean water treatment plants

Worked examples

Example 1: Displacement reaction prediction

Question: A student adds samples of four metals to separate solutions of copper(II) sulphate. The metals used are iron, silver, magnesium, and gold.

(a) Predict which metals will displace copper from copper(II) sulphate solution. [2 marks]

(b) Write a balanced symbol equation for one displacement reaction that occurs. [2 marks]

(c) Describe the colour change observed when iron displaces copper. [2 marks]

Solution:

(a) Iron and magnesium will displace copper [1 mark] because they are more reactive than copper in the reactivity series [1 mark].

(b) Mg + CuSO₄ → MgSO₄ + Cu [1 mark for correct formulae, 1 mark for balancing]

(c) The blue colour of copper(II) sulphate solution fades [1 mark], and a brown/pink coating of copper metal forms on the magnesium/iron surface [1 mark].

Example 2: Metal extraction

Question: Zinc is extracted from zinc oxide by heating with carbon in a furnace.

(a) Write a word equation for this extraction. [1 mark]

(b) Write a balanced symbol equation for this reaction. [2 marks]

(c) Explain why this method cannot be used to extract aluminium from aluminium oxide. [2 marks]

Solution:

(a) zinc oxide + carbon → zinc + carbon monoxide [1 mark]

(b) 2ZnO + C → 2Zn + CO₂ [1 mark for formulae, 1 mark for balancing]

(c) Aluminium is more reactive than carbon [1 mark], so carbon cannot reduce aluminium oxide. Electrolysis must be used instead [1 mark].

Example 3: Properties and uses

Question: Copper is used for electrical wiring in homes throughout Trinidad and Tobago.

(a) State two physical properties of copper that make it suitable for this use. [2 marks]

(b) Pure copper wire is sometimes too soft. Suggest how the hardness can be improved. [1 mark]

(c) Explain why aluminium is increasingly used instead of copper for overhead power cables. [2 marks]

Solution:

(a) Excellent electrical conductor [1 mark]; ductile/can be drawn into wires [1 mark]; (also accept: does not corrode easily/resistant to corrosion)

(b) Mix copper with another metal to form an alloy/add small amounts of another metal [1 mark]

(c) Aluminium is less dense/lighter than copper [1 mark], reducing the weight on pylons/reducing cost of materials [1 mark].

Common mistakes and how to avoid them

• Mistake: Stating that all metals have high melting points. Correction: Mercury is liquid at room temperature (melting point -39°C), and sodium melts at 98°C. State "most metals have high melting points" or specify exceptions.

• Mistake: Writing that metals form acidic oxides. Correction: Metal oxides are basic or amphoteric (aluminium oxide, zinc oxide). Non-metal oxides are acidic. This distinction frequently appears in CXC CSEC Chemistry papers.

• Mistake: Claiming less reactive metals can displace more reactive metals. Correction: Only more reactive metals displace less reactive metals from their compounds. Always check the reactivity series before predicting displacement reactions.

• Mistake: Confusing reduction with oxidation in extraction. Correction: In metal extraction, reduction removes oxygen from the metal oxide. The metal ore is reduced; the carbon or carbon monoxide is oxidised. Remember: reduction is loss of oxygen or gain of electrons.

• Mistake: Assuming all metals react with dilute acids. Correction: Only metals above hydrogen in the reactivity series (up to and including zinc) react with dilute acids to produce hydrogen gas. Copper, silver, and gold do not react.

• Mistake: Stating that graphite is not a form of carbon because it conducts electricity. Correction: Graphite is an allotrope of carbon with delocalised electrons between layers, making it the only non-metal element that conducts electricity well. This unusual property appears regularly in exam questions.

Exam technique for Metals and Non-Metals

• Command word "State": requires a concise answer without explanation. When asked to state properties, give the property name only: "ductile," "conducts electricity," "lustrous." Avoid wasting time on explanations unless asked to "explain" or "give reasons."

• Command word "Explain": requires reasoning. For reactivity series questions, always reference relative positions: "Magnesium is above copper in the reactivity series, therefore magnesium will displace copper from copper sulphate solution." Expect 2 marks for complete explanations.

• Displacement reaction questions: write both the word equation AND balanced symbol equation if the question asks for an equation without specifying which type. Show the more reactive metal replacing the less reactive metal clearly. Common displacement pairs tested: zinc-copper, magnesium-iron, magnesium-copper.

• Extraction questions: identify the position in the reactivity series first, then select the extraction method. Questions may present unfamiliar ores but the principle remains the same: above carbon requires electrolysis, at or below carbon uses reduction with carbon. Expect 3-5 marks for describing extraction processes with equations.

Quick revision summary

Metals are lustrous, malleable, ductile conductors that form positive ions and basic oxides. Non-metals are dull, brittle insulators that form negative ions and acidic oxides. The reactivity series (potassium to platinum) predicts displacement reactions and determines extraction methods: reactive metals need electrolysis; moderately reactive metals are reduced by carbon; unreactive metals occur native. Alloys improve metal properties for specific applications. Metal oxides are basic; non-metal oxides are acidic. More reactive metals displace less reactive metals from their compounds.