Overview
What you’ll learn
- Describe metallic bonding and use it to explain the electrical and thermal conductivity, malleability and high melting points of metals.
- State the order of the reactivity series (K, Na, Ca, Mg, Al, Zn, Fe, Pb, H, Cu, Ag, Au) and describe how it is established from reactions with water, steam, dilute acids and displacement.
- Write equations for the reactions of metals with cold water, steam and dilute acids, and explain why metals below hydrogen do not react with acids.
- Describe the extraction of iron in the blast furnace (raw materials, coke, hot air, limestone) with the equations for each step, and explain why aluminium must be extracted by electrolysis.
- Discuss the social, economic and environmental advantages and difficulties of recycling metals.
In 30 seconds
- 1Metallic bonding: positive ions in a sea of delocalised electrons — explains conduction of heat and electricity and malleability (layers slide without breaking bonding).
- 2Reactivity series: K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Ag > Au — carbon and hydrogen slot in as reference points.
- 3Cold water reacts with K, Na, Ca (hydroxide + H₂); steam reaches Mg to Fe (oxide + H₂); dilute acids attack everything above hydrogen, not Cu/Ag/Au.
- 4Displacement orders metals: a more reactive metal displaces a less reactive one from its salt (Fe + CuSO₄ → FeSO₄ + Cu).
- 5Extraction method follows reactivity: electrolysis for K–Al, heating with carbon/coke for Z–Cu, found native for Ag–Au.
- 6Blast furnace: coke burns (C + O₂ → CO₂), more coke reduces it (CO₂ + C → 2CO), and Fe₂O₃ + 3CO → 2Fe + 3CO₂; limestone removes sandy impurity as slag (CaSiO₃).
- 7Aluminium is extracted by electrolysis of molten aluminium oxide in molten cryolite — too reactive for carbon reduction; Al³⁺ + 3e⁻ → Al at the cathode.
- 8Recycling metals saves resources, energy and landfill (recycling aluminium uses ~5% of the energy of extraction) but needs sorting and collection systems.
Notes · 1 of 5
Metallic bonding and metal properties
Ions in a sea of electrons — the model that explains every metal property at once.
In a metal, each atom surrenders its outer electrons to a shared sea of delocalised electrons, leaving positive ions arranged in regular layers. The attraction between the positive ions and the negative electron sea is the metallic bond.
The model pays for itself immediately: the free electrons drift when a voltage is applied (electrical conduction) and carry kinetic energy along the bar (heat conduction); the layers of ions can slide over each other without shattering the bonding (malleability — metals can be hammered into shape); and the strong attraction needs lots of energy to overcome (high melting points, except the alkali metals).
Notes · 2 of 5
The reactivity series
One ladder that predicts water reactions, acid reactions and displacement at a glance.
The reactivity series ranks metals by how easily they lose electrons: K, Na, Ca, Mg, Al, (C), Zn, Fe, Pb, (H), Cu, Ag, Au. Carbon and hydrogen are not metals but act as reference lines: metals above carbon are too reactive to extract with coke; metals above hydrogen fizz in dilute acids.
| Region | Cold water | Steam | Dilute acids | Extraction |
|---|---|---|---|---|
| K, Na, Ca | Violent — hydroxide + H₂ | — (too violent) | Dangerously violent | Electrolysis |
| Mg, Al, Zn, Fe | Slow or none (Al passivated) | React — oxide + H₂ | React — salt + H₂ | Electrolysis (Al) or coke (Zn, Fe) |
| Pb, (H) | No | No (Pb slow) | Very slow (Pb) | Coke reduction |
| Cu, Ag, Au | No | No | No reaction | Found native / easy reduction |
Notes · 3 of 5
Reactions with water, steam and acids
Same electron-losing story, three levels of aggression.
Cold water: the top of the series reacts briskly — 2Na + 2H₂O → 2NaOH + H₂, Ca + 2H₂O → Ca(OH)₂ + H₂. Magnesium barely manages cold water but obeys steam: Mg + H₂O(g) → MgO + H₂. Iron glows through steam only slowly: 3Fe + 4H₂O(g) → Fe₃O₄ + 4H₂.
Dilute acids: everything above hydrogen forms a salt plus hydrogen — Mg + 2HCl → MgCl₂ + H₂, Zn + H₂SO₄ → ZnSO₄ + H₂. Below hydrogen nothing happens: copper is what makes water pipes and gold what makes jewellery safe from acids. (Aluminium reacts on paper but its oxide coat passivates it, which is why foil survives vinegar.)
Notes · 4 of 5
Extracting metals: the blast furnace and electrolysis
Reactivity decides the method — coke for the middle, electricity for the top.
Metals above carbon are locked into their ores too tightly for coke — they need electrolysis (expensive electricity, but the only way). The middle of the ladder (zinc to copper) is won by reduction with carbon monoxide. Gold and silver occur native (uncombined) because they barely react at all.
The blast furnace (iron ore haematite, coke, limestone, hot air): coke burns giving heat — C + O₂ → CO₂; more coke converts it to the true reducing agent — CO₂ + C → 2CO; then the payload — Fe₂O₃ + 3CO → 2Fe + 3CO₂. Limestone decomposes (CaCO₃ → CaO + CO₂) and the basic calcium oxide mops up sandy silica: CaO + SiO₂ → CaSiO₃ — molten slag, which floats on the iron and is drained off separately.
Aluminium sits above carbon, so it is pulled out by electrolysis of molten aluminium oxide, dissolved in molten cryolite to slash the melting point from 2072 °C to about 950 °C. At the cathode: Al³⁺ + 3e⁻ → Al; at the anode oxygen forms, burning away the carbon anodes, which must be replaced regularly.
Notes · 5 of 5
Recycling metals
Ores run out, energy is expensive — melting old cans beats mining new ones.
Recycling a metal means collecting used articles, sorting them by type, and re-melting them into new stock. The case is three-fold: finite ore reserves are conserved; energy is saved (recycling aluminium needs only about 5% of the energy of extracting it from bauxite by electrolysis); and landfill and mining damage are reduced.
The difficulties: collecting and sorting mixed metals is labour- and cost-intensive; different alloys contaminate each other; and transport must be organised so the savings are not swallowed. Iron is easy — magnets sort it; separating aluminium from steel in household waste needs eddy-current systems or careful source separation.
Revise
Key terms
The words examiners expect you to use precisely.
- Metallic bonding
- The attraction between positive metal ions and a sea of delocalised electrons.
- Delocalised electrons
- Electrons free to move through the whole metal lattice — carriers of charge and heat.
- Malleable
- Able to be hammered into shape: metal layers slide without breaking the metallic bond.
- Reactivity series
- Metals ranked by ease of losing electrons: K, Na, Ca, Mg, Al, (C), Zn, Fe, Pb, (H), Cu, Ag, Au.
- Displacement (metals)
- A more reactive metal pushes a less reactive metal out of its salt solution.
- Ore
- A rock containing a metal compound from which the metal is worth extracting.
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- Blast furnace
- The tower furnace that reduces iron ore to iron using coke, hot air and limestone.
- Slag
- Calcium silicate waste formed when CaO from limestone mops up sandy silica in the furnace.
- Cryolite
- Molten solvent that dissolves aluminium oxide and lowers the electrolysis temperature.
- Passivation
- The protective oxide coat on aluminium that hides its true reactivity.
- Native metal
- A metal found uncombined (Au, Ag) because it is too unreactive to form ores.
- Recycling (metals)
- Collecting, sorting and re-melting used metals to save ores, energy and landfill space.
Revise
Common mistakes
Where students most often lose marks in this chapter — and what to do instead.
Mistake: Saying metals conduct because their ions move.
The ions sit in fixed layers; it is the electrons that travel.
Instead: Delocalised electrons carry charge (and heat) through the lattice.
Mistake: Mixing up the order of iron and zinc, or copper and silver.
The ladder must be memorised in order.
Instead: …Al, Zn, Fe, Pb, (H), Cu, Ag, Au — zinc above iron, silver below copper.
Show 10 more mistakesShow fewer mistakes
Mistake: Writing Mg + H₂O → MgOH + H₂.
Magnesium hydroxide needs two hydroxides; with steam the product is the oxide anyway.
Instead: Steam: Mg + H₂O(g) → MgO + H₂; cold water (Ca, Na, K): hydroxide + H₂.
Mistake: Adding copper to dilute hydrochloric acid and expecting hydrogen.
Copper sits below hydrogen.
Instead: Only metals above hydrogen displace it from acids; Cu, Ag, Au are safe.
Mistake: Extracting aluminium by heating with carbon.
Aluminium is more reactive than carbon — coke cannot reduce it.
Instead: Aluminium needs electrolysis of molten Al₂O₃ in cryolite.
Mistake: Forgetting the limestone in the blast furnace.
Without it, sandy impurity stays in the iron.
Instead: CaCO₃ → CaO + CO₂; CaO + SiO₂ → CaSiO₃ (slag).
Mistake: Naming CO₂ as the main reducing agent in the furnace.
Carbon monoxide does the reducing; CO₂ only starts the chain.
Instead: C + O₂ → CO₂ (fuel), then CO₂ + C → 2CO; the CO reduces Fe₂O₃.
Mistake: Saying cryolite lowers the melting point of aluminium metal.
It dissolves the ORE, not the metal.
Instead: Molten cryolite dissolves Al₂O₃, cutting the operating temperature and the electricity bill.
Mistake: Expecting iron to displace magnesium from magnesium sulfate.
Iron is below magnesium.
Instead: Displacement runs downhill only: Mg displaces Fe, never the reverse.
Mistake: Explaining malleability as "weak bonds break".
The bonding survives the sliding.
Instead: Layers of ions slide over each other while the electron sea keeps bonding — no fracture.
Mistake: Claiming recycling metals has no drawbacks.
Collection, sorting and transport cost money and energy.
Instead: Weigh savings against sorting costs and contamination of mixed alloys.
Mistake: Writing H₂O instead of H₂O(g) in steam equations.
State symbols mark the difference between cold water and steam chemistry.
Instead: Mg + H₂O(g) → MgO + H₂ — steam as gas, product as oxide.
Check yourself
Quick quiz
20 questions with instant explanations. About 5 minutes.
Question 1 of 3
- Question 1: current question
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- Question 3: not answered
Describe metallic bonding
In metallic bonding, the particles attracted to the delocalised electrons are
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Practise
Topical questions
Exam-style practice in three tiers, from recall to data questions.
- 4Foundation
- 5Standard
- 3Challenging
12 questions worth 46 marks, each with a model answer, mark scheme and examiner tips.
Practise topical questionsExam practice
Practice paper
A 30-mark paper set out like a school paper, with a separate mark scheme. Give yourself 40 min.
Question paper
Chapter 7 Practice Paper
30 marks · 40 min · 4 pages
5 multiple-choice questions and structured questions with answer lines. Chapter 7 (metallic bonding, reactivity series, metal reactions, extraction, recycling).
Mark scheme
PROChapter 7 Practice Paper — mark scheme
Answers · Marking points · 3 pages
Model answers with a mark for each creditworthy point — for marking at home or in class.
Where this chapter is tested
Each school sets its own scope — check your assessment outline.
Questions
Frequently asked questions
What does Sec 4 Chemistry Chapter 7 cover?
It covers section 6 of O-Level Pure Chemistry 6092: metallic bonding and metal properties, the reactivity series and how experiments build it, reactions with water/steam/acids, extraction of iron in the blast furnace and aluminium by electrolysis, and metal recycling.
How do I quickly place a metal in the reactivity series?
Test its aggression: fizzes in cold water = top group (K, Na, Ca); needs steam = middle (Mg–Fe); does nothing with acids = below hydrogen (Cu, Ag, Au); displaces copper from blue copper(II) sulfate = above copper.
Why is aluminium so hard to extract but so safe in saucepans?
Extraction must rip a strong bond to oxygen — above carbon, so electrolysis is the only way. In use, a self-repairing oxide coat passivates the surface, hiding the reactivity.
What are the four key blast furnace equations?
C + O₂ → CO₂ (fuel); CO₂ + C → 2CO (reducing agent); Fe₂O₃ + 3CO → 2Fe + 3CO₂ (reduction); CaO + SiO₂ → CaSiO₃ (slag from the limestone).
When is this chapter usually tested in school?
Metals and extraction are prelim and O-Level favourites — usually a blast furnace equation chain plus a reactivity-series deduction. Scope varies by school, so check your school’s assessment outline.
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Chapter 8: Maintaining Air Quality