A metal’s place in the reactivity series tells you how it is extracted from its ore. Metals above carbon need electrolysis, metals below carbon can be reduced by carbon, and the least reactive metals can occur uncombined.
This is the second lesson in metals and reactivity. It builds directly on the ranking from ordering metals using displacement.
Why does reactivity decide the method?
A reactive metal holds on to oxygen strongly. To extract it from its oxide you must remove that oxygen, and the more reactive the metal, the stronger the method has to be.
Carbon can take oxygen from a metal oxide only if carbon is the more reactive element in the pair. So the series, with carbon placed in it, sorts metals into three groups.
| Group | Examples | Usual approach |
|---|---|---|
| Above carbon | potassium, sodium, calcium, magnesium, aluminium | electrolysis of the molten compound |
| Below carbon | zinc, iron | reduction with carbon or carbon monoxide |
| Very unreactive | gold | found uncombined |
Electrolysis needs large amounts of electrical energy. That is why it is kept for the metals that cannot be reduced more cheaply. Industrial extraction is done only in controlled plants, and this lesson treats it as a reasoning topic.
How to choose a method, step by step
- Find the metal in the series and find where carbon sits.
- Is the metal above carbon? Then carbon cannot reduce its oxide, so the answer is electrolysis.
- Is it below carbon? Then reduction of the oxide with carbon, or carbon monoxide, is possible.
- Is it very far down? Then it may occur as the uncombined metal.
- Write the equation for the step and check that both sides balance.
Worked example
Name a suitable method for each of aluminium, iron and gold, and write one equation where it applies.
Aluminium: it is above carbon, so carbon cannot reduce aluminium oxide. The oxide is melted, dissolved in molten cryolite, and electrolysed. Overall: 2Al₂O₃ → 4Al + 3O₂. Check: Al 4 and 4, O 6 and 6.
Iron: it is below carbon, so carbon monoxide can reduce iron(III) oxide in the blast furnace. Fe₂O₃ + 3CO → 2Fe + 3CO₂. Check: Fe 2 and 2, C 3 and 3, O 3 + 3 = 6 and 6.
Gold: it is very unreactive and is found uncombined. It is separated from other material physically, so no reduction equation is needed.
Answer: electrolysis, carbon monoxide reduction, and separation of the native metal.
The mistake to watch for
A common slip is to choose the method by cost, without checking the series.
Mistaken answer: “Aluminium is extracted by heating with carbon, because carbon is cheap.”
The student ignored that aluminium is more reactive than carbon, so the reaction cannot happen.
The correction is to start from the position, not the price. Ask “is the metal above or below carbon?” before naming any method. Cost then explains why electrolysis is used only when nothing cheaper will work.
Check yourself
1. Zinc oxide is heated with carbon to give zinc and carbon dioxide. Write the balanced equation.
Show answer
2ZnO + C → 2Zn + CO₂. Check: Zn 2 and 2, O 2 and 2, C 1 and 1.
2. Calcium is above carbon in the series. What method is used, and why not carbon?
Show answer
Electrolysis of a molten calcium compound. Calcium is more reactive than carbon, so carbon cannot take the oxygen from calcium oxide.
3. Explain why gold is often found as the metal itself.
Show answer
Gold is very unreactive, so it does not readily combine with other elements in the ground. It stays as the uncombined metal and can be separated from rock without a chemical reduction.
Where this leads next
The next skill uses the same reactivity ideas in a different setting: explaining corrosion from supplied evidence. Electrolysis as a method is covered in more detail in electrolysis reasoning, and the metals and reactivity practice set mixes all the skills.
Students who know each method but hesitate on an unfamiliar metal often need practice making the decision, not more facts. That is what we work on in online one-to-one Chemistry tuition.