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How do we rank metals by reactivity, and how does that decide the way we extract them from their ores?

Place metals in order of reactivity from their reactions, use displacement reactions, and relate reactivity to the method used to extract a metal

A focused N(A)-Level answer on metals. The reactivity series, displacement reactions, and how a metal's reactivity decides whether it is extracted by carbon or by electrolysis.

Generated by Claude Opus 4.88 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

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  1. What this dot point is asking
  2. The answer
  3. Examples in context
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What this dot point is asking

SEAB wants you to place metals in order of reactivity from how they react, to use displacement reactions, and to link a metal's reactivity to the method used to extract it from its ore. The central idea is that the more reactive a metal is, the harder it is to separate from its compounds, so the more powerful the extraction method must be.

The answer

The reactivity series

The reactivity series is a list of metals in order of how readily they react, most reactive at the top. A common order is:

potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold.

More reactive metals react faster with water and acids; less reactive metals such as gold barely react at all, which is why gold is found as the metal itself.

Displacement reactions

A more reactive metal will displace (push out) a less reactive metal from its compound. For example, iron is more reactive than copper, so:

iron+copper(II) sulfate→iron(II) sulfate+copper\text{iron} + \text{copper(II) sulfate} \rightarrow \text{iron(II) sulfate} + \text{copper}

The iron takes the place of the copper, the blue solution fades, and a layer of copper forms. Displacement reactions are a quick way to compare the reactivity of two metals.

Extraction of metals

Most metals are found combined in compounds called ores, so they must be extracted. The method depends on the metal's reactivity:

  • metals less reactive than carbon (such as iron, zinc and lead) can be extracted by heating the ore with carbon, which displaces the metal,
  • metals more reactive than carbon (such as aluminium, magnesium and sodium) cannot be displaced by carbon, so they are extracted by electrolysis,
  • very unreactive metals (such as gold) are found uncombined and need no chemical extraction.

This is why iron was used by ancient peoples long before aluminium: iron is easy to extract with carbon, but aluminium needs electricity.

Examples in context

Example 1. Why aluminium was once more precious than gold. Before electrolysis was developed, no one could extract reactive aluminium cheaply, so it was rare and costly. Once electricity could be used to extract it, aluminium became one of the most common everyday metals.

Example 2. Protecting iron from rusting with a more reactive metal. Attaching blocks of a more reactive metal such as zinc or magnesium to a steel ship's hull protects the iron. The more reactive metal corrodes instead of the iron, an idea that comes straight from the reactivity series.

Try this

  • Cue. State what happens when zinc is added to copper(II) sulfate solution. Zinc displaces copper; the blue fades and copper forms (zinc is more reactive).
  • Cue. Name the method used to extract sodium from its ore. Electrolysis (sodium is above carbon).
  • Cue. Explain why gold is found as the metal itself. Gold is so unreactive that it does not combine to form compounds.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original4 marksAn iron nail is placed in blue copper(II) sulfate solution. (a) State what you would observe. (b) Explain the observation using the reactivity series. (c) Name this type of reaction.
Show worked answer →

(a) The blue solution fades (turns paler), and a brown or pink-brown coating of copper forms on the iron nail.

(b) Iron is more reactive than copper, so iron takes the place of copper. The iron goes into solution and the copper is pushed out as a solid.

(c) This is a displacement reaction.

What markers reward: the colour change and copper deposit, the explanation that the more reactive iron displaces the less reactive copper, and naming it a displacement reaction.

Original3 marks(a) State why very reactive metals such as aluminium are extracted by electrolysis rather than by heating with carbon. (b) Name a metal that can be extracted by heating its ore with carbon.
Show worked answer →

(a) Aluminium is more reactive than carbon, so carbon cannot displace it from its ore. Electrolysis is used instead to separate the metal.

(b) Iron (or zinc, or lead) is less reactive than carbon, so it can be extracted by heating its ore with carbon.

What markers reward: a metal more reactive than carbon needs electrolysis, and a correct metal less reactive than carbon for the carbon method.

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