The reactivity series
Order of reactivity, reactions with water and acid, and displacement reactions.
Review these first
Learning objectives
What you need to be able to do
Teacher-mapped phrasing — check against the official Cambridge syllabus for exact wording.
- 9.4.1Place metals in order of reactivity using their reactions with water, steam and dilute acid.
- 9.4.2Explain displacement reactions of metals in terms of relative reactivity and electron transfer.Supplement
8 minute read
The reactivity series
The reactivity series ranks metals from most to least reactive:
Potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold
Carbon and hydrogen are included, though not metals, as useful reference points for extraction methods and for predicting reactions with acid.
Placing metals using their reactions
- Reaction with cold water: the most reactive metals (potassium, sodium, calcium) react readily with cold water, producing a metal hydroxide and hydrogen gas. Potassium and sodium react vigorously enough to be dangerous; calcium reacts more gently.
- Reaction with steam: less reactive metals (like magnesium, zinc, iron) may not react with cold water but will react with steam, producing a metal oxide and hydrogen.
- Reaction with dilute acid: metals above hydrogen in the series react with dilute acids to produce a salt and hydrogen gas — and the more reactive the metal, the more vigorous the reaction (more rapid fizzing). Metals below hydrogen (copper, silver, gold) do not react with dilute acids at all.
Displacement reactions
A more reactive metal will displace a less reactive metal from a solution of its salt, because the more reactive metal more readily loses electrons to form ions.
Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
In terms of electrons: zinc atoms lose electrons (are oxidised) to form Zn²⁺ ions, while Cu²⁺ ions gain those electrons (are reduced) to form copper atoms. The reactive metal "wins" the electron transfer because it holds onto its own electrons less strongly.
Think of it like this
The reactivity series is like a queue where whoever is more "eager to let go" of their electrons (more reactive) will always push in and take the place of someone less eager, in any encounter between a metal and another metal's ions — reactivity is really just a ranking of how readily each metal gives up its electrons.
Common misconceptions
- Assuming a less reactive metal can displace a more reactive one. Displacement always goes in one direction: more reactive displaces less reactive, never the reverse.
- Forgetting that carbon and hydrogen, though not metals, are placed in the series as useful benchmarks — carbon for extraction methods, hydrogen for predicting reactions with dilute acid.
- Believing every metal reacts with water in some way. Metals below a certain point in the series (like copper, silver, gold) do not react with water or steam at all under normal conditions.
In the exam
- When explaining a displacement reaction, describe it in terms of electron transfer for full marks at supplement level — state clearly which metal loses electrons and which gains them.
- A common practical question describes observations from adding several metals to acid and asks you to rank them — use the rate of bubbling (fizzing) as your evidence, more vigorous meaning more reactive.