The Reactivity Series

What this lesson covers in the specification

Incandio is aligned to this specification. It is not published by, endorsed by or affiliated with Pearson, and it reproduces none of Pearson's wording — the statement numbers are given so you can check every lesson against your own copy.

• 2.15 — Arranging metals in a reactivity series from their reactions with water and dilute acid
• 2.16 — Arranging metals in a reactivity series from displacement reactions
• 2.17 — The order of reactivity of the eleven metals named by the specification

Specification section 2(d) Reactivity series — also taught in The Gases in the Air, Combustion and Carbonates, Rusting and its Prevention, Redox.

1 · Understand it

No exam language yet. The only question this section answers is: do I actually understand what is happening?

Metals differ enormously in how readily they react. Potassium sets water alight; gold can sit in the ground for thousands of years and come out unchanged. The REACTIVITY SERIES is those metals placed in order, and the point of it is that the order is the SAME whichever reaction you use to establish it.

That consistency is what makes it a real chemical fact rather than a filing convenience. Rank the metals by their reaction with water, then rank them again by their reaction with dilute acid, then again by displacement, and the same order comes out three times. A property that shows up identically in three unrelated tests is telling you something about the metals themselves.

Statement 2.15 — building the order from water and acid

1. WITH COLD WATER: potassium, sodium, lithium and calcium react, fizzing and giving off hydrogen. Everything below them does not.
2. WITH STEAM: magnesium, zinc and iron react, although they do nothing much with cold water — so they sit below calcium and above the rest.
3. WITH DILUTE ACID: magnesium, zinc and iron fizz readily; copper, silver and gold do not react at all.
4. The speed of fizzing with acid orders the middle of the series: magnesium fastest, then zinc, then iron.
5. A metal that does not react with dilute acid is BELOW HYDROGEN in the series, and that is the dividing line the acid test establishes.

Think of it like ranking players by who beats whom

You cannot measure how good a chess player is directly. What you can do is have them play each other, and the results settle an order — if A beats B and B beats C, you expect A to beat C, and if that holds across every pairing you have a genuine ranking rather than a list of results. The reactivity series is built exactly this way. No instrument measures 'reactivity'; what you have is a great many pairwise contests — this metal displaces that one, this one reacts with acid and that one does not — and the fact that they all agree is what makes the ranking real.

Statement 2.16 is the pairwise contest itself. A MORE REACTIVE METAL DISPLACES A LESS REACTIVE ONE from a solution of its salt. Put an iron nail into blue copper(II) sulfate solution and the nail becomes coated with pink-brown copper while the blue colour fades, because iron is above copper. Put a copper strip into iron(II) sulfate solution and nothing whatever happens.

The equation is iron + copper(II) sulfate → iron(II) sulfate + copper, or Fe + CuSO₄ → FeSO₄ + Cu. The blue of the solution fades as the copper leaves it and pink-brown copper coats the nail, all because iron sits above copper.

'Nothing whatever happens' is the other half of the evidence and is easy to undervalue. A set of displacement results in which everything reacted with everything would establish no order at all. It is the reactions that FAIL that fix the direction, and in an exam a 'no reaction' answer is worth exactly as much as a colour change.

Deducing an order from a results table

Metal X displaces copper from copper sulfate but not zinc from zinc sulfate. Metal Y displaces both copper and zinc. Metal Z displaces neither, and does not react with dilute acid. Place W = zinc, X, Y and Z in order of reactivity, most reactive first.

1. Y displaces zinc, so Y is above zinc.
2. X displaces copper but NOT zinc, so X is below zinc and above copper.
3. Z displaces neither and does not react with dilute acid, so Z is below hydrogen and is the least reactive of the four.
4. Putting these together: Y, then zinc, then X, then Z.
5. Note that Z's failure to react with acid did not just confirm its position — it is the only evidence placing it below hydrogen rather than merely below copper.

Answer: Y > zinc > X > Z, with Z below hydrogen on the acid evidence.

Statement 2.17 asks for eleven metals in order, and it is worth learning as a list because almost every question in this part of the specification depends on it. In order of decreasing reactivity: POTASSIUM, SODIUM, LITHIUM, CALCIUM, MAGNESIUM, ALUMINIUM, ZINC, IRON, COPPER, SILVER, GOLD. HYDROGEN and CARBON are placed in the series too, although they are not metals, because their positions decide which acids a metal will attack and which metals can be extracted with carbon.

Aluminium is worth a note, because it appears high in the series and yet seems unreactive in everyday life — aluminium window frames do not corrode away. The reason is that aluminium reacts so readily with oxygen that a thin, tough, unreactive layer of aluminium oxide forms on any exposed surface immediately and then protects the metal beneath. The metal is as reactive as its position says; you are simply never seeing bare aluminium.

2 · Grade 9 Notes

A different job from the section above. You have already understood it; this is the precise set of things to LEARN — definitions to reproduce word for word, processes in order, equations with units, and the answers that score full marks.

Statement 2.17 — the series, most reactive first

• POTASSIUM · SODIUM · LITHIUM · CALCIUM · MAGNESIUM · ALUMINIUM · (CARBON) · ZINC · IRON · (HYDROGEN) · COPPER · SILVER · GOLD
• CARBON and HYDROGEN are not metals but are placed in the series because their positions are what matter
• Above HYDROGEN → reacts with dilute acid. Below hydrogen → does not
• Below CARBON → can be extracted from its ore by reduction with carbon. Above carbon → needs electrolysis
• ALUMINIUM behaves as though unreactive because a tough oxide layer forms instantly and protects it

Statement 2.15 — what reacts with what

The vocabulary of this page

Reactivity series

A list of metals in order of how readily they react, established by reactions with water, acid and by displacement.

Displacement

A reaction in which a more reactive metal takes the place of a less reactive one in a solution of its salt.

Native metal

A metal found uncombined in the ground because it is too unreactive to have formed compounds — gold and silver.

Statement 2.16 — placing a metal by displacement

1. Add the metal to a solution of the salt of a second metal.
2. If a reaction occurs — a colour change, or a coating on the metal — the added metal is MORE reactive than the one in solution.
3. If NOTHING happens, the added metal is LESS reactive, and this is just as informative.
4. Repeat with several pairs so that each metal is tested against the others.
5. Arrange the metals so that every result is consistent; the order that satisfies them all is the reactivity series.

Model answer [4 marks]

Describe what is seen when an iron nail is placed in blue copper(II) sulfate solution, and explain why. [4]

The iron nail becomes coated with a pink-brown solid, which is copper, and the blue colour of the solution fades and turns pale green. Iron is more reactive than copper, so it displaces copper from the copper(II) sulfate solution. The copper is deposited on the nail and the iron goes into solution as iron(II) sulfate, which is pale green. The equation is Fe + CuSO₄ → FeSO₄ + Cu.

Model answer [3 marks]

A metal does not react with dilute hydrochloric acid. What does this tell you about its position in the reactivity series, and name two metals it could be. [3]

A metal that does not react with dilute acid is positioned below hydrogen in the reactivity series, because only metals above hydrogen are reactive enough to displace it from an acid. The metal could be copper, silver or gold, all of which are below hydrogen and do not react with dilute acids.

Not this: Aluminium is low in the reactivity series, because it does not corrode.

This: Aluminium is HIGH in the series, above zinc and iron. It appears unreactive only because it reacts with oxygen so readily that a tough oxide layer forms instantly and seals the surface — you never see bare aluminium.

Mark-losing trap. 'No reaction' is REAL EVIDENCE. It is what fixes the direction of the series, so write it.

Mark-losing trap. Above HYDROGEN reacts with dilute acid; below it does not. That line is what the acid test finds.

Mark-losing trap. Learn the eleven in order — almost every question in this part of the topic needs them.

3 · Prove it — the five questions

The five questions climb Grade 6 → Grade 7 → Grade 8 → Grade 9 → Grade 9 challenge, and are marked inside Incandio on your own device, by rule, with an authored diagnosis of the mistake you actually made. The mark schemes stay in the app so that the practice is worth doing; the questions themselves are here.

1. Grade 6 · State [1 mark] — Which of these metals is the most reactive?
2. Grade 7 · Predict [2 marks] — A strip of copper is placed in zinc sulfate solution. What happens?
3. Grade 8 · Deduce [3 marks] — Metal P displaces copper from copper sulfate but does not react with dilute hydrochloric acid. Where does P sit relative to copper and to hydrogen?
4. Grade 9 · Describe [6 marks] — Select every statement that belongs in a full-mark description of how displacement reactions can be used to place four metals in order of reactivity.
5. 9+ · Analyse [6 marks] — A student notes that aluminium is above zinc in the reactivity series, but observes that an aluminium window frame survives outdoors for decades while a piece of zinc corrodes visibly. They conclude the series has aluminium in the wrong place. Select every statement that belongs in a full-mark analysis.

The people behind this science

Two ways into the same idea — the one whose new metals had to go at the very top, and the one who found the deeper order this series only hints at. Inside Incandio each of them answers knowing exactly which lesson you have just finished.

Humphry Davy — the one whose new metals had to go at the very top

The top of this series is Davy's work. Potassium and sodium had to be placed above every metal then known, because they did to water what nothing else would, and the reason he could isolate them at all is that they sit so high — no chemical reagent could displace them, so electricity was the only route. He is the right person to ask what it is like to add new entries at the extreme end of a scale, and why the metals hardest to extract turned out to be the most violently reactive once you had them.

• “Where did the new metals belong among the ones already known?”
• “Why could no chemical reagent free potassium from its compound?”
• “What did the new metals do that no other metal would?”
• “Is a metal that is hard to extract always a reactive one?”
• “Which reaction surprised you most?”

Dmitri Mendeleev — the one who found the deeper order this series only hints at

The reactivity series is an ordering built purely from observation — it records what happens without saying why, and a learner is entitled to ask whether that counts as understanding. Mendeleev faced the same question about his own table, which arranged the elements by a pattern he could not account for. He is worth asking about the difference between an order that merely summarises experiments and one that predicts them, and about how much confidence a pattern deserves before its explanation is known.

• “Is an order built from experiments an explanation of anything?”
• “How did you know your table was more than a filing system?”
• “Why do the reactive metals cluster where they do in your table?”
• “What made you trust a pattern you could not explain?”
• “How would you have tested whether a series like this was real?”

Carry on through the course

• Previous lesson: Combustion and Carbonates
• Next lesson: Rusting and its Prevention
• Group 1 — the Alkali Metals — Metals soft enough to cut with a knife, which set fire to water — and get worse as you go down.
• Group 7 — the Halogens — A green gas, a brown liquid and a grey solid — and a trend that runs the opposite way to Group 1.
• The Gases in the Air — Four gases, one of which is doing almost all the chemistry — and how to measure it without ever touching it.
• Combustion and Carbonates — Three things burning in oxygen, one carbonate breaking apart, and the 0.04% gas that changes the climate.
• Rusting and its Prevention — Two things are needed to rust iron, and every method of stopping it removes one of them — or cheats.
• All of Chemistry · Chemistry key terms · required practicals · equations · Incandio Science · The 4CH1 specification