Reactivity Series
Edexcel International GCSE ChemistryΒ· 2.15β2.21Β· 25 min read
1. Reactivity Series Order & Ranking from Water/Acid Reactionsβ β ββββ± 5 min
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Reactivity Series
A ranked list of metals ordered from highest reactivity (top) to lowest reactivity (bottom), determined by their tendency to form positive ions.
The Edexcel IGCSE required reactivity order is: Potassium (K) > Sodium (Na) > Lithium (Li) > Calcium (Ca) > Magnesium (Mg) > Aluminium (Al) > Zinc (Zn) > Iron (Fe) > Copper (Cu) > Silver (Ag) > Gold (Au). You can rank metals by observing their reaction with cold water, steam, and dilute hydrochloric/sulfuric acid: the more vigorous the reaction, the higher the reactivity. Metals above hydrogen react with dilute acids to produce salt and hydrogen gas; metals below hydrogen do not react with dilute acids.
A student adds equal sized, equal surface area pieces of metals W, X, Y to equal volumes of 1mol/dmΒ³ dilute hydrochloric acid. W fizzes very slowly, X fizzes violently, Y has no visible change. Order the metals from most to least reactive, and identify which could be copper.
- 1
Faster fizzing = higher reactivity, so the order is X > W > Y.
- 2
Copper is below hydrogen in the reactivity series, so it does not react with dilute acid. Therefore Y is copper.
2. Displacement Reactions & Reactivity Rankingβ β β βββ± 6 min
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Displacement Reaction
A reaction where a more reactive metal displaces a less reactive metal from its solid metal oxide or aqueous metal salt solution.
Displacement only occurs if the added free metal is higher in the reactivity series than the metal ion in the oxide or salt. You can use observed displacement reactions to confirm the relative reactivity of two metals. Always include state symbols in balanced equations for displacement reactions, as marks are frequently awarded for correct state symbols.
Write the balanced equation (with state symbols) for the reaction between zinc metal and copper(II) oxide when heated, and explain why the reaction occurs.
- 1
Check reactivity: Zinc is above copper in the reactivity series, so displacement occurs.
- 2
Products are zinc oxide and copper metal.
- 3
- 4
Explanation: Zinc is more reactive than copper, so it displaces copper from its oxide.
3. Redox Reactions & Key Definitionsβ β β βββ± 5 min
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Redox Reaction
A reaction where oxidation and reduction take place at the same time.
There are two accepted definitions for oxidation and reduction for this course:
1. Oxygen transfer: Oxidation = gain of oxygen; Reduction = loss of oxygen
2. Electron transfer: Oxidation = loss of electrons; Reduction = gain of electrons. The reducing agent is the substance that is oxidised, and the oxidising agent is the substance that is reduced.
Identify the oxidising and reducing agent in the reaction:
- 1
Track electron transfer: Mg loses 2 electrons to form , so Mg is oxidised, therefore it is the reducing agent.
- 2
gains 2 electrons to form Cu, so (from ) is reduced, therefore is the oxidising agent.
4. Rusting of Iron & Prevention Methodsβ β ββββ± 4 min
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Rusting
The corrosion of iron to form hydrated iron(III) oxide (rust), which requires both oxygen (from air) and water to occur.
Rusting can be prevented by removing one or both required conditions:
1. Barrier methods: Paint, oil, grease, or plastic coating blocks oxygen and water from touching the iron surface.
2. Galvanising: Coating iron with zinc, which acts as a barrier, and if scratched, zinc is more reactive than iron so it corrodes preferentially.
3. Sacrificial protection: Attaching a more reactive metal (e.g. magnesium, zinc) to iron, which oxidises instead of the iron, even when the iron is exposed to water and oxygen.
Explain why painting an iron gate prevents it from rusting.
- 1
Paint forms a waterproof, airtight barrier between the iron surface and oxygen and water in the environment.
- 2
Since both oxygen and water are required for rusting, removing their access to iron stops rust formation.
5. Required Practical: Metal Reactions with Dilute Acidsβ β β βββ± 5 min
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This practical (spec point 2.21) investigates the relative reactivity of magnesium, zinc, and iron using their reaction with dilute hydrochloric or sulfuric acid. You must use equal volumes of the same concentration acid, and equal mass, equal surface area pieces of each metal to ensure valid results. You can measure reactivity by observing the rate of fizzing, or measuring the volume of hydrogen gas produced per minute.
State the expected results of this practical, and explain what they show about the relative reactivity of the three metals.
- 1
Expected results: Magnesium fizzes fastest, then zinc, then iron fizzes slowest.
- 2
Faster reaction rate = higher reactivity, so the order is Magnesium > Zinc > Iron, matching the standard reactivity series.
6. Common Pitfalls
Wrong move:
Using the order Li > Na > K instead of the Edexcel-specified K > Na > Li
Why:
Edexcel explicitly requires the K > Na > Li order, so you will lose marks for incorrect ranking.
Correct move:
Memorise the exact spec reactivity order: K, Na, Li, Ca, Mg, Al, Zn, Fe, Cu, Ag, Au.
Wrong move:
Predicting displacement when the added metal is less reactive than the metal in the salt/oxide
Why:
Displacement only occurs if the added metal is higher in the reactivity series than the metal ion present.
Correct move:
Always check the reactivity order before predicting displacement reactions.
Wrong move:
Stating rusting only requires water or only requires oxygen
Why:
Both water and oxygen are essential for rusting to occur, as rust is hydrated iron(III) oxide.
Correct move:
Recall that both and must be present for iron to rust; removing either stops rusting.
Wrong move:
Confusing oxidising and reducing agents: stating the oxidising agent is oxidised
Why:
Oxidising agents cause oxidation in other substances, so they are themselves reduced.
Correct move:
Remember: reducing agent = oxidised; oxidising agent = reduced.
Wrong move:
Forgetting state symbols in displacement reaction equations
Why:
Edexcel exam questions often explicitly award marks for correct state symbols.
Correct move:
Always include (s), (l), (g), (aq) for all reactants and products in balanced equations.
Wrong move:
Thinking galvanising only works as a barrier method
Why:
If the zinc coating is scratched, zinc is more reactive than iron so it acts as a sacrificial metal, continuing to protect the iron.
Correct move:
Remember galvanising provides both barrier and sacrificial protection.
7. Quick Reference Cheatsheet
Metal | Reacts with cold water? | Reacts with dilute acid? | Displaces Cu from ? |
|---|---|---|---|
Potassium (K) | Yes (explosive) | Yes (explosive) | Yes |
Sodium (Na) | Yes (very vigorous) | Yes (very vigorous) | Yes |
Lithium (Li) | Yes (vigorous) | Yes (vigorous) | Yes |
Calcium (Ca) | Yes (steady) | Yes (fast) | Yes |
Magnesium (Mg) | Very slowly | Yes (fast fizzing) | Yes |
Aluminium (Al) | No | Yes (slow initially) | Yes |
Zinc (Zn) | No | Yes (steady fizzing) | Yes |
Iron (Fe) | No | Yes (slow fizzing) | Yes |
Copper (Cu) | No | No | No |
Silver (Ag) | No | No | No |
Gold (Au) | No | No | No |
8. Frequently Asked
Do I have to memorise the reactivity series order for the exam?
Yes, you must recall the exact Edexcel-specified order: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold. No reactivity data is provided in the exam Periodic Table.
What's the difference between galvanising and sacrificial protection?
Galvanising coats iron with zinc, which acts both as a barrier to water/oxygen and as a sacrificial metal if the coating is scratched. Sacrificial protection uses a more reactive metal attached directly to iron, which corrodes instead of iron even if no full barrier is present.
Going deeper
What's Next
Now that you have mastered the reactivity series, you can move on to related core topics that build directly on this knowledge. The next sub-topic is metal extraction, which uses the reactivity series to determine the correct method for extracting different metals from their ores. You will also apply the redox rules you learned here to electrolysis reactions, where oxidation and reduction occur at electrodes. Practicing past paper questions on reactivity ranking, displacement reactions, and rust prevention will help you solidify your understanding and avoid common exam mistakes.