Reactivity of Metals
Summary: The reactivity series orders metals by their tendency to lose electrons and form positive ions: K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Ag > Au. More reactive metals displace less reactive ones from compounds. Position in the series determines reaction with water, steam, and acids — and the extraction method needed. Tags: igcse chemistry metals reactivity-series displacement Created: 2026-07-14 Last Updated: 2026-07-26
The Reactivity Series (MEMORISE THIS)
MOST REACTIVE
K — Potassium (Please)
Na — Sodium (Send)
Ca — Calcium (Cats)
Mg — Magnesium (Monkeys)
Al — Aluminium (And)
(C) — Carbon (Clever)
Zn — Zinc (Zebras)
Fe — Iron (In)
Pb — Lead (Large)
(H) — Hydrogen (Hot)
Cu — Copper (Cages)
Ag — Silver (Securely)
Au — Gold (Guarded)
LEAST REACTIVE
Mnemonic: “Please Send Cats Monkeys And Clever Zebras In Large Hot Cages Securely Guarded”
Note: Carbon and hydrogen are non-metals but are included for reference — they are key reference points for extraction methods and acid reactions.
What Determines Reactivity?
A metal’s reactivity is its tendency to lose electrons to form positive ions:
- M → Mⁿ⁺ + ne⁻
| Factor | Effect on Reactivity |
|---|---|
| Atomic radius | Larger atom → outer electrons further from nucleus → easier to lose → MORE reactive |
| Nuclear charge | Higher charge → stronger attraction → harder to lose → LESS reactive |
| Shielding | More inner shells → less nuclear attraction on outer electrons → MORE reactive |
For Group 1 metals, the atomic radius and shielding effects dominate → reactivity INCREASES down the group.
Reactions with Water
Cold Water (Metals ABOVE Mg)
| Metal | Observation | Equation | Notes |
|---|---|---|---|
| K | Violent, ignites spontaneously with lilac flame, may explode | 2K + 2H₂O → 2KOH + H₂ | Too dangerous for school |
| Na | Vigorous, melts into ball, darts on surface, may ignite | 2Na + 2H₂O → 2NaOH + H₂ | Demonstrates at IGCSE |
| Ca | Steady reaction, bubbles of H₂, white suspension forms | Ca + 2H₂O → Ca(OH)₂ + H₂ | Ca(OH)₂ is sparingly soluble — turns water milky |
| Mg | Very slow at room temperature (thin oxide layer) | Mg + 2H₂O → Mg(OH)₂ + H₂ | Produces a few bubbles over hours |
Steam (Metals Mg → Fe)
| Metal | Observation | Equation |
|---|---|---|
| Mg | Reacts vigorously, bright white flame, white MgO powder | Mg + H₂O(g) → MgO + H₂ |
| Al | Reacts when oxide layer is broken through (powdered Al) | 2Al + 3H₂O(g) → Al₂O₃ + 3H₂ |
| Zn | Reacts when heated, yellow when hot → white when cold | Zn + H₂O(g) → ZnO + H₂ |
| Fe | Reacts slowly when heated, Fe₃O₄ formed | 3Fe + 4H₂O(g) → Fe₃O₄ + 4H₂ |
Key difference: Cold water → metal HYDROXIDE; steam → metal OXIDE.
Reactions with Dilute Acids
Only metals ABOVE hydrogen in the reactivity series react with dilute acids:
General equation: Metal + Acid → Salt + Hydrogen gas
| Metal | Reaction with dilute HCl | Reaction with dilute H₂SO₄ |
|---|---|---|
| K | EXPLOSIVE — NEVER DONE | EXPLOSIVE — NEVER DONE |
| Na | EXPLOSIVE — NEVER DONE | EXPLOSIVE — NEVER DONE |
| Ca | Reacts vigorously, CaCl₂ + H₂ | Reacts, CaSO₄ coats metal (slows reaction) |
| Mg | Reacts vigorously, lots of H₂, gets hot | Reacts vigorously, MgSO₄ + H₂ |
| Al | Reacts after oxide layer removed | Reacts after oxide layer removed |
| Zn | Reacts steadily, H₂ evolved | Reacts steadily, H₂ evolved |
| Fe | Reacts slowly, FeCl₂ (pale green) | Reacts slowly, FeSO₄ (pale green) |
| Pb | Reacts very slowly (PbCl₂ insoluble — coats metal) | Reacts very slowly (PbSO₄ insoluble — coats metal) |
| Cu, Ag, Au | NO REACTION | NO REACTION |
Test for H₂ gas: Collect in inverted test tube → apply lighted splint → squeaky pop.
Displacement Reactions
A more reactive metal displaces a less reactive metal from a solution of its salt.
General Principle
More reactive metal + Salt of less reactive metal → Salt of more reactive metal + Less reactive metal
Examples
Zinc + Copper(II) Sulfate: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
- Observation: Grey zinc becomes coated with reddish-brown copper; blue CuSO₄ solution fades to colourless ZnSO₄
- Zinc is MORE reactive than copper → displaces it
Magnesium + Iron(II) Sulfate: Mg(s) + FeSO₄(aq) → MgSO₄(aq) + Fe(s)
- Observation: Grey Mg ribbon dissolves; grey iron metal deposits; green FeSO₄ solution fades
Copper + Zinc Sulfate: Cu(s) + ZnSO₄(aq) → NO REACTION
- Copper is LESS reactive than zinc → CANNOT displace it
Thermite Reaction (Al + Fe₂O₃)
2Al(s) + Fe₂O₃(s) → Al₂O₃(s) + 2Fe(l)
- Highly exothermic — temperature reaches ~2500°C
- Molten iron produced — used to weld railway tracks
- Al is MORE reactive than Fe → reduces Fe₂O₃
Competition Reactions: Reduction with Carbon
Carbon is used as a reducing agent to extract metals from their oxides:
Metal oxide + Carbon → Metal + Carbon dioxide (or Carbon monoxide)
Carbon can ONLY reduce metal oxides of metals below it in the reactivity series:
| Metal Oxide | Reduction by Carbon? | Equation |
|---|---|---|
| K₂O, Na₂O | ❌ NO — K/Na too reactive | Must use electrolysis |
| CaO, MgO | ❌ NO | Must use electrolysis |
| Al₂O₃ | ❌ NO | Must use electrolysis |
| ZnO | ✅ YES | 2ZnO + C → 2Zn + CO₂ |
| Fe₂O₃ | ✅ YES | 2Fe₂O₃ + 3C → 4Fe + 3CO₂ |
| PbO | ✅ YES | 2PbO + C → 2Pb + CO₂ |
| CuO | ✅ YES | 2CuO + C → 2Cu + CO₂ |
The Aluminium Oxide Anomaly
Aluminium appears less reactive than expected because it is coated with a thin, tough, transparent layer of aluminium oxide (Al₂O₃) that prevents water and oxygen from reaching the metal underneath:
- In powder form (high surface area, oxide layer disrupted), Al reacts vigorously
- The oxide layer is why Al doesn’t react with water and seems unreactive in air
- Al₂O₃ is amphoteric — it reacts with BOTH acid and alkali, dissolving the oxide layer
Key Concepts from Past Papers
Definitions You MUST Know
- Reactivity series: a list of metals in order of their tendency to lose electrons and form positive ions
- Displacement reaction: a reaction where a more reactive element takes the place of a less reactive element in a compound
- Oxidation (in terms of electron transfer): loss of electrons
- Reduction (in terms of electron transfer): gain of electrons
- Reducing agent: a substance that reduces another substance and is itself oxidised
- Ore: a naturally occurring rock containing enough metal or metal compound to make extraction economically viable
Recurring Mark Scheme Answers
- “The more reactive metal donates/loses electrons more readily”
- “X displaces Y because X is more reactive / higher in the reactivity series”
- “No reaction because [less reactive metal] cannot displace [more reactive metal]”
- “Carbon reduces the metal oxide — carbon is oxidised, the metal is reduced”
- “Metals above carbon must be extracted by electrolysis because carbon cannot reduce their oxides”
- “Aluminium appears unreactive due to its protective oxide layer”
Common Mistakes
- Forgetting the reactivity series order: The mnemonic is your best friend — use it
- Saying “X displaces Y because X is above Y”: Must say “because X is MORE REACTIVE than Y”
- Confusing Mnemonic: “Please Send…” — it’s Monkeys (Mg) and And (Al), not Cats Monkeys Zebras
- Forgetting carbon’s position: Carbon sits between Al and Zn — key for extraction methods
- Thinking all metals react with water: Only K, Na, Ca react with cold water; Mg–Fe react with steam; below Fe = no reaction
- Forgetting state symbols in equations: Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
Common Question Types
Type 1: “Use the reactivity series to explain whether a reaction will occur” (2–3 marks)
- Frequency: ~45% of papers
- Approach: Compare positions in the series → predict displacement
Type 2: “Write a balanced equation for the reaction between X and Y” (2–3 marks)
- Frequency: ~40% of papers
- Most tested: acid reactions, displacement, carbon reduction
Type 3: “Describe an experiment to determine the order of reactivity” (4–6 marks)
- Frequency: ~25% of papers
- Approach: (1) Measure temperature change with same acid, (2) Measure rate of H₂ evolution, (3) Use displacement reactions systematically
Type 4: “Deduce the order of reactivity from given experimental results” (2–3 marks)
- Frequency: ~30% of papers
- Method: If X displaces Y → X is above Y. Build a sequence.
Key Facts to Memorize
- Reactivity series: K > Na > Ca > Mg > Al > (C) > Zn > Fe > Pb > (H) > Cu > Ag > Au
- Cold water: Only K, Na, Ca react (Mg = very slow)
- Steam: Mg, Al, Zn, Fe react (must be heated)
- Dilute acid: All metals above H react; Cu, Ag, Au = NO reaction
- Displacement: More reactive displaces less reactive from its salt solution
- Carbon reduction: Only for metals BELOW carbon in the series (Zn, Fe, Pb, Cu)
- Electrolysis: Required for metals ABOVE carbon (K, Na, Ca, Mg, Al)
- Al₂O₃ is protective — makes Al seem less reactive than it really is
- Thermite: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe (highly exothermic)
- The more reactive the metal, the more stable its compounds → harder to extract
Related Notes
- Metal Extraction — How metals are extracted based on their reactivity
- Redox Reactions — Oxidation and reduction in metal reactions
- Rusting of Iron — Corrosion and reactivity in action
- Uses of Metals — How reactivity influences which metals we use
- Electrolysis — Extraction of Al and other reactive metals
- Displacement Reaction — Detailed displacement chemistry
- Group 1 Alkali Metals — The most reactive metals
- IGCSE-Chem-Index
Past Paper Sources
- 0620/42 M/J 2023 Q3: Determine reactivity order from displacement reactions (5 marks)
- 0971/32 O/N 2022 Q5: Write equations for reactions with water, steam, and acid (6 marks)
- 0620/43 M/J 2020 Q7(a): Explain why carbon can reduce Fe₂O₃ but not Al₂O₃ (3 marks)
- 0620/62 M/J 2019 Q5: Describe experiment to compare reactivity of three metals (5 marks)
- 0971/52 O/N 2023 Q4: Displacement — observations and ionic equations (4 marks)
- 0620/32 O/N 2018 Q7(c): Thermite reaction — explain and write equation (3 marks)
IGCSE Chemistry (0620/0971) wiki. The reactivity series is the foundation of metal chemistry — it governs extraction, reactions, corrosion, and displacement.