Metal Oxides and the Reactivity Series — AQA GCSE Chemistry

SPEC 4.4.1.1 – 4.4.1.2 • MODULE 4

Metal Oxides & the Reactivity Series

The master list that drives all of Module 4. Metal + oxygen reactions, redox by oxygen, the reactivity series, and the four examiner traps that cost most students marks.

Why This Lesson Matters

The reactivity series is the most-cited list in GCSE Chemistry. Get it right and you'll handle metal extraction, acid reactions, displacement, and electrolysis on autopilot.

12

Metals to Memorise

2

Threshold Lines (C, H)

4

Examiner Traps Today

The Plan

Metals + oxygen → metal oxides. Oxidation/reduction by oxygen. The series. Reactions with water and acids. Displacement. Then four examiner traps from real Paper 1 mark schemes (Jun 22, Jun 23, Jun 24).

Key Definitions

Reactivity Series

A list of metals arranged in order of their reactivity, from most reactive at the top to least reactive at the bottom.

Oxidation (GCSE)

The gain of oxygen by a substance.

Reduction (GCSE)

The loss of oxygen by a substance.

Displacement Reaction

A reaction in which a more reactive metal displaces a less reactive metal from its compound (usually a salt solution).

Metal + Oxygen → Metal Oxide

When metals react with oxygen, they form metal oxides. The more reactive the metal, the more vigorous the reaction.

2Mg + O₂ → 2MgO brilliant white flame

4Fe + 3O₂ → 2Fe₂O₃ slow — rusting

2Cu + O₂ → 2CuO only on heating, no flame

Mark-Scheme Phrasing

"Magnesium reacts more vigorously than iron with oxygen because it is higher in the reactivity series." Always link vigour to position — both halves of the sentence are needed.

Oxidation & Reduction (Oxygen Definition)

At GCSE — and on Foundation tier — oxidation and reduction are defined by oxygen, not electrons. Electron-transfer redox is HT-only and comes in 4.02.

EXAMINER ALERT — P1 Jun 2023 Q09.1

The substance reduced is Fe₂O₃ (iron oxide) — NOT iron. Iron oxide is what loses the oxygen; iron itself is the product. "Only a tenth of students scored both marks... Most students gave incorrect responses for the substance reduced: usually iron, but sometimes carbon." The mark scheme rule: "MP2 is dependent upon MP1 being awarded" — name the wrong species and you lose both marks.

The Reactivity Series

Memorise this list — it is the foundation for almost every reactivity question on Paper 1.

K

Potass.

Na

Sodium

Li

Lithium

Ca

Calcium

Mg

Magn.

Al

Alum.

C

Carbon

Zn

Zinc

Fe

Iron

H

Hydro.

Cu

Copper

Ag

Silver

Au

Gold

← MOST REACTIVE

LEAST REACTIVE →

Memory Tip — Group, Don't Memorise Blind

K, Na, Li, Ca, Mg are the spec's "very reactive" group — react with cold water. Al is conventionally included (protected by oxide layer). C and H are the two threshold reference points (extraction / acids). Zn, Fe are mid-reactivity. Cu, Ag, Au are the unreactive "jewellery metals" at the bottom. Spec-named metals: K, Na, Li, Ca, Mg, Zn, Fe, Cu — these eight you must know.

Why Are Metals Reactive?

The spec gives you the answer in one sentence: "The reactivity of a metal is related to its tendency to form positive ions."

The Core Idea

When a metal reacts, its atoms lose electrons to form positive ions. The more easily a metal forms its positive ion, the more reactive it is — and the higher it sits in the reactivity series.

M → Mⁿ⁺ + n e⁻ (metal atom → metal ion + electrons)

Top of the Series

K, Na, Li form 1+ ions very easily → react vigorously with cold water and acids.

Bottom of the Series

Cu, Ag, Au hold onto their electrons → barely form positive ions → unreactive even with acid.

Spec Learning Outcome

"Explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion." If a 3-mark "explain" question asks why one metal is more reactive than another, the answer must mention forming positive ions / losing electrons more readily.

Reactions with Water

Per the spec, reactions are limited to room temperature — steam reactions are not examined at GCSE.

MetalReaction with cold water

K, Na, Li, CaVigorous → metal hydroxide + H₂ (fizzing, floats, may ignite)

MgVery slow (a few bubbles over hours)

Zn, Fe, Cu, Ag, AuNo reaction

2Na + 2H₂O → 2NaOH + H₂

Ca + 2H₂O → Ca(OH)₂ + H₂

Mark-Scheme Observation Phrases (Group 1 + water)

"Floats / moves on the surface", "fizzes / effervescence (H₂ gas)", "metal disappears / gets smaller", "(K) lilac flame / burns" — name two distinct observations for a 2-mark question.

Reactions with Dilute Acids

metal + acid → salt + hydrogen

Whether the reaction happens depends on one rule:

✓ Above Hydrogen

Reacts. K, Na, Li, Ca, Mg, Al, Zn, Fe all give salt + H₂. Vigour decreases going down — link vigour to position.

✗ Below Hydrogen

No reaction. Cu, Ag, Au cannot displace hydrogen from acid.

Mg + 2HCl → MgCl₂ + H₂

Zn + H₂SO₄ → ZnSO₄ + H₂

Cu + HCl → NO REACTION

The Salt's Name Depends on the Acid

HCl → metal chloride. H₂SO₄ → metal sulfate. HNO₃ → metal nitrate. Always identify which acid is used before naming the salt.

Displacement Reactions

A more reactive metal displaces a less reactive metal from a solution of its salt.

Two Observations to Score

(1) Blue colour fades / becomes colourless. (2) Reddish-pink copper is deposited. Both are needed for the 2-mark "describe what you observe" question.

Worked Example — Explain Displacement

Q: Explain why magnesium reacts with copper sulfate solution but silver does not.3 MARKS

Use the PEE Structure

PMagnesium displaces copper from copper sulfate; silver does not.EMagnesium is more reactive than copper (higher in the reactivity series); silver is less reactive than copper (lower in the series).EA more reactive metal can displace a less reactive metal from its compound; a less reactive metal cannot.

Mark-Scheme Phrases

Use either "more reactive than" OR "higher in the reactivity series". Name each metal explicitly — never write "it" in a comparison.

Trap 1 — "Transition Metal" ≠ Reactivity

Real Paper 1 question. P1 Jun 2024 Q01.6: Explain why copper cannot be used to make a sulfate by reacting with sulfuric acid.1 MARK

"Many described copper as a transition metal but did not link that to reactivity in any way... Only a sixth of students scored both marks, with half not gaining credit at all." — AQA Examiner Report, P1 Jun 2024 Q01.6

✗ Loses Mark

"Copper is a transition metal so it doesn't react."

Category, not reactivity. The mark requires position.

✓ Earns Mark

"Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from the acid."

Also Accepted (MS)

"Copper does not react with (sulfuric) acid" / "is unreactive" / "will not displace hydrogen". Note: "Not reactive enough" is ignored — too vague.

Trap 2 — "Too Reactive" Needs a Consequence

Same question, second mark. P1 Jun 2024 Q01.6: Explain why sodium is not suitable for making sodium sulfate by reacting with sulfuric acid.1 MARK

"Some did not go far enough; they simply stated that sodium is too reactive without saying why that is a problem." — AQA Examiner Report, P1 Jun 2024 Q01.6

✗ No Mark

"Sodium is too reactive."

Just rewords the question. No consequence stated.

✓ Earns Mark

The reaction "could explode" OR "could get too hot" OR "(is) dangerous".

Verbatim from MS — pick any one.

The Pattern

Whenever a question asks why a reactive metal is "unsuitable", you must state the safety consequence. The Jun 2024 mark scheme accepts "could explode", "could get too hot", or "(the reaction is) dangerous". "Too reactive" alone is ignored.

Trap 3 — Ambiguous "It"

P1 Jun 2022 Q07.1: Given that 2C + SiO₂ → Si + 2CO, explain what this shows about silicon's position in the reactivity series.2 MARKS

"There was, however, some ambiguous use of the word 'it' such as 'it shows that it is below carbon because it displaces it'. If it was not clear what 'it' referred to, credit was not given." — AQA Examiner Report, P1 Jun 2022 Q07.1

✗ Loses Marks

"It shows that it is below carbon because it displaces it."

Four pronouns — examiner cannot tell which substance is which.

✓ Scores Both Marks

"Silicon is less reactive than carbon, because carbon displaces silicon from silicon dioxide."

Discipline (Applies to Every Reactivity Comparison)

Whether the question is about metals + salts, or non-metals like silicon + carbon — name both species, name what is displaced from what. The same rule kills marks in every Module 4 reactivity question.

Trap 4 — Name the Right Species

P1 Jun 2023 Q09.1: "Iron is extracted from iron oxide by a displacement reaction with carbon. The equation is Fe₂O₃ + 3C → 2Fe + 3CO. Which substance is reduced? Give one reason for your answer. Answer in terms of oxygen."2 MARKS

"Students found this question difficult, with only a tenth of students scoring both marks. Most students gave incorrect responses for the substance reduced: usually iron, but sometimes carbon." — AQA Examiner Report, P1 Jun 2023 Q09.1

✗ Loses Both

"Iron is reduced because it loses oxygen."

Iron is the product, not the reactant. Fe is what's already without oxygen — it's Fe₂O₃ that loses it.

✓ Scores Both

"Fe₂O₃ (iron oxide) is reduced because it loses oxygen."

Mark-Scheme Rule

MP2 (the reasoning mark) is dependent on MP1 being correct. If you name the wrong substance, you lose both marks even if your reasoning is right. The MS also says: "ignore Fe³⁺ gains electrons" — at HT, don't reach for OIL RIG when the question says "in terms of oxygen".

Mark-Scheme Phrases to Memorise

Word-for-word language that scores on Paper 1. Use these phrases — don't paraphrase them.

ConceptVerbatim mark-scoring phraseDon't write

Why Cu doesn't react with acid"copper does not react with (sulfuric) acid" / " below hydrogen in the reactivity series" / "will not displace hydrogen""transition metal" alone; "not reactive enough" (ignored)

Why Na is unsuitable" could explode " / "could get too hot" / "(is) dangerous""too reactive" alone (no consequence)

Why a metal is more reactive (3-mark)"forms positive ions more readily" / "loses electrons more easily"just naming position without mechanism

Displacement" [Metal A] is more reactive than [Metal B] " / "[A] displaces [B] from [B's compound]""it displaces it"

Zn + CuSO₄ observation"blue colour fades / (becomes) colourless"; "(reddish/pink) copper deposited""changes colour"

Reduction (oxygen def.)" [oxide] loses oxygen""the metal is reduced"; HT electron answers when asked "in terms of oxygen"

Practice 1

Some sulfate salts can be made by reacting a metal directly with dilute sulfuric acid.

(a) Explain why copper cannot be used to make a sulfate this way.1 MARK

(b) Explain why sodium is not suitable for this experiment.1 MARK

a / 1

Copper "does not react with (sulfuric) acid".

Also accepted (MS): "is unreactive" / "will not displace hydrogen" / "is below hydrogen in the reactivity series". Ignored: "is not reactive enough".

b / 1

The reaction "could explode" OR "could get too hot".

Also accepted (MS): "(the reaction is) dangerous". The MS verbatim allows three phrases — pick any one.

⚠️

Examiner note (Jun 2024 ER): "Only a sixth of students scored both marks." Common mistake: "transition metal" alone (a) and "too reactive" alone (b) both score zero. Position-or-no-reaction (a); explicit consequence (b).

Practice 2

X sulfateY sulfateZ sulfate

Metal X—No reactionReaction

Metal YReaction—Reaction

Metal ZNo reactionNo reaction—

most reactive first

3 MARKS

1

Order: Y > X > Z (most → least reactive).

2

Y displaces X and Z from their sulfate solutions, so Y is the most reactive.

3

X displaces Z but does not displace Y, so X is more reactive than Z but less reactive than Y. Z does not displace either, so Z is least reactive.

⚠️

Spec skill: "deduce an order of reactivity of metals based on experimental results". Always name each metal when you describe the displacement — never write "it".

Summary

The Reactivity Series (with Lithium)

K · Na · Li · Ca · Mg · Al | C | Zn · Fe | H | Cu · Ag · Au

Spec-named metals (must know): K, Na, Li , Ca, Mg, Zn, Fe, Cu

C and H are reference points: above C → extracted by electrolysis (4.02); above H → reacts with dilute acid; below H → no acid reaction

Why Reactive? — Positive Ions

Reactivity = tendency to form positive ions (M → Mⁿ⁺ + ne⁻)

More reactive metals lose electrons more readily → form ions more easily → react more vigorously

This is the spec's required "explain how reactivity is related to..." answer at GCSE

Reactions (Room Temperature Only — Spec)

+ Oxygen: all → metal oxide. Vigour ↓ down the series

+ Cold water: K, Na, Li, Ca → vigorous; Mg → very slow; rest → no reaction. Steam not examined per spec.

+ Dilute acid: above H → salt + H₂; below H (Cu, Ag, Au) → no reaction

Displacement: more reactive metal displaces less reactive from its compound

Redox by Oxygen (GCSE — non-HT definition)

Oxidation = gain of oxygen · Reduction = loss of oxygen

In Fe₂O₃ + 3C → 2Fe + 3CO : Fe₂O₃ reduced (loses O), C oxidised (gains O)

P1 Jun 2023 Q09.1: only 10% scored both marks — most wrote "iron is reduced" (it's iron oxide )

Four Examiner Traps

Trap 1 (Cu + acid): "transition metal" alone — say "below hydrogen" or "does not react with acid"

Trap 2 (Na safety): "too reactive" alone — say "could explode" / "could get too hot" / "dangerous"

Trap 3 (pronouns): "it displaces it" — name each species explicitly

Trap 4 (redox species): "iron is reduced" — should be "iron oxide is reduced"

Exam Tip

The single root cause across all four traps: students name a thing, but don't link it to position or consequence. Every reactivity answer must include either where the metal sits (position-based) or what would go wrong (consequence-based). Position OR consequence — never just the bare label.