CDS Chemistry · Metals and Non-Metals
The Reactivity Series
The order of metals by reactivity, what it predicts about acids, oxygen and displacement, and why the most reactive metals are stored under oil.
Why this matters
Eight CDS questions, the largest page in the chapter. The same order, Mg > Al > Zn > Fe, was asked twice word for word (2021 and 2024), and storing sodium under kerosene was asked twice.
Concept 1 of 3: The reactivity series and reactions with acids
Definition
The series, most reactive first:
- K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Hg > Ag > Au.
- A metal above hydrogen reacts with dilute HCl or H₂SO₄ to give hydrogen gas: Mg + 2HCl → MgCl₂ + H₂.
- The higher the metal, the faster: with dilute HCl, Mg > Al > Zn > Fe.
- Nitric acid is an oxidising acid: with most metals it gives oxides of nitrogen, not hydrogen.
- A carbonate with an acid gives carbon dioxide, not hydrogen.
- Silver and gold do not react with oxygen in air; silver tarnishes by forming a sulphide, not an oxide.
| Metal | Reaction with dilute HCl | Reaction with oxygen |
|---|---|---|
| K, Na, Ca | Violent | Burn readily |
| Mg | Fast; gives H₂ | Burns with a white flameQ CDS 2018 (II): magnesium with hydrochloric acid is the pair that gives hydrogen. |
| Al, Zn, Fe | Slower in that order; gives H₂ | Form oxides |
| Pb | Very slow | Forms an oxide |
| Cu | No reaction (below H) | Forms a black oxide when heated |
| Ag, Au | No reaction | Do not form an oxideQ CDS 2020 (II): silver is the metal that does not form an oxide with oxygen. |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Metals and Non-Metals · The Reactivity Series
Nitric acid rarely gives hydrogen
Zinc sits above iron
Concept 2 of 3: Displacement: a more reactive metal pushes out a less reactive one
Definition
The rule:
- A + BX → AX + B happens only if A is more reactive than B.
- Fe, Zn and Mg all displace copper from copper sulphate (the blue colour fades).
- Copper is below lead, so copper cannot displace lead from its salts.
Displacement rule
Worked example
Practice this concept3 quick reps
The same idea in a real exam question:
Example 2 · Metals and Non-Metals · The Reactivity Series
Only the higher metal displaces
Concept 3 of 3: Why reactive metals are stored under oil
Definition
Storage rules:
- Sodium and potassium (and rubidium) are stored under kerosene, because they react violently with moisture and oxygen in air.
- Lithium is less dense than kerosene, so it floats and stays exposed. It is kept coated in paraffin wax or petroleum jelly instead.
- White phosphorus is stored under water, because it catches fire in air.
Practice this concept3 quick reps
The same idea in a real exam question:
Example 3 · Metals and Non-Metals · The Reactivity Series
Sodium is under kerosene because of moisture, not evaporation
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Formulas (1)
- Displacement: a more reactive metal pushes out a less reactive one
Displacement rule
Reference tables (2)
The reactivity series and reactions with acids6 rows
| Metal | Reaction with dilute HCl | Reaction with oxygen |
|---|---|---|
| K, Na, Ca | Violent | Burn readily |
| Mg | Fast; gives H₂ | Burns with a white flameQ CDS 2018 (II): magnesium with hydrochloric acid is the pair that gives hydrogen. |
| Al, Zn, Fe | Slower in that order; gives H₂ | Form oxides |
| Pb | Very slow | Forms an oxide |
| Cu | No reaction (below H) | Forms a black oxide when heated |
| Ag, Au | No reaction | Do not form an oxideQ CDS 2020 (II): silver is the metal that does not form an oxide with oxygen. |
Watch out for (4)
- Nitric acid rarely gives hydrogen→ The reactivity series and reactions with acids
- Zinc sits above iron→ The reactivity series and reactions with acids
- Only the higher metal displaces→ Displacement: a more reactive metal pushes out a less reactive one
- Sodium is under kerosene because of moisture, not evaporation→ Why reactive metals are stored under oil
Test yourself on Metals and Non-Metals
10 past CDS questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.