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K326 / K328 / 2027
Periodicity and Metals

Lesson 6 of 8

Build the metal reactivity series from experiments

More reactive metals form positive ions more readily.

O-Level 5086 / 5088 (2026) / SEC G3 K326 / K328 (2027)

  • I can order prescribed metals.Syllabus

    Syllabus K326 / K328, 8.3(a). Order prescribed metals

  • I can deduce reactivity from data.Syllabus

    Syllabus K326 / K328, 8.3(b). Deduce reactivity from data

Build the metal reactivity series from experiments

More reactive metals form positive ions more readily.

Make a guess. You are not marked.

An iron nail is left in blue copper(II) sulfate solution. What happens?

  1. A brown coating forms on the nail and the blue colour fades
  2. The nail gets a silver coating and the solution turns colourless at once
  3. Nothing happens, because the nail is solid
Show the answer

A brown coating forms on the nail and the blue colour fades

Iron is more reactive than copper, so it displaces copper from the solution. Copper coats the nail, and fewer blue copper(II) ions remain.

The prescribed order is K, Na, Ca, Mg, Zn, Fe, Pb, H, Cu, Ag, from most to least reactive. Hydrogen is a reference point, not a metal. Compare reactions under the same conditions: a larger surface area or higher temperature can make a reaction look faster without changing the underlying reactivity order.

Evidence from water and dilute hydrochloric acid
MetalsWater or steamDilute HCl
K, Na, CaReact with cold water; hydroxide and hydrogen formVery vigorous reaction; acid is not a suitable routine comparison
MgVery slow with cold water; heated magnesium reacts with steam to give MgO and H2Reacts readily
Zn, FeReact with steam when strongly heatedReact to give a chloride and hydrogen
PbNo appreciable reaction with water or steam in the usual school comparisonReaction may be slow or stop as insoluble PbCl2 coats the surface
Cu, AgNo reaction with water or steamDo not liberate hydrogen

Worked exampleDeduce an order without memorising it

Under comparable conditions, A reacts rapidly with dilute HCl, B reacts slowly, and C does not react.

Try it first. Then show the worked stepsHide the worked steps
  1. The evidence places A and B above hydrogen and C below it, assuming no passivating coating.
  2. The rates suggest A is more reactive than B, but comparable surface area and temperature matter.
  3. A displacement experiment can give additional evidence.
Answer

A > B > H > C is supported under the stated conditions. Surface coatings, such as on lead, can complicate rate comparisons.

Check your understanding

Why does copper not produce hydrogen with dilute hydrochloric acid?

  1. Copper is below hydrogen in the reactivity series, so it cannot displace it.
  2. Copper has an oxide coating, like aluminium, which stops the acid reaching it.
  3. Hydrochloric acid is too weak an acid to react with a metal as hard as copper.
Show the answer

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

Only metals above hydrogen displace it from dilute acids. Copper is less reactive than hydrogen, so no hydrogen forms.