Topic 5 of 7
Build the metal reactivity series from experiments
More reactive metals form positive ions more readily.
O-Level 6092 (2026) / SEC G3 K324 (2027)
Build the metal reactivity series from experiments
More reactive metals form positive ions more readily.
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.
| Metals | Water or steam | Dilute HCl |
|---|---|---|
| K, Na, Ca | React with cold water; hydroxide and hydrogen form | Very vigorous reaction; acid is not a suitable routine comparison |
| Mg | Very slow with cold water; heated magnesium reacts with steam to give MgO and H2 | Reacts readily |
| Zn, Fe | React with steam when strongly heated | React to give a chloride and hydrogen |
| Pb | No appreciable reaction with water or steam in the usual school comparison | Reaction may be slow or stop as insoluble PbCl2 coats the surface |
| Cu, Ag | No reaction with water or steam | Do not liberate hydrogen |
A higher position in the metal reactivity series means a greater tendency of a metal atom to lose electrons and form its positive ion. In an aqueous displacement, the added metal is oxidised and the displaced metal ion is reduced. In an oxide displacement, the more reactive metal takes oxygen from the less reactive metal oxide. Use the stated conditions: very reactive metals in water may react mainly with water instead of providing a clean displacement comparison.
A more reactive metal displaces a less reactive one from its aqueous ions: Fe(s) + Cu2+(aq) -> Fe2+(aq) + Cu(s). Iron loses electrons; copper ions gain them. A more reactive metal can also remove oxygen from a less reactive metal oxide, for example Mg(s) + CuO(s) -> MgO(s) + Cu(s) on heating.
Worked example
Deduce an order without memorising it
Under comparable conditions, A reacts rapidly with dilute HCl, B reacts slowly, and C does not react.
- The evidence places A and B above hydrogen and C below it, assuming no passivating coating.
- The rates suggest A is more reactive than B, but comparable surface area and temperature matter.
- A displacement experiment can give additional evidence.
A > B > H > C is supported under the stated conditions. Surface coatings, such as on lead, can complicate rate comparisons.