Reactivity Series
Section: 9. Metals | Syllabus: Cambridge IGCSE Chemistry (0620)
The Order of Reactivity
The reactivity series lists metals in order of how readily they react - from most reactive (top) to least reactive (bottom). Two non-metals, carbon and hydrogen, are included as reference points.
| Metal (most → least reactive) | Symbol |
|---|---|
| Potassium | K |
| Sodium | Na |
| Calcium | Ca |
| Magnesium | Mg |
| Aluminium | Al |
| (Carbon) | C |
| Zinc | Zn |
| Iron | Fe |
| (Hydrogen) | H |
| Copper | Cu |
| Silver | Ag |
| Gold | Au |
K, Na, Ca, Mg, Al, (C), Zn, Fe, (H), Cu, Ag, Au
Memory aid: "Please Send Charlie's Monkeys And Cute Zebras Into Hot Countries Signed Gordon".
Why Carbon and Hydrogen Are Included
- Carbon - metals below carbon can be extracted from their ores by reduction with carbon; metals above carbon cannot (see the extraction of metals topic)
- Hydrogen - metals above hydrogen react with dilute acids to give hydrogen gas; metals below hydrogen do not react with dilute acids
Reactions with Cold Water and Steam
| Metal(s) | Reaction | Products |
|---|---|---|
| Potassium, sodium, calcium | react (increasingly vigorously) with cold water | metal hydroxide + hydrogen |
| Magnesium | reacts with steam (reaction with cold water is too slow to be significant) | metal oxide + hydrogen |
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
Mg(s) + H₂O(g) → MgO(s) + H₂(g)
Common Mistakes
- ❌ Writing that magnesium reacts readily with cold water
- ✓ magnesium's reaction with cold water is so slow it's treated as no reaction for exam purposes - only steam gives a clearly observable reaction with magnesium
Reactions with Dilute Hydrochloric Acid
Metals above hydrogen react with dilute acids to produce a salt and hydrogen gas; the reaction gets less vigorous as reactivity decreases:
| Metal | Reacts with dilute HCl? | Observation |
|---|---|---|
| Magnesium | yes | rapid, vigorous fizzing |
| Zinc | yes | steady fizzing |
| Iron | yes | slow fizzing |
| Copper, Silver, Gold | no | no reaction - all below hydrogen |
Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
Worked Example: Deducing an Order of Reactivity from Experimental Results
- Question: three metals P, Q and R were tested. P reacts with dilute HCl and its oxide is reduced by carbon. Q reacts with dilute HCl but its oxide is not reduced by carbon. R does not react with dilute HCl, but its oxide is reduced by carbon. What is the order of reactivity, most to least reactive? [1]
- Answer: Q, P, R. Q reacts with acid (above H) but its oxide resists carbon reduction (above C) - so Q is above carbon, the most reactive of the three. P reacts with acid (above H) and its oxide IS reduced by carbon (below C) - so P sits between carbon and hydrogen. R does not react with acid (below H), so it is the least reactive, even though its oxide is also reduced by carbon.
Displacement Reactions
A more reactive metal will displace a less reactive metal from a solution of its salt or from its oxide.
Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)
blue solution fades as colourless ZnSO₄ forms; brown copper is deposited
Mg(s) + CuO(s) → MgO(s) + Cu(s)
If the added metal is less reactive than the metal already in the compound, there is no reaction (e.g. Fe(s) + MgSO₄(aq) → no reaction).
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