The reactivity series
Chemistry · Key Stage 3 · The School
An order built from evidence, not opinion
Put each metal in water, then in dilute acid, and record what happens. Potassium and sodium react violently with water; magnesium fizzes in acid; copper does nothing in either. Ranking them by how vigorously they react produces the reactivity series — potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, silver, gold.
A more reactive metal pushes a less reactive one out
Drop iron into copper sulfate solution and the blue fades while a pink-brown coating appears on the iron: iron has taken the sulfate and copper has been displaced. Do the reverse — copper into iron sulfate — and nothing happens, because copper is lower in the series. The rule is one-way, and it lets you predict a reaction before running it. One point worth being exact about: the copper does not arrive from anywhere. It was already in the solution, joined to the sulfate, and the reaction sets it free as copper metal while the iron takes its place. Nothing is created and nothing travels in — the same atoms finish the reaction rearranged.
Reactivity explains where metals are found
Gold is found as gold, in nuggets, because it is so unreactive it has not combined with anything in millions of years. Iron is found as iron oxide and aluminium as bauxite, because both reacted long ago. The more reactive a metal, the more firmly it is locked into its ore and the harder it is to get out.
And how they are extracted
Metals below carbon in the series can be pulled out by heating with carbon, which takes the oxygen — that is a blast furnace making iron. Metals above carbon hold their oxygen too tightly for that, so aluminium needs electrolysis, which needs a great deal of electricity. That is the real reason aluminium was once more precious than gold and is now worth recycling.