Reactivity of metals · Grade 9
Metals can be put in order of how readily they react: the reactivity series. Potassium, sodium and lithium react vigorously with water; gold hardly reacts at all. The series predicts which metal displaces another from its compounds, and it decides how each metal is got out of its ore: by heating with carbon, by electrolysis, or not at all for gold.
Key facts
- The series: potassium, sodium, lithium, calcium, magnesium, aluminium, (carbon), zinc, iron, tin, lead, (hydrogen), copper, silver, gold. Carbon and hydrogen are there to compare.
- The more reactive a metal, the more easily it loses electrons to form positive ions.
- Reactive metals + water → metal hydroxide + hydrogen. Metals above hydrogen + dilute acid → salt + hydrogen; copper, silver and gold do not react with dilute acids.
- Displacement: a more reactive metal pushes a less reactive metal out of a solution of its compound. zinc + copper sulfate → zinc sulfate + copper.
- An ore is a rock containing enough metal compound to be worth extracting. Gold is so unreactive that it is found as the metal.
- Metals below carbon are extracted by heating their oxides with carbon: the oxide is reduced (loses oxygen). Metals above carbon need electrolysis.
- In displacement, the more reactive metal is oxidised (loses electrons) and the ions of the less reactive metal are reduced (gain electrons).