The Reactivity Series
Order common metals in the reactivity series and explain how a more reactive metal displaces a less reactive one; describe how carbon is used to extract metals from their oxides in industry
What a learner can do afterwards
- Recalls the order of common metals in the reactivity series (potassium to gold)
- Predicts whether a displacement reaction will occur given two metals
- Explains why carbon can be used to extract iron from iron oxide but not aluminium from aluminium oxide
- Links the reactivity series to the history of metal use (gold found free, iron smelted, aluminium electrolytic)
1 · Read
Metals can all look shiny and bendy, but they differ in how readily they react with other substances. Chemists arrange common metals into a list called the reactivity series, ordered from the metal that reacts most readily down to the one that reacts least readily. Potassium sits at the top, and gold sits at the bottom, which is why a gold ring keeps its shine.
Zinc sits above copper in the reactivity series, so zinc is more reactive. Drop a strip of zinc into blue copper sulfate solution and the zinc pushes the copper out, leaving copper metal on the zinc. Iron also sits above copper in the reactivity series, so iron is more reactive than copper. In a suitable solution, a more reactive metal can displace a less reactive metal from its compound, when conditions allow the reaction to happen.
Reactivity also explains how metals get separated from their ores, materials with metals worth extracting. Carbon can take oxygen away from any metal below carbon in the reactivity series, so heating iron oxide with carbon leaves iron behind, though that iron is not pure. Aluminium sits above carbon, so carbon cannot pull oxygen away from aluminium oxide. Instead, factories use electrolysis, which passes electricity through purified alumina in a molten electrolyte.
One way to remember the order: Please Send Cats Monkeys And Cute Zebras In Cars, Silly Goose, for potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, copper, silver, gold. That order matches history too: gold sits so low that people found lumps of gold metal in riverbeds thousands of years ago, iron needed carbon and fire to smelt, and aluminium was costly and hard to obtain as metal until electrolysis was invented in the 1800s.
Aluminium was first obtained in small amounts by chemical reduction, using another reactive metal, before factories used electrolysis. Electrolysis later made aluminium production practical on a large scale. Iron sits below carbon, so carbon and fire can extract it, while aluminium sits above carbon, so carbon cannot extract it. Aluminium is common in Earth's crust, but it was costly and hard to obtain as metal before that large-scale method.
The reactivity series ranks metals from most to least reactive, and that ranking decides which metal displaces another and which ones carbon alone can pull free from their oxide.
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