Reactivity of metals
The reactivity series
The lists metals from most to least reactive. Carbon and hydrogen are included because they are useful for comparison.
Potassium > sodium > lithium > calcium > magnesium > aluminium > (carbon) > zinc > iron > tin > lead > (hydrogen) > copper > silver > gold
When metals react, they form . The more easily a metal loses electrons to form positive ions, the more reactive it is.
- Potassium, sodium and lithium react with cold water to form a metal hydroxide and hydrogen.
- Metals above hydrogen react with dilute acids to form a salt and hydrogen. The higher the metal, the more vigorous the fizzing.
- Metals below hydrogen, such as copper, silver and gold, do not react with dilute acids.
Key terms
Displacement reactions
A more reactive metal will displace a less reactive metal from a solution of its compound.
Example: magnesium in copper sulfate solution
magnesium + copper sulfate → magnesium sulfate + copper
Mg + CuSO₄ → MgSO₄ + Cu
The blue colour fades as copper ions are used up, and a brown coating of copper forms on the magnesium.
Nothing happens if the metal is less reactive: copper placed in magnesium sulfate solution does not react. Displacement reactions can be used to work out the order of reactivity.
Key terms
Extracting metals with carbon
Most metals are found in the Earth's crust as compounds in . Very unreactive metals, such as gold, are found as the metal itself.
Metals less reactive than carbon can be extracted by heating their oxide with carbon. Carbon takes the oxygen away — this is .
2ZnO + C → 2Zn + CO₂
2Fe₂O₃ + 3C → 4Fe + 3CO₂
Metals more reactive than carbon, such as aluminium, cannot be reduced by carbon. They are extracted by , which uses much more energy and is more expensive.