Relative Reactivities of Metals

Relative Reactivities of Metals

The Reactivity Series

  • The reactivity series is a list of metals ranked in order of decreasing reactivity.
  • The metals at the top of the series (e.g., potassium, sodium) are more reactive than those at the bottom (e.g., gold, silver).
  • The position of a metal in the series indicates how readily it forms compounds, often via displacement reactions.

Trends in Reactivity Series

  • Displacement reactions occur when a more reactive metal displaces a less reactive metal from its compound. For instance, if copper sulphate solution (which is blue) is mixed with iron, the solution turns green due to the formation of iron sulphate and displacement of copper.
  • A more reactive metal will also displace a less reactive metal from the solution of its salt.
  • Reactivity also impacts on other types of chemical reactions. For example, highly reactive metals (like potassium and sodium) react violently with water, whereas less reactive metals (like iron or zinc) will react more slowly.

Some Key Metals in the Reactivity Series

  • Potassium: This is at the top of the reactivity series. It reacts violently with water, even with cold water, producing hydrogen gas and potassium hydroxide.
  • Magnesium: Located in the upper part of the series. It reacts with water vapour or steam to produce magnesium oxide and hydrogen but does not react with cold water.
  • Zinc: This is in the middle of the series. Though it reacts slowly with acids and doesn’t react with water, it can displace metals less reactive than it from their salt solutions.
  • Copper: It is much less reactive, found towards the bottom of the series. It doesn’t react with water and reacts slowly with acids. Copper does not displace any other metal from its salt solution because it is less reactive.
  • Gold: This is at the bottom of the reactivity series. It’s highly unreactive and does not easily form compounds. It won’t react with water, oxygen or acids under normal conditions.

Extraction of Metals and the Reactivity Series

  • Metal compounds are usually found in rocks called ores. It’s essential to consider the reactivity of the metal when planning the method for its extraction.
  • Metals below carbon in the reactivity series (like iron, zinc) can be extracted by reduction using carbon. This process involves heating the metal oxide in a furnace with carbon.
  • Metals high up in the series (like aluminium) cannot be extracted by reduction with carbon and instead are obtained by electrolysis.
  • Very unreactive metals (like gold) are found in the Earth as the free element and thus, don’t need to be extracted.