Metals and the Reactivity Series

Metals and the Reactivity Series

Understanding the Reactivity Series

  • The reactivity series is a list of metals, in order of reactivity from highest to lowest.
  • Highly reactive metals, such as potassium and sodium, are found at the top of the series, while less reactive metals, like silver and gold, are found at the bottom.
  • Metals can be arranged in the reactivity series based on their reactions with water or dilute acids (like hydrochloric acid).
  • Non-metals are not included in this series.

Reactions with Oxygen

  • All metals react with oxygen. Metals at the top of the series react vigorously, while those at the bottom show little or no reaction.
  • When a metal reacts with oxygen, a metal oxide is formed. This is a type of oxidation reaction.
  • For example, Magnesium burns in air to form magnesium oxide: 2Mg + O2 → 2MgO.

Reactions with Water

  • Not all metals react with water, but many do. Again, the reactivity of the metal determines the intensity of the reaction.
  • Reactive metals can react with water to produce a metal hydroxide and hydrogen.
  • For example, the reaction of calcium with water: Ca + 2H20 → Ca(OH)2 + H2.

Reactions with Dilute Acid

  • Many metals react with dilute acid (e.g., Hydrochloric acid - HCl) to produce a salt and hydrogen.
  • For example, Magnesium’s reaction with hydrochloric acid: Mg + 2HCl → MgCl2 + H2.
  • Extremely reactive metals like potassium, sodium, and calcium are not typically tested in this way due to the risk of explosive reactions.

Displacement Reactions

  • A displacement reaction is a type of reaction where a more reactive metal displaces a less reactive metal from its compound.
  • For example, iron can be displaced from its oxide by a more reactive metal such as aluminium:
    2Al + 3FeO → Al2O3 + 3Fe.
  • Understanding displacement reactions helps chemists to predict products of reactions and extract metals from their ores.

Extraction of Metals

  • The method of extraction depends on the reactivity of the metal.
  • Metals below carbon in the reactivity series can be extracted using reduction (using carbon) while those above need to be extracted using electrolysis.
  • For less reactive metals, extraction can often be achieved simply by heating the metal ore.
  • Most metals are found as ores, often metal oxides or sulphides. For extraction, these compounds need to be reduced to their elemental form.