GCSE Combined Science (AQA)

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Halogen Displacement Reactions

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Atomic structure and the periodic table The periodic table

Halogen Displacement Reactions

5:30 Group 7 Element Properties, Compounds, and Reactions
Spec 4.1.2.6 4.1.2.1
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  • In some reactions, a more reactive element displaces a less reactive element.
  • Displacement means taking the place of something.
  • Example: Element A (more reactive) can replace Element B (less reactive) in a compound containing B and X.
  • This type of reaction is called a displacement reaction.
  • Halogens often undergo displacement reactions.
  • A more reactive halogen can displace a less reactive halogen from solutions of its salts.
  • Halogen reactivity decreases down the group (Fluorine is most reactive, Tenin is least reactive).
  • Example: Chlorine + Potassium Bromide ��� Potassium Chloride + Bromine.
  • Chlorine (pale green solution) added to Potassium Bromide (colorless solution) results in an orange solution due to bromine.
  • Chlorine displaces bromine because it is more reactive.
  • Reactivity trends can predict halogen reactions with their salts.
  • Chlorine (most reactive) displaces both bromine and iodine from their salts.
  • Bromine (middle reactivity) displaces iodine but not chlorine.
  • Iodine (least reactive) does not displace any other halogens.
  • Example reaction: Lithium Bromide + Chlorine ��� Lithium Chloride + Bromine (solution turns orange).
  • Example reaction: Lithium Iodide + Bromine ��� Lithium Bromide + Iodine (solution turns brown).
  • Bromine displaces iodine because it is more reactive.
  • Chlorine added to Lithium Iodide would also turn the solution brown due to iodine displacement.

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