Group 7 - Halogens

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  • Created by: Katy **
  • Created on: 28-12-13 13:26
  • These are non-metals
  • They exsit as diatomic molecules (as two molecules).





  • There are 7 electrons in their outershell.
  • Halogens react by gaining 1 electron to make a full outershell (opposite to Group 1 - Alkali metals in every aspect).

Cl + 1 electron → Cl-

  • Going down the group the outershell is further away from the nucleus.
  • This is why reactivity decreases going down the group.
  • Reactivity can be seen by a displacement reaction between the halogens & the halide ions.


Chloride water - Cl2(aq) → colourless most reactive

Bromine water - Br2(aq) → orange

Iodine solution - I2(aq) → brown least reactive

Halides (all colourless):

Sodium chloride solution - NaCl → Cl-(aq) most reactive

Sodium bromide solution - NaBr → Br-(aq)

Sodium iodide solution - NaI → I-(aq) least reactive

  • A more reactive halogen will displace a less


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