BRAINCAKEGroup 7
Revision notes for Group 7 in AQA Chemistry (7404). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- HalogensGroup 7 elements are called the Halogens.
- Physical PropertiesThe halogens exist as diatomic molecules X2 at room temperature and pressure.
- Size of AtomsThe atomic radius increases down the group as each atom has an extra filled main level compared with the one above.
- ElectronegativityElectronegativity is the ability of a bonded atom to attract the pair of electrons in a covalent bond.
- Melting and Boiling PointsThe halogens exist as diatomic molecules X2 at room temperature and pressure.
- Trends in Oxidising AbilityThe halogen acts as the oxidising agents.
- Displacement ReactionsA more reactive halogen will displace a less reactive halide from a solution of its salt.
- Halide Ions as Reducing AgentsFluorine is the most powerful oxidising agent and Iodine is the least powerful oxidising agent.
- Sodium Chloride with Sulfuric AcidNo redox reactions are occurring.
- Sodium Bromide with Sulfuric AcidThe sulfuric acid acts as an acid and donates a proton to the halide.
- Sodium Iodide with Sulfuric AcidThe sulfuric acid acts as an acid and donates a proton to the halide.
- Reaction with WaterDisproportionation is a reaction when one element undergoes oxidation and reduction at the same time.
- Reaction with AlkaliDisproportionation is a redox reaction in which the same element is both oxidised and reduced.
- Example Question - 1Question: Chlorine water is added to aqueous potassium bromide.
- Example Question - 2Question: Describe how acidified silver nitrate solution and ammonia solution can be used to identify chloride, bromide and iodide ions.
- Example Question - 3Question: Explain the different products formed when solid sodium chloride and solid sodium iodide react with concentrated sulfuric acid.
- Silver Nitrate Test for Halide IonsThe silver nitrate test identifies halide ions (Cl−, Br− and I−) in solution.
- Colours of Silver Halide PrecipitatesWhen acidified silver nitrate is added to a solution of a halide, the colour of the silver halide precipitate identifies the halide ion.
- Distinguishing Silver Halides with AmmoniaBecause the colours of the silver halide precipitates can be hard to tell apart, ammonia solution is added to the precipitate to confirm which…
- Why Nitric Acid is Added FirstIn the silver nitrate test, dilute nitric acid is added to the sample before the silver nitrate.
On the specification
- 3.2.3.1 Trends in properties
- 3.2.3.2 Uses of chlorine and chlorate(I)