BRAINCAKEGroup 7
Revision notes for Group 7 in Edexcel Chemistry (8CH0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Group 7 ElementsGroup 7 elements are called The Halogens.
- Trends in Melting and Boiling TemperatureThe halogens exist as diatomic molecules X2 at room temperature and pressure.
- Trend in ElectronegativityElectronegativity is the ability of a bonded atom to attract the pair of electrons in a covalent bond The Pauling scale used is from 0 - 4.
- Trend in ReactivityReactivity decreases down the group.
- Reactions with Group 1 and 2 MetalsThe most vigorous reactions are between Caesium (low first I.E.) and Fluorine (very small, only needs to gain one electron).
- Halogen-Halide Displacement ReactionsThe more reactive halogen displaces the less reactive halogen from its compound in aqueous solution.
- Halogen Disproportionation ReactionsDisproportionation is a reaction when one element undergoes oxidation and reduction at the same time. • Chlorine with water: Cl2 + H2O → HCl + HClO…
- Reaction of Halides with Sulfuric AcidSulfuric Acid Concentrated sulfuric acid dissociates in two stages.
- Sodium ChlorideIn the reaction of sodium chloride with sulfuric acid, no redox reactions are occurring.
- Sodium BromideIn the reaction of sodium bromide with sulfuric acid, the sulfuric acid acts as an acid and donates a proton to the halide.
- Sodium IodideIn the reaction of sodium iodide with sulfuric acid, the sulfuric acid acts as an acid and donates a proton to the halide.
- Test for Halide IonsTo test for halide ions silver nitrate is added to a solution of the halide.
- Hydrogen Halides as AcidsHydrogen halides readily react with water to form acidic solutions.
- Reaction with AmmoniaHydrogen halides all react with ammonia gas to form white ionic salts.
On the specification
- Topic 4B: The elements of Group 7 (halogens)