1. Halides
   1. Reducing agents
      1. Loses/ donates electrons
      2. Ability increases down the group.
2. Group 7
3. Oxidising agents
   1. Accepts electrons
   2. Ability decreases down the group.
4. Displacement reactions
   1. Chlorine
      1. Chlorine displaces bromide and iodide ions
      2. Topic
      3. Topic
5. A more powerfully oxidising halogen will displace a less powerfully oxidising halogen from its salt.
6. Bromine
   1. Bromine displaces iodidie ions.
   2. Subtopic 2
7. Iodine
   1. Iodine doesn't displace anything
8. Halide ions + conc sulphuric acid
9. Topic
10. Testing
    1. Add aqueous silver nitrate
11. Topic
12. Photochemical decomposition
    1. in the presence of sunlight
    2. reduces silver halide to silver metal
    3. remains as opaque image in black and white photographic film
13. Chlorine water
    1. When chlorine dissolves in water it forms a mixture of hydrochloric acid and chloric(i) acid.
    2. An equilibrium is established.
    3. It is pale green in colour (showing the presence of chlorine)
    4. Addition of alkali will remove the hydrogen ions and make more water molecules.
       1. The removal of hydrogen ions and addition of water, by Le Chatlier's principle, shift the equilibrium to the right, and the green colour will FADE. Alternatively, the addition of acid will shift the equilibrium to the left and and the green colour will intensify.