Group 7, The halogens

1. Decreases down group
   1. The shared electrons are further away from nucleus as size increases down group, more shielding so counteract increasing nuclear charge, so electronegativity decreases down the group

1. Increases down group

1. Increases down group
   1. Larger atoms, so more VDW
   2. The lower the BP the more volatile

1. Halogens are oxidising agents and are reduced themselves
   1. Oxidising ability decreases down the group
2. Displacement reaction
   1. When metal halides (in solution) react with halogens, the halide in the compound will be displaced by a more reactive halogen - not by a less reactive one

1. Reducing agent
   1. Reducing power increases down group
      1. The larger the ion the more easily it loses electrons
2. Sodium halides & Conc. sulphuric acid

   Attachments:

   • Halide reactions

Attachments:

• Silver nitrate test

1. When oxidation states of atoms increase and decrease within a reaction it is called disproportionation
2. Purifying water, chloric acid kills bacteria
3. Alternative
   1. sodium or calcium chlorate - forms chloric acid in water
      1. Slightly acidic conditions to maintain equilibrium