3.1.3 halogens

Very pale yellow gas Highly reactive

Greenish, reactive gas, poisonous in high concentrations

Red liquid, gives off dense brown/orange poisonous fumes

Shiny grey solid sublimes to purple gas

Increases down group Molecules become larger, more electrons so more induced dipole-dipole forces between molecules As intermolecular forces get larger more energy has to be used to break these

Decreases down the group as atoms get bigger with more shielding so they less easily attract and accept electrons Form -1 ions less easily down the group

Very pale green solution No reaction

Yellow solution Cl displaced by Br

Brown solution Cl has displaced I

Yellow solution No reaction

Yellow solution no reaction

Brown solution Br has displaced I

Brown solution No reaction

Colourless No reaction

Yellow, Cl has displaced bromide

Purple Cl has displaced I

Yellow no reaction

Yellow No reaction

Purple Br has displaced I

Purple No reaction

Where an element is simultaneously oxidised and reduced

Used in water treatment to kill bacteria Toxic + possible formation of chlorinated hydrocarbons

Mixture of NaCl and NaClO Disinfectant, kills bacteria

Test solution is made acidic with nitric acid, then silver nitrate is added Fluorides - no precipitate Chlorides - white precipitate Bromides - cream precipitate Iodides - pale yellow precipitate