Group 7 (VII) – The halogens

The Periodic Table - Group 7 Halogens

Group 7 elements exist as simple, diatomic (two-atom) molecules. Each molecule is made up of a pair of halogen atoms, linked by a single, covalent bond.

Halogens are toxic. You should use a fume cupboard if you are using them in experiments.

HalogenFormulaColourState at room temperature and pressure
fluorineF2yellowgas
chlorineCl2yellow-greengas
bromineBr2red-brownliquid
iodineI2grey-blacksolid
astatineAt2--
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You will notice that, moving down Group 7, the element become darker in colour and change from gas to liquid to solid. This is because elements lower in the group have higher melting points.

Iodine sublimation

Iodine is a grey-black solid at room temperature and pressure. If heated, it sublimes to form a purple iodine gas. Sublimation is the change of state from solid directly to gas on heating, without passing through the liquid phase.

Test for chlorine gas

Damp universal indictor paper changes to red and then bleaches white in the presence of chlorine gas.