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.
|Halogen||Formula||Colour||State at room temperature and pressure|
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.