halogen (thing)

Some generalistic trends among the halogens. As you go down the group -

• There's an extra shell of electrons for every row you go down.
• They're less reactive because of this.
• They're darker in colour.
• There are state changes as you go down - Fluorine and Chlorine are gases, Bromine is a liquid and Iodine is a solid.
• They have a higher melting point and a higher boiling point.

Halogens are all non-metals with coloured vapours. Halogens are poisonous. They all form molecules which are pairs of atoms, and will form both ionic and covalent bonds.