The Halogens

• The elements in group 17 are known as the halogens.

• Halogens have the following properties:

• They are non-metals.

• They have relatively low melting and boiling points (they range from gases to solids).

• They produce toxic, coloured vapours.

• They exist as diatomic molecules (molecules containing two atoms).

• They have seven valence electrons, and readily attract electrons by forming ions with a charge of -1 or forming covalent compounds.

• They are highly reactive (none occur naturally in their elemental form).

• They react with hydrogen to produce toxic gases (hydrogen halides); these are covalent compounds, which dissociate into ions when dissolved in water, forming acids.

• They react with metals to form salts, which are usually soluble.

The elements in group 17 are known as the halogens.