Physical properties of the halogens

Group 7 contains non-metal elements placed in a vertical column on the right of the periodic table. The elements in group 7 are called the halogens.

Periodic table with Group 7 in red.Group 7 is on the right-hand side of the periodic table, next to group 0

The halogens show trends in their physical and chemical properties.

Physical properties

The halogens exist as simple molecules. Each molecule contains two halogen atoms joined by a single covalent bond. The table shows the colour and physical states of chlorine, bromine and iodine at room temperature.

ElementColourState
Chlorine, Cl2Pale greenGas
Bromine, Br2BrownLiquid
Iodine, I2Purple-blackSolid

The melting points and boiling points of the halogens increase going down group 7. This is because, going down group 7:

Example

The graph shows the melting and boiling points of the first four group 7 elements. Astatine is placed below iodine in group 7. Predict the melting and boiling points of astatine, and its state at room temperature.

Bar chart showing how the melting and boiling points of the halogens increase going down group 7

Astatine should have a melting point of about 300°C and a boiling point of about 340°C. This means that it will be solid at room temperature.