Group 7 — Halogens

This lesson covers the properties and reactions of the Group 7 elements (halogens), as required by AQA GCSE Combined Science Trilogy (8464, Chemistry 4.1.2). The halogens are fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At). You need to know their properties, reactivity trends and displacement reactions.

Physical Properties of the Halogens

The halogens are non-metals that exist as diatomic molecules ( $\text{F}_2$ , $\text{Cl}_2$ , $\text{Br}_2$ , $\text{I}_2$ ).

Halogen	Symbol	State at Room Temperature	Colour
Fluorine	$\text{F}_2$	Gas	Pale yellow
Chlorine	$\text{Cl}_2$	Gas	Green/yellow-green
Bromine	$\text{Br}_2$	Liquid	Red-brown/orange-brown
Iodine	$\text{I}_2$	Solid	Dark grey/purple vapour

Trends in Physical Properties Going Down Group 7

Melting and boiling points increase — because the molecules get larger with more electrons, leading to stronger intermolecular forces (London dispersion forces/van der Waals forces).
At room temperature, the halogens change from gas → liquid → solid going down the group.

Electronic Configuration

All halogens have seven electrons in their outer shell:

Group 7 — Halogens

Group 7 — Halogens

Physical Properties of the Halogens

Trends in Physical Properties Going Down Group 7

Electronic Configuration

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