Group 7 — The Halogens

This lesson covers the Group 7 elements (the halogens) as required by the Edexcel GCSE Chemistry specification (1CH0), Topic 6: Groups in the Periodic Table. You need to know the physical properties of the halogens, their trend in reactivity, and how they react with metals. You must also be able to explain the reactivity trend using electron configuration.

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The Group 7 Elements

Group 7 is found on the right-hand side of the periodic table, one column to the left of the noble gases. The halogens are non-metals that exist as diatomic molecules (molecules made of two atoms bonded together).

Element	Symbol	Molecular Formula	Atomic Number	Electron Configuration
Fluorine	F	F₂	9	2, 7
Chlorine	Cl	Cl₂	17	2, 8, 7
Bromine	Br	Br₂	35	2, 8, 18, 7
Iodine	I	I₂	53	2, 8, 18, 18, 7
Astatine	At	At₂	85	— (radioactive, very rare)