A clear visual guide to halogen displacement reactions, linking experimental observations to Group 7 reactivity, electron transfer and redox chemistry.

The resource begins with the halogen reactivity order:

Fâ‚‚ > Clâ‚‚ > Brâ‚‚ > Iâ‚‚

and explains why reactivity decreases down Group 7. As the atoms become larger and electron shielding increases, an incoming electron is attracted less strongly to the nucleus. Halogens therefore gain electrons less readily as the group is descended.

Two colourful displacement reactions are illustrated:

Chlorine + bromide ions – pale yellow chlorine water reacts with colourless sodium bromide solution to produce an orange solution of bromine.
Chlorine + iodide ions – pale yellow chlorine water reacts with colourless sodium iodide solution to produce a brown solution of iodine.

The resource includes:

Ionic equations with state symbols.
Half-equations showing electron loss and gain.
Identification of the species being oxidised and reduced.
Changes in oxidation states.
A simple explanation of displacement in terms of the tendency of halogens to gain electrons.
The relationship between halogen reactivity and oxidising ability.
Appropriate safety information for the use of chlorine water.

The key principle is:

A more reactive halogen displaces the halide ions of a less reactive halogen from solution.

The poster also reinforces the fundamental redox definitions:

Oxidation = loss of electrons
Reduction = gain of electrons

This provides an excellent companion to metal displacement reactions, where increasing metal reactivity is associated with atoms losing electrons more readily.

Suitable for GCSE, IGCSE and A-level Chemistry, particularly for teaching Group 7, periodic trends, displacement reactions, ionic equations, half-equations and redox.

A QR code links to FranklyChemistry, where students can view the corresponding animated sequence and explore further chemistry resources.