Why are transition metal solutions coloured? Why is copper(II) sulfate blue?

This classroom-ready ACE Illustration explains why many transition metal compounds absorb visible light and appear coloured. It shows how ligands split the d orbitals into two energy levels, allowing electrons to absorb photons of specific wavelengths and make electronic transitions.

The resource includes:

• A clear four-stage visual explanation of colour formation
• Copper(II) sulfate as a worked example
• A chain of reasoning linking ligand field splitting to the observed colour
• A simple photon energy calculation using red light (≈700 nm)
• Common examination mistakes and misconceptions
• Teacher guidance for classroom use
• Direct access to the accompanying FranklyChemistry YouTube explanation via QR code

Suitable for:

• AQA A-Level Chemistry
• OCR A-Level Chemistry
• Edexcel A-Level Chemistry
• CCEA A-Level Chemistry
• WJEC A-Level Chemistry

Ideal for whole-class teaching, revision lessons, homework, flipped learning and independent study.

This free classroom snapshot forms part of the FranklyChemistry and ACE Academy A-Level Chemistry series