# Transition metals can form compounds with different colours. Explain why transition metals are able to form coloured compounds, and state one example of a coloured transition metal compound.

> AQA A-Level Chemistry (7405) — 3.2.5 Transition metals (A-Level only) · Explain · 5 marks

> Transition metals are found in the d-block of the periodic table. Unlike Group 1 metals, transition metals have incompletely filled d sub-levels in their atoms or ions, which gives them distinctive properties.

## Mark scheme (5 marks)

1. Transition metals have incompletely filled / partially filled d orbitals (d sub-level)
2. When light falls on the compound / ion, electrons in the d orbitals absorb energy from certain frequencies / wavelengths of visible light
3. Electrons are promoted / excited to a higher energy d orbital
4. The remaining (unabsorbed) wavelengths are transmitted / reflected, and this is the colour we observe
5. A correct named example of a coloured transition metal compound, e.g. copper(II) sulfate (blue), potassium manganate(VII) (purple), iron(III) oxide (red/brown), cobalt(II) chloride (pink/blue), chromium(III) oxide (green)

## Key terms

- [transition metal](https://www.gradenine.co.uk/glossary/transition-metal)
- [coloured compound](https://www.gradenine.co.uk/glossary/coloured-compound)

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- [Revision notes for AQA A-Level Chemistry (7405)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/transition-metals-can-form-compounds-with-c255cb05) · Published by Druglandscape Ltd.