Explain why complexes formed from transition metal ions are coloured.
- AQA - A-Level Chemistry - Question 3 - 2020 - Paper 3
Question 3
Explain why complexes formed from transition metal ions are coloured.
Worked Solution & Example Answer:Explain why complexes formed from transition metal ions are coloured.
- AQA - A-Level Chemistry - Question 3 - 2020 - Paper 3
Step 1
M1: Explain absorption of light
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Answer
Complexes formed from transition metal ions are coloured because they absorb specific wavelengths of visible light. This occurs when electrons in the d-orbitals of the metal ions are promoted to higher energy levels due to the absorption of light photons. The wavelengths of light that are not absorbed will be reflected or transmitted, giving the complex its characteristic colour.
Step 2
M2: Promote electrons in d-orbitals
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Answer
The absorption of light promotes electrons from the lower-energy d-orbital to a higher-energy d-orbital. This electronic transition is responsible for the specific colour observed.
Step 3
M3: Explain complementary colours
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Answer
The colour seen in a complex is complementary to the wavelength of light it absorbs. Therefore, if a complex absorbs light in the red region, it will appear green, as green is the complementary colour to red.
