Question detail
Why are transition metal ions often coloured?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Transition metals (A-level only)
Question
- A. Both A and B
- B. Due to the presence of unpaired electrons in the d orbitals
- C. Because they absorb light in the visible spectrum
- D. They reflect all wavelengths of light
Answer
Both A and B
Explanation
The correct option is Both A and B. Both A and B is the best answer because it directly supports the AQA A-Level Chemistry objective to explain ligand substitution reactions. This reasoning is anchored to Complex ions and ligand substitution (A-level only) in Transition metals (A-level only), and it separates ligand from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Misunderstanding Ligand Substitution
Students often confuse ligand substitution reactions with simple displacement reactions, failing to recognize that ligands are replaced in complex ions rather than just being displaced.
To clarify ligand substitution, remember that a ligand is a molecule or ion that donates a pair of electrons to a metal ion to form a coordinate bond. In a ligand substitution reaction, one ligand is replaced by another, maintaining the coordination number of the metal ion. For example, in the reaction [Cu(H2O)6]²⁺ + 4Cl⁻ → [CuCl4]²⁻ + 6H2O, the water ligands are replaced by chloride ions.
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