Explain why transition metal compounds are often coloured in solution.
The valence electrons of transition metals are found in d-orbitals. When the metal ion forms a complex with ligands the d-orbitals split into two different energy levels, and the gap between these levels happens to correspond with that of visible light.
This means that when the electrons in the lower level are promoted to the higher level part of the visible spectrum is absorbed - leading to the reflected light being coloured.
PD
Related Chemistry A Level answers
All answers ▸Why does the first ionisation energy increase across period 3?
pH and Kw question: A student dissolves 1.75g of a drain cleaner (based on NaOH) in water and makes the solution up to 100cm3. The student measures the solution pH as 13.60. Determine the percentage of NaOH in the drain cleaner, in terms of mass (g).
What is the difference between an acid and a base?
Can you give and explain the mechanism for the reaction between aqueous Sodium Hydroxide (NaOH) and Chloroethane at room temperature? What is a competing reaction which may occur and how would you promote this reaction?