Colour Changes in Transition Metal Ions

The Chemistry of Art > 4. The Transition Metals > Colour Changes in Transition Metal Ions >

Account for colour changes in transition metal ions in terms of changing oxidation states

  • Colour of transition compounds is due to absorption of specific photons of light by electrons (as outlined above)
  • The small energy differences between the d orbitals are similar to the energy of photons within the visible light range of ER
  • This absorption of certain components of white light makes a compound appear coloured
    • It exhibits the complement of the colours absorbed
    • e.g. Absorbing Red = Blue/Green (cyan) appearance
  • As each oxidation state has a different arrangement of filled and unfilled d orbitals, the range of energies from visible light it can absorb are also different
    • Which d-orbitals are full or empty
    • Which d-electrons can gain energy to occupy them