We all love the beautiful solutions that transition metals produce but why do the produce such colours (or why do non transition metals not produce colours?)
Well, it’s all to do with the d-orbitals and electrons gaining and losing energy
There are five d orbitals but they are not of equal energy – they are actually, ever so slightly split. Three d orbitals are slightly lower in energy than the other two.
Now, an electron can gain energy and jump between these split d-orbitals. Once this energy is lost, the electron will return to the ground state – and in doing so will emit visible light.