Provide an example of the crystal field splitting and color of transition metal complexes.

Crystal field splitting causes d-orbitals to split into different energy levels, resulting in different colours for transition metal complexes.

When transition metal ions form complexes, the d-orbitals split into two energy levels due to the presence of ligands. This splitting is called crystal field splitting. The energy difference between the two levels determines the colour of the complex.

For example, when a transition metal ion with five d-electrons, such as Fe2+, forms a complex with six ligands, the d-orbitals split into two levels: three orbitals with lower energy (t2g) and two with higher energy (eg). The energy difference between these two levels corresponds to the absorption of light in the visible region of the spectrum. In this case, the complex appears green because it absorbs red light.

Similarly, when a transition metal ion with four d-electrons, such as Ni2+, forms a complex with six ligands, the d-orbitals split into two levels: two orbitals with lower energy (eg) and three with higher energy (t2g). The energy difference between these two levels corresponds to the absorption of light in the blue region of the spectrum. In this case, the complex appears yellow because it absorbs blue light.

In summary, crystal field splitting causes d-orbitals to split into different energy levels, resulting in different colours for transition metal complexes. The energy difference between the two levels determines the colour of the complex, which can be observed through absorption spectroscopy.