Octahedral complex of Cr (III) can have different configurations depending on the nature of the ligands attached to it. The possible configurations are sp3d2, d2sp3, and dsp2. However, the d2sp3 configuration is the most stable one.

Factors affecting configuration

The configuration of the complex depends on the following factors:

- Nature of the ligands: If the ligands attached to the central metal ion are strong, they will cause more splitting of the d-orbitals, resulting in the d2sp3 configuration. If the ligands are weak, they will cause less splitting, resulting in the sp3d2 configuration.
- Electronic configuration of the metal ion: The electronic configuration of the metal ion also plays a role in determining the configuration of the complex. For example, Cr (III) has the electronic configuration d3, which can have the d2sp3 configuration only.

Stability of d2sp3 configuration

The d2sp3 configuration is the most stable one because:

- It maximizes the number of unpaired electrons in the d-orbitals of the metal ion, which results in a magnetic moment and color.
- It minimizes the repulsion between the electrons in the d-orbitals, resulting in a lower energy state.

Colored complexes

Octahedral complexes of Cr (III) are always colored because they have unpaired electrons in the d-orbitals of the metal ion. The color of the complex depends on the nature of the ligands attached to it. Strong ligands cause more splitting of the d-orbitals, resulting in a higher energy difference between the two sets of d-orbitals, which causes the absorption of light in the visible region and gives the complex its color.

Conclusion

In conclusion, the octahedral complex of Cr (III) can have different configurations depending on the nature of the ligands attached to it, but the d2sp3 configuration is the most stable one. The complexes are always colored due to the presence of unpaired electrons in the d-orbitals of the metal ion.