Cobalt II chloride CoCl is a coordination compound in which cobalt has a +2 oxidation state. The electronic configuration of cobalt in its ground state is [Ar] 3d 4s. When cobalt loses two electrons to form the Co ion, its electronic configuration becomes [Ar] 3d.The color of cobalt II chloride is influenced by the crystal field splitting of the d orbitals in the Co ion. In an octahedral environment, such as in CoCl, the five d orbitals split into two groups: the lower-energy tg orbitals dxy, dyz, and dxz and the higher-energy e_g orbitals dz and dx-y . The energy difference between these two groups of orbitals is called the crystal field splitting energy .In CoCl, the Co ion has an electronic configuration of tg e_g. When the compound absorbs light, an electron from the tg orbitals can be promoted to the e_g orbitals. The energy of the absorbed light corresponds to the energy difference between the tg and e_g orbitals. The remaining wavelengths of light are transmitted or reflected, and this is what we perceive as the color of the compound.Cobalt II chloride is typically blue in the anhydrous form and pink or purple in the hydrated form CoCl6HO . The color change is due to the change in the crystal field splitting energy caused by the different ligands chloride ions in anhydrous CoCl and water molecules in hydrated CoCl6HO .At various concentrations, the color of cobalt II chloride solutions can range from pale pink to deep blue. The color depends on the concentration of the Co ions and the nature of the ligands present in the solution. As the concentration of Co ions increases, the color of the solution becomes more intense. Additionally, the presence of other ligands, such as chloride ions or ammonia, can cause the color to shift due to changes in the crystal field splitting energy.