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Question
What is the spectrochemical series?
Solution
Crystal field splitting, Δ0 depends on the field produced by the charge present on the ligand and the metal ion. Some ligands can produce strong fields and in such a case the splitting is more, while others produce weak fields due to which the splitting of d-orbitals is less. Generally, ligands can be arranged in a series in the order of their increasing field strength as follows:
\[\ce{I^- < Br^- < SCN^- < Cl^- < S^2- < F^- < OH^- < C2O^{2-}_4 < H2O < NCS^- < EDTA^{4-} < NH3 < en < CN^- < CO}\]
This type of series is called a spectrochemical series. It is determined by experimental facts based on the absorption of light by complexes formed with different ligands.
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