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Question
What is the spectrochemical series?
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Solution
Crystal field splitting, Δo 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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