Stability and Colors in coordination compounds

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chemistry 12th class cbse notes

The stability of the coordination compound depends on

Nature of the ligand:

Chelating ligands form strong and more stable complexes than the monodentate ligands. The π-  bond ligands forms more stable complexes than the σ- bonded complex.

Nature of the metal atom/ion:

Small, highly charged metal ions form more stable complexes than large size, lowly charged metal ion.

Color in Coordination Compounds

  • The crystal field theory attributes the colour of the coordination compounds to d-d transition of the electron, i.e., the transiton of electron from t2g level to the higher eg level which accompanies the absorption of light in visible spectrum.
  • In the absence of ligands, crystal field splitting does not occur and hence the substance is colourless.

Color in Coordination Compounds

Limitations of crystal field theory

  • It does not take into account the partly covalent character of bonding between the ligand and the central atom.
  • It is also unable to explain the relative strengths of ligands e.g., it does not explain why H2O is stronger ligand than OH.

 

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