- In 1893 Werner produced a theory of coordination compound to explain the structure and formation of compound.
- Werner was the first inorganic chemist to be awarded Nobel prize for chemistry in1913
- Werner postulated that metal exhibits two type of valancies i.e.
(1)Primary valancy and
(2)Secondary valancy
Primary valency:
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The ligands which satisfy primary valency always ionic in nature.
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Primary valency is ionizable and non directional.
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Primary valency only satisfied by negative ions i.e. anions and are written outside the coordination sphere.
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Primary valency donot decide geometry of the coordination compound.
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Primary valency corresponds to the oxidation state of the metal ion.
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Primary valency is represented by dotted line i.e.(……….)
Secondary valency:
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The ligands which satisfy secondary valency always covalent in nature.
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Secondary valency is non ionizable and directional.
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Secondary valency is satisfied by either neutral or negative or both type of ligands.
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Secondary valency decide geometry of the complex
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Secondary valency corresponds to the coordination number of the metal ion.
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Secondary valency is represented by solid line.
Question for you:
In [Co(NH3)4Cl2]Cl chlorine ligand satisfies which type of valency.