- 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:
- The ligands which satisfy primary valency always ionic in nature.
- Primary valency is ionizable and non directional.
- Primary valency only satisfied by negative ions i.e. anions and are written outside the coordination sphere.
- Primary valency donot decide geometry of the coordination compound.
- Primary valency corresponds to the oxidation state of the metal ion.
- Primary valency is represented by dotted line i.e.(..........)
Secondary valency:
- The ligands which satisfy secondary valency always covalent in nature.
- Secondary valency is non ionizable and directional.
- Secondary valency is satisfied by either neutral or negative or both type of ligands.
- Secondary valency decide geometry of the complex
- Secondary valency corresponds to the coordination number of the metal ion.
- Secondary valency is represented by solid line.
Question for you:
In [Co(NH3)4Cl2]Cl chlorine ligand satisfies which type of valency.