explain the experimental facts that cannot be explained by the simple model of werners theory
Answers
In 1923, Werner discovered a theory that describes the structure and formation of complex compounds or coordination compounds. He also got a noble prize because of this theory and he is also known as the "father of coordination chemistry".
Postulates of Werner's theory- the central metal atom in coordination compounds shows two types of valency.
1. The primary valency relates to the oxidation state and the secondary valency relates to the coordination number.
2. The number. of secondary valency is fixed for every metal atom . It means that the coordination no. is fixed.
3. The metal atom works towards satisfying both primary and it's secondary valencies.
4. A negative ions satisfy the primary valency. On other hand a negative ions or neutral molecules satisfy secondary valencies .
5. The secondary valencies points toward a fixed position in space. This is the reason behind the definate geometry of the coordinate compounds.
6. Secondary valencies determine the stereochemistry of the complex ions
And the primary valency is non directional.
Example based on Werner's theory postulates
1. CoCl3.6NH3 complex--
This is the coordination compound, in this compound coordination number of cobalt is 6and NH3 satisfy the all the 6 secondary valencies.
Chloride ions statisfy the 3 primary valencies . They are non directional in character.
These chloride ions binds and make precipitate on the addition of silver nitrate. In this case, The total no. of ions is 4 , three chloride ions and one complex ions.