Question

Write the postulates of Werner’s theory.

Answer 1

In a complex, every metal atom possesses two types of valency.

(i) Primary Valency

(ii) Secondary Valency

Sr. No.	Primary Valency	Secondary Valency
1.	Primary valency refers to the oxidation state of metal ion.	Secondary valency refers to the coordination number of metal ion.
2.	Always satisfied by negative ions.	Satisfied by negative ions, neutral molecules or positive ions.
3.	These ions are generally written outside the bracket are called counter ions.	These ions written inside the bracket are called ligands.
4.	The outer sphere in which these ions present are called ionisation sphere.	The inner sphere in which these ions present are called the coordination sphere.
5.	The groups present in this sphere are loosely bound to the central metal ion and can be separated into ions.	The groups present in this sphere are firmly attached to the central metal atom and can not be separated into ions.
6.	This Valency is ionisable.	This valency is non-ionisable.
7.	This valency is non-directional	This valency is directional and determines the geometry of the complex.