Question

What are the postulates of Werner's theory?

Answer 1

The following are the postulates of Werner theory:

Postulate 1: Unlike metal salts, the metal in a complex possesses two types of valencies– primary (ionizable) valency and secondary (nonionizable) valency.

Postulate 2: The ionizable sphere consists of entities which satisfy the primary valency of the metal. Primary valencies are generally satisfied by anions.

Postulate 3: The secondary coordination sphere consists of entities which satisfy the secondary valencies and are nonionizable.
The secondary valencies for a metal ion are fixed and satisfied by either anions or neutral ligands. Number of secondary valencies is equal to the coordination number.

Postulate 4: The secondary valencies have a fixed spatial arrangement around the metal ion. Two spheres of attraction in the complex [Co(NH₃)₆]Cl₃ are shown.