Q. Illustrate about Werners Theory?

Based on the study of a large number of compounds. Wermer gave the following postulates:

• Metal atoms in complexes possess two types of valences namely. Principal or an auxiliary or secondary.

• Primary valencies are always satisfied by anions but the secondary valencies can be satisfied either by anions and/or neutral molecules.

• Every metal atom has a fixed number of auxiliary valencies.

The secondary valencies show directional properties. In other words secondary valencies are directed in space around the central ion.