Write the basic postulates of Werner's theory.

Explanation

Basic postulates of Werner's theory :
(1) Most of the metallic elements exhibit two types of valence namely,
(i) Primary valence or principal valence
(ii) Secondary valence.
(2) Every metal tends to satisfy primary and secondary valences.
(3) Every metal has fixed number of secondary valence.
(4) The secondary valence is always directed towards fixed positions in space giving a definite structure to the coordination (complex) compound.
(5) Secondary valence is satisfied only after satisfying primary valence.