Coordination Compounds — Chemistry STD 12 Science — Question

In the coordination compound, the species surrounding the central metal atom or ion are called ligands.
Postulates of Werner’s theory:
a. Two types of valencies are shown by most metallic elements:
(1) Primary valence or principal valence
(2) Secondary valence.
b. The tendency of every metal is to satisfy both primary and secondary valences.
c. The number of secondary valence shown by each metal is fixed.
d. The secondary valence is always directed towards fixed positions in space.