Question

Define ligand. Write four postulates of Werner’s theory.

Answer 1

Ligands: 

The molecules or ions which are coordinated to the central atom or ion in the coordination compound are called ligands or donor groups.

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.