WERNER’S THEORY OF COORDINATION COMPOUNDS

Explanation

The main postulates of Werner's theory of coordination compounds are as follows
(a) Metals possess two type of valencies called
(i) primary valency which are ionisable (ii) secondary valency which are non ionisable
(b) Primary valency is satisfied by the negative ions and it that which a metal exhibits in the formatio of its simple salts
(c) Secondary valence are satisfied by neutral ligand or negative ligand and are those which metal exerciese in the formation of its complex ions. Every cation has a fixed number of secondary valencies which are directed in space about central metal ion in certain fixed directions e.g., in `CoCl_(3)-6NH_(3)` valencies between Co and Cl are primary valencies and valencies between Co and `NH_(3)` are secondary in `COCl_(3)-6NH_(3)` six ammonia molecules linked and thus account for structure of `COCl_(3)-6NH_(3)` as follows in modern theory it is now referred as coordination number of central metal atom or ion.