Question

What is meant by complex compound? Describe the main points of Werner’s theory.

Answer 1

Complex compound is a type of compound formed by the association between a central metal atom along with surrounding non-metal atoms or ions or ligands bonded by covalent, ionic or co-ordinate bonds. Warner’s theory is used to describe the complex compound with their structure.

Complete step by step answer:
-A complex compound can be described as a class of substances with a chemical structure where the central atom is a metal and it is surrounded by non-metal atoms or a group of atoms (or ligands). Both the central atom and ligands are joined by chemical bonds like covalent bond, ionic bond, coordinate bond.
- Complex compound is also called a coordinate compound as it contains the coordinate bonds in its structure. Complex compounds show geometrical and optical isomerism.
Werner’s theory:
-The central metal atom of a complex compound shows two types of valency – primary and secondary.
-The primary valency describes the oxidation state of the central metal atom and the secondary valency describes the coordination number of the complex compound.
-The coordination number of a complex compound is fixed – it means the secondary valency is fixed for every metal atom.
-A negative ion of a complex compound satisfies the primary valency. On the other hand secondary valency is satisfied by the positive ions.
The secondary valency tells us about the geometric structure of a complex compound.

Note:
As all the other theories, the Werner’s theorem also has own limitation which includes following:
-It could not explain why every element does not form a coordinate compound.
-All directional properties present in a bond of coordinate compound cannot be fully described by Werner’s theory.
-Properties like the colour, magnetism and optical property of any coordinate bond could not be explained by Werner’s theory.