Question

Explain Werner's theory of coordinate compounds with suitable examples?

Answer 1

1) Several metals have two types of valence:
i) Primary valence or principal valence or ionisable valence. It is designated by solid line. It corresponds to oxidation number of the metal ion.
ii) Secondary valence or auxiliary valence or subsidiary valence or residual valence or non ionisable valence. It is designated by dotted line. It correspond to coordination number.
2) Every metal has tendency to satisfy both valences.
3) Every metal has fixed number of secondary valence
4) The primary valences are non-rigid and non-directional. The secondary valences are directional in nature. The secondary valence is always directed towards fixed position in space.
5) There are two spheres around the central metal ion. The inner sphere is the coordination sphere and the outer sphere is the ionization sphere.
6) Groups present in inner sphere are firmly attached to the metal ion and cannot be easily separated. The groups present in the ionization sphere are loosely bound and can be separated as ions on dissolving the complex in suitable solvent.
For example, in the complex$PtCl$${}_4$, the primary as well as secondary valencies of $Pt$ metal are $4$ each.