Question:

The primary and secondary valencies of chromium in the complex ion, $dichlorodioxalatochromium \,(III)$, are respectively

Updated On: Jun 6, 2022
  • 44624
  • 44654
  • 3,6
  • 44715
Hide Solution
collegedunia
Verified By Collegedunia

The Correct Option is C

Solution and Explanation

The formula of dichlorodioxalatochromium (III) is
$ {{[Cr(C{{l}_{2}}){{(Ox)}_{2}}]}^{3-}} $
Primary valency of a metal $ (Cr) $ in the complex = oxidation number of that metal
$ =+3 $
Secondary valency of chromium in complex = coordination number
$ =+6 $
( $ \because $ Coordination number is the number of ligands attached to the central metal ion and oxalate ion is a bidentate ligand i.e, can coordinate at two positions)
Was this answer helpful?
0
0

Concepts Used:

Werner’s Theory of Coordination Compounds

In 1893 Werner produced a theory to explain the structures, formation and nature of bonding in the coordination compounds. This theory is known as Werner’s theory of coordination compounds.

Postulates of Werner's Theory:

The important postulates as observed by Alfred Werner throughout his experiments are as follows:

  • The complex/ coordination compounds contain a central metal atom.
  • The metal atoms in a coordination compound generally show two types of valency: primary valency and secondary valency.
  • The primary valencies denote the oxidation state. They are ionizable and are satisfied by the negative ions.
  • Secondary valencies denote the coordination number. They are non-ionizable and are fixed for every metal atom. The secondary valency is generally satisfied by the neutral molecules or negative ions.
  • The metal atoms should satisfy both primary and secondary valencies.
  • The secondary valency of the atom basically shows the geometry/ polyhedra of the particular coordination compound.

Limitations of Werner’s Theory:

  • Though Werner explained some properties of the coordination compound,  he failed to explain the colour of the coordinate compound.
  • He could not explain the magnetic and optical properties of coordination compounds.
  • He could not answer the question, why does the coordination sphere have a definite geometry.