Question

Write primary and secondary valency of $Co$ in $[Co{(N{H_3})_6}]C{l_3}$.

Answer 1

In order to find the primary and secondary valency of $Co$ in $[Co{(N{H_3})_6}]C{l_3}$, we must know what a primary and secondary valency is. The primary valency will indicate the oxidation number of the metal ion, while the secondary valency will indicate the coordination number of the metal ion.

Complete Solution :
In order to find the primary and secondary valency we can make use of Werner's theory. In his theory he stated that:
- Metal will be having two valencies namely the primary valency and the secondary valency.
- Primary valency is the number of negative ions that are equivalent to the charge that is present on the metal ions.
- Secondary valency is based on the number of the ligands attached to the central metal ion.
The primary valency is said to be ionizable whereas secondary valencies are non-ionizable.

- Now, let us find out the primary and secondary valency of $Co$ in $[Co{(N{H_3})_6}]C{l_3}$
The total number of ligands attached to the metal ion in a complex is called coordination number.
- In $[Co{(N{H_3})_6}]C{l_3}$ compound, three chlorine $C{l^ - }$ atoms present will give the primary valency and the six $N{H_3}$ molecules present will give the secondary valency i.e. the Coordination number is 6.
Therefore, in the compound $[Co{(N{H_3})_6}]C{l_3}$, the primary valency is 3 and secondary valency is 6.

Note: First find out the negative ions that surround the central metal ion. This gives us the primary valency. Then, the neutral molecule in the sphere. Do not confuse between oxidation and coordination numbers.