What is secondary valence and how to determine the secondary valence of coordinate compounds?
The secondary valence is equal to the coordination number and is fixed for a metal. Actually,the secondary valencies are non ionisable valencies. These are satisfied by neutral molecules or negative ions.The secondary valency is fixed for a metal and is equal to the co ordination number.
The coordination number of the central atom/ion is determined only by the number of sigma bonds formed by the ligand with the central atom/ion and this gives the secondary valency too.
For ex: for, PtCl2 .2NH3 the secondary valency is equal to the co ordination no. i.e. 4.