Question

Primary and secondary valency of platinum in the complex $\left[ {Pt{{\left( {en} \right)}_2}C{l_2}} \right]$ are:
This question has multiple correct options
A. 4, 6
B. 2, 6
C. 4, 4
D. 2, 4

Answer 1

Hint: In this question, we will use the concept of primary and secondary valency of coordination compounds. For this question we have to know what is a valency? So, the valence or valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. We will find the primary and secondary valency of a given complex to get the answer
Step-By-Step answer:.
The primary valency in coordination compounds is the number of negative ions which are equivalent to the charge on the metal ion.
The secondary valence is the number of ions of molecules that are coordinated to the metal ion or it is the number of ligands attached or coordinated to metal ions.
Here we have to find the primary and secondary valency of $\left[ {Pt{{\left( {en} \right)}_2}C{l_2}} \right]$.
Now, the primary valency is its oxidation number, i.e.
Now, oxidation state of Pt:
Charge on complex = 0
Hence,
 $
   \Rightarrow \left[ {x + (0 \times 2) + ( - 1 \times 2)} \right] = 0 \\
   \Rightarrow x + 0 - 2 = 0 \\
   \Rightarrow x = + 2 \\
$
Hence the oxidation state of Pt in the complex is +2. This is the primary valency of platinum, i.e. +2.
The secondary valency is its coordination number hence,
Platinum is bonded with two types of ligands,
Ethylenediamine which is bidentate ligand is of 2 in number hence, $2 \times 2 = 4$
Chloride which is an unindented ligand is of 2 in number hence, $2 \times 1 = 2$
Therefore, the coordination number of platinum will be, $4 + 2 = 6$. This is also the secondary valency , i.e. 6
Hence, the primary and secondary valency of platinum in the given complex is 2,6.
There is a second possibility also. The second possibility of that compound can exist as $\left[ {Pt{{(en)}_2}} \right]C{l_2}$. Hence, the primary valency can also be +2 and the secondary valency can also be 4.
So we can say that the primary and secondary valency of platinum in the complex is 2,6 and 2,4 .
Therefore, the correct answers are option (B) and option (D).
Note: In this type of questions, first we have to remember some basic points about the terms that are involved in the question. Then we will find out the primary and secondary valency by finding out the oxidation number and the coordination number of the compound in the complex and then we will check for some other possibilities. We will do the same for the possibilities of the given compound. Through this we will get our required answers of all the possibilities.