Question

The valency of cuprammonium ion is:
A. +4
B. +2
C. -2
D. -4

Answer 1

Hint: In order to solve this question, we can proceed by first drawing its structure. The valency here is nothing but the oxidation state of the central metal ion. The structure of the compound is ${{[Cu{{(N{{H}_{3}})}_{4}}]}^{+2}}$. So we need to find the oxidation state of the copper atom.

Complete Step by Step Solution:
We can see ${{[Cu{{(N{{H}_{3}})}_{4}}]}^{+2}}$ is a coordination complex and we need to find its valency. In this case, we can say that the valency is nothing but the oxidation of the central metal atom to which the ligands are attached. The central metal atom in this case is Copper(Cu) and the ligand is $N{{H}_{3}}$.

The hypothetical charge that an atom would hold if all of its links to other atoms were entirely ionic in nature is what is known as an atom's oxidation state.

To proceed further let’s suppose the oxidation number of Cu to be x. And from the structure drawn we can see that the complex contains a net charge of +2. The ligand here is $N{{H}_{3}}$ which does not carry any charge that means, its charge is 0. So, we can conclude that the ligand will not play any role in determining the oxidation state of Cu.
So, the oxidation state or the valency of Cu in cuprammonium ion will be:
$x+4(0)=+2$
And thereby solving the above equation we get, $x=2$
Therefore, the correct option is B. +2 i.e. the valency of cuprammonium ion is +2.

Note: The thing to be noted here is that you should know how to form compounds or structures with the help of the given name of the compound. After this, you should know how to calculate the oxidation state of the complex compound.