Question

What is the coordination number of Copper in ${{[Cu{{(N{{H}_{3}})}_{4}}]}^{2+}}$?

Answer 1

Hint: To find the coordination number of an atom we must see the number of ions or molecules attached to the central atom. The central atom in this coordination compound is copper. The complex given is the cation as it has gained a positive charge.

Complete answer:
The coordination number of a compound is defined as the number of ions, atoms, or molecules attached to the central atom in the complex. The ions attached to the central atom are termed ligands. Thus the coordination number of an atom is also referred to as Ligancy.
Now let us understand- How to calculate the coordination number of a complex.
Step 1- Identify the central atom in the complex. Usually, the central atoll is a transition metal.
Step 2- Identify the ligands (ion/molecule/atom) in the complex that are attached to a central atom. They are generally present beside the central atom in the chemical formula.
Step 3- if there is more than one ligand, add all the atoms/ions of the molecule.
Step 4- Calculate the total number of atoms and the bonds between them.
In ${{[Cu{{(N{{H}_{3}})}_{4}}]}^{2+}}$, Cu is the central atom. There are 4 Amino groups bonded to the Cu atom.
IUPAC name of ${{[Cu{{(N{{H}_{3}})}_{4}}]}^{2+}}$is Tetra amine copper (II) ion.
The ligand is an amine that is $N{{H}_{3}}$ group and tetra means four in coordination compounds.
Thus, the Coordination number of Copper (Cu) ${{[Cu{{(N{{H}_{3}})}_{4}}]}^{2+}}$is 4.
The geometry of the compound is dependent on the coordination number. Here, as the CN is 4- the geometry will be tetrahedral or square planar.

Note:
 The Coordination number is attached to the central atom. The minimum coordination number is 2 and the maximum can be 16. Do not make the mistake of counting the number of bonds to determine the nature of the compound.