In zinc blende (ZnS) structure, the coordination number of \[Z{n^{2 + }}\] ion is:

Hint: In order to find out the coordination number of an ion in a compound, we need to observe its charge carefully. Coordination number, also referred to as Ligancy, is the number of atoms, ions, or molecules that a central atom or ion holds as its nearest neighbours in a complex or coordination compound or in a crystal.

Complete Step by Step Solution:
According to the question, we are given the compound ZnS which \[Z{n^{2 + }}\] as it is clearly mentioned has a positive charge hence it is a cation, and \[{S^{2 - }}\] being negatively charged is an anion.

As we know cations are occupied in the voids and anions are present in the spheres of the geometry of the compound.

In zinc blende (ZnS), the sulphide ions are anions and are centre-faced.
It means it has a coordination number 4 while zinc is cation ions that are present in the tetrahedral voids which alternate.

We know that the coordination number of zinc is 4 and the sulphide ion in ZnS is face-centred so its coordination number is also 4.
Hence, the radius ratio rate of the cation to that of anion is 4:4 \[Z{n^{2 + }}\] .

Note:The compound Zinc sulphide can be described as the organic compound with the chemical formula ZnS. It mainly occurs as a mineral but ZnS is the main compound form of zinc in nature. Although the mineral is usually black because of various impurities, the pure material is of white colour, and it is widely used as a pigment.