Questions & Answers

Question

Answers

A: $6$

B: $4$

C: $8$

D: $12$

Answer
Verified

We know coordination number is the number of atoms surrounding the central metal atom zinc blende has face centered cubic close packing. Since the number of atoms in a single unit cell of zinc and sulphur is the same it is consistent with the formula $ZnS$. Ionic radius of $Z{n^{2 + }}$ is $74pm$ and for ${S^{2 - }}$ is $190pm$ therefore the ratio between cationic and anionic radii in zinc blende is $0.39$ . This means zinc blends will possess a tetrahedral ion arrangement and there will be four nearest neighbors for both zinc and sulphur, this means coordination number of zinc and sulphur is$4$. So the answer to this question is B that is$4$ .

Additional information: Coordination number is also called ligancy. For molecules and polyatomic ions coordination number of an atom can be simply calculated by counting the number of atoms which are bound to that atom, it doesn’t matter if they are connected with single bond, double bond or triple bond. $ZnS$ Has unique structure as compared to other molecules. Zinc blende possess diamond type network but at different temperatures $ZnS$ can become the wurtzite structure type which has hexagonal symmetry but structure wise zinc blende is thermodynamically stable.

Wurtzite has (HCP) hexagonal close packing which is characterized by $12$ ions in the corners of each unit that create a hexagonal prism due to thermodynamic stability zinc blende slowly transforms to wurtzite.

Zinc extracted from zinc blende is used in many products such as batteries, making alloys, cosmetics, plastics, inks etc.

Zinc blende powder glows in dark so used in making toys, paint soap etc. which shows this property.

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