Explanation:



Zinc sulfide (ZnS) shows Frenkel defect as it involves the movement of a cation from its normal lattice site to an interstitial position, creating a vacancy at its original site. The cation in ZnS is Zn, which is smaller than the anion S. The smaller size of the cation allows it to move into the interstitial site without disturbing the overall crystal structure. This creates a vacancy at its original site, which is compensated by the formation of a pair of interstitial Zn and S ions. Thus, Frenkel defect is shown by ZnS.

Types of Stoichiometric Defects:


There are two types of stoichiometric defects, which are as follows:

1. Schottky Defect:


Schottky defect arises when equal numbers of cations and anions are missing from their normal lattice sites in the ionic crystal. It creates a pair of vacancies, one each on the cation and anion sites. Schottky defects are found in ionic compounds with high coordination numbers, such as NaCl, KCl, and CsCl.

2. Frenkel Defect:


Frenkel defect arises when a cation is displaced from its normal lattice site to an interstitial site, creating a vacancy at its original site. Frenkel defect is commonly found in ionic compounds with low coordination numbers, such as AgCl, ZnS, and Cu2O. Frenkel defects do not affect the density of the crystal because the displaced cation still remains within the crystal.

Conclusion:


In conclusion, ZnS shows Frenkel defect, which is a type of stoichiometric defect. Frenkel defect arises when a cation is displaced from its normal lattice site to an interstitial site, creating a vacancy at its original site.