Question

Which of the following has the Frenkel defect?
A. Sodium chloride
B. Graphite
C. Silver bromide
D. Diamond

Answer 1

Hint: Frenkel defect or dislocation defect is a type of point defect in crystalline solids named after its discoverer Yakov Frenkel. Frenkel defect is exhibited in ionic compounds in which the radius ratio is low. Now, check which option has these qualities.

Complete answer:
So, let us understand what Frenkel defect is:
Yakov Frenkel, a Russian physicist was the person who discovered the Frenkel defect while conducting research on the molecular theory of condensed state. However, this discovery was important as his model explained a defect in the molecule of crystalline solids where an atom or ion moved out of their own lattice site making it vacant while occupying another intermediary vacant site on the same crystal. The defect is also known as dislocation defect and it also clearly depicts both vacancy and self-interstitial defects.
The Frenkel defect is another form of a point defect which is created when an atom or cation leaves its original place in the lattice structure to create a vacancy while occupying another interstitial position within the solid crystal.

Let us now see a few characteristics of Frenkel defect:
This defect occurs only when cations are smaller in size when compared to the anions. There are also no changes in chemical properties. There is also no significant impact of Frenkel defect on the density of the solid and therefore both the volume and mass of the solid is preserved. In such cases, substances also maintain their electrical neutrality.
The examples of this defect are: ZnS, AgCl, AgBr and AgI.
So, from the above information we can conclude that silver bromide shows Frenkel defect.

Therefore, option C is the required answer.

Note: Schottky defect occurs in those ionic crystals where the difference in size between cation and anion is small. Remember that AgBr shows both the defects.