Question

Which of the following is not correct for Frenkel defect?

• A. It doesn't change the density of the solid
• B. It is also called dislocation point defect
• C. Entropy of the solid increases
• D. It is due to very small difference in the size of ions

Hint:

Frenkel defects occur when smaller ions, like cations, move to interstitial sites, creating vacancies, typically in ionic solids with a large size difference between the ions.

Answer 1

The Correct Option is D

- The Frenkel defect occurs when an ion is displaced from its normal position in the crystal lattice and occupies an interstitial site, creating a vacancy and an interstitial defect. This does not affect the density of the solid, so option (1) is correct.
- The Frenkel defect is also known as a dislocation point defect because it involves the movement of ions from their regular positions, so option (2) is correct.
- The entropy of the solid increases because the ions are displaced from their original positions, thus increasing the disorder in the system, so option (3) is correct.
- However, the Frenkel defect occurs when there is a large difference in the size of ions, typically between a cation and an anion, not a very small difference, making option (4) incorrect.