Question

The correct statement regarding defects in solid is

• A. Frenkel defect is a vacancy defect
• B. Schottky defect is a dislocation defect
• C. Trapping of an electron in the lattice leads to the formation of F-centre
• D. Schottky defect has no effect on density

Answer 1

The Correct Option is C

Let's evaluate each statement regarding defects in solids:

Frenkel defect is a vacancy defect:

• This statement is incorrect. A Frenkel defect is a type of point defect where an ion is displaced from its normal position to an interstitial site, creating a vacancy and an interstitial defect. It involves both a vacancy and an interstitial, not just a vacancy.

Schottky defect is a dislocation defect:

• This statement is incorrect. A Schottky defect is a point defect where a pair of ions (typically cations and anions) are missing from the crystal lattice, leading to vacancies. It is not a dislocation defect.

Trapping of an electron in the lattice leads to the formation of F-centre:

• This statement is correct. An F-centre is a point defect where an electron is trapped in a vacancy within the lattice, causing the lattice to absorb light and give a characteristic color. This occurs due to the presence of trapped electrons.

Schottky defect has no effect on density:

• This statement is incorrect. A Schottky defect causes a loss of ions (both cations and anions), which leads to a decrease in the density of the material.

The correct answer is (C) : Trapping of an electron in the lattice leads to the formation of F-centre.

Answer 2

1. Frenkel defect is a vacancy defect

- Incorrect: A Frenkel defect involves a displacement of an ion from its normal lattice position to an interstitial site. While it creates a vacancy and an interstitial defect, it is not purely a vacancy defect.

2. Schottky defect is a dislocation defect

- Incorrect: A Schottky defect occurs when an equal number of cations and anions are missing from their lattice sites, creating vacancies. It is not related to dislocations, which are defects involving misalignments in the regular arrangement of atoms.

3. Trapping of an electron in the lattice leads to the formation of F-centre

- Correct: The F-centre is formed when an electron is trapped in a vacancy (usually an anion vacancy) in the crystal lattice. The trapped electron contributes to the color of the crystal. This is a true statement.

4. Schottky defect has no effect on density

- Incorrect: A Schottky defect involves missing ions, which leads to a decrease in the density of the solid because the number of particles in the crystal decreases.

Final Answer: The correct statement is: Trapping of an electron in the lattice leads to the formation of F-centre.