Which of the following statement regarding defects in solids is/are correct?

Options

A. Schottky defect has no effect on the physical properties of solids
B. Frenkel defect is a dislocation defect
C. Frenkel defect is usually favoured by a very small difference in the sizes of cation and anions
D. Trapping of proton in the lattice leads to the formation of F-centres.

Explanation

To determine which statements regarding defects in solids are correct, we need to analyze each option provided in the question. Let's break down the statements one by one.

### Step-by-Step Solution:

1. **Evaluate the First Statement:**
- **Statement:** Schottky defect has no effect on the physical properties of solids.
- **Analysis:** This statement is incorrect. Schottky defects occur when equal numbers of cations and anions are missing from the lattice, which decreases the mass of the crystalline solid and thus affects its density. The presence of vacancies can also influence electrical conductivity.
- **Conclusion:** This statement is **false**.

2. **Evaluate the Second Statement:**
- **Statement:** Frenkel defect is the dislocation defect.
- **Analysis:** This statement is correct. In a Frenkel defect, a smaller cation is displaced from its lattice position to an interstitial site, creating a vacancy and an interstitial defect. This is indeed a type of dislocation defect.
- **Conclusion:** This statement is **true**.

3. **Evaluate the Third Statement:**
- **Statement:** Frenkel defect is usually favored by a small difference between the size of cations and anions.
- **Analysis:** This statement is incorrect. Frenkel defects typically occur when there is a significant size difference between cations and anions, allowing the smaller cation to fit into an interstitial site. Therefore, a small size difference is not favorable for the formation of Frenkel defects.
- **Conclusion:** This statement is **false**.

4. **Evaluate the Fourth Statement:**
- **Statement:** Trapping of protons in the lattice leads to the formation of F center.
- **Analysis:** This statement is incorrect. F centers are formed when electrons are trapped in the lattice of a crystalline solid, not protons. The presence of trapped electrons creates color centers in the material.
- **Conclusion:** This statement is **false**.

### Final Answer:
Based on the analysis, the only correct statement is the second one. Therefore, the correct answer is:

**Option B: Only the second statement is correct.**