Schottky defect is noticed in-

Options

A. NaCl
B. KCl
C. CsCl
D. All

Answer

To answer the question regarding where Schottky defects are noticed, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Schottky Defect**:
- A Schottky defect occurs in ionic crystals when an equal number of cations and anions are missing from the lattice, creating vacancies. This defect maintains the overall charge neutrality of the crystal.

2. **Identify Characteristics of Schottky Defect**:
- It is typically observed in ionic compounds.
- The size of cations and anions must be comparable for Schottky defects to occur.

3. **Analyze the Given Options**:
- The options provided are NaCl, KCl, CsCl, and "All of the above".

4. **Check Each Compound**:
- **NaCl**: Sodium chloride has comparable sizes of Na⁺ and Cl⁻ ions, making it suitable for Schottky defects.
- **KCl**: Potassium chloride also has comparable sizes of K⁺ and Cl⁻ ions, thus it can exhibit Schottky defects.
- **CsCl**: Cesium chloride similarly has comparable sizes of Cs⁺ and Cl⁻ ions, allowing for Schottky defects.

5. **Conclusion**:
- Since all three compounds (NaCl, KCl, and CsCl) can exhibit Schottky defects due to the comparable sizes of their ions, the correct answer is "All of the above".

### Final Answer:
**Schottky defect is noticed in: All of the above (NaCl, KCl, CsCl)**.

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