What type of crystal defect is indicated in the diagram given below :
`{:(Na^(+),Cl^(-),Na^(+),Cl^(-),Na^(+),Cl^(-)),(Cl^(-),square,Cl^(-),Na^(+),square,Cl^(-)),(Na^(+),Cl^(-),square,Cl^(-),Na^(+),Cl^(-)),(Cl^(-),Na^(+),Cl^(-),Na^(+),square,N^(+)):}`

Options

A. Frenkel and Schotky defects
B. Schotky defect
C. Interstitial defect
D. Frenkel defect

Answer

To determine the type of crystal defect indicated in the given diagram, we will analyze the structure of NaCl and the nature of the defects.

### Step-by-Step Solution:

1. **Identify the Crystal Structure**:
- The question involves NaCl, which is an ionic compound. In the NaCl crystal structure, Na⁺ and Cl⁻ ions are arranged alternately in a cubic lattice.

**Hint**: Recall that NaCl has a face-centered cubic (FCC) structure with a 1:1 ratio of cations and anions.

2. **Examine the Diagram**:
- The diagram shows positions of Na⁺ and Cl⁻ ions, indicating some vacancies (empty squares) where either Na⁺ or Cl⁻ ions are missing.

**Hint**: Look for patterns in the vacancies. Are they equal in number for both Na⁺ and Cl⁻?

3. **Determine the Type of Defect**:
- In the diagram, both Na⁺ and Cl⁻ ions are missing in equal proportions. This suggests that there are vacancies for both types of ions.

**Hint**: Remember that a defect where equal numbers of cations and anions are missing is characteristic of a specific type of defect.

4. **Identify the Defect**:
- The absence of both Na⁺ and Cl⁻ ions in equal proportions indicates a Schottky defect. In a Schottky defect, vacancies are created for both cations and anions, maintaining overall charge neutrality.

**Hint**: Schottky defects are common in ionic compounds where the cations and anions are of similar sizes.

5. **Conclusion**:
- Based on the analysis, the type of crystal defect indicated in the diagram is a **Schottky defect**.

### Final Answer:
The type of crystal defect indicated in the diagram is a **Schottky defect** (Option B).