Which of the following defects doesn't disturb stoichiometry of solid ?

Options

A. Schottky defect
B. metal excess defect
C. Non-stoichiometric defects
D. Frenkel defect

Answer

To solve the question "Which of the following defects doesn't disturb stoichiometry of solid?", we will analyze each option provided and identify which defects are stoichiometric and do not disturb the stoichiometry of a solid.

### Step-by-Step Solution:

1. **Understanding Point Defects**:
- Point defects are imperfections in the crystal lattice that occur at a single lattice point. They can be classified into three main categories: stoichiometric defects, non-stoichiometric defects, and impurity defects.

**Hint**: Recall the definition of point defects and their classifications.

2. **Identifying Stoichiometric Defects**:
- Stoichiometric defects do not alter the overall composition of the solid. They maintain the ratio of the constituent elements. The two main types of stoichiometric defects are:
- **Schottky defect**: This occurs when equal numbers of cations and anions are missing from the lattice, maintaining the stoichiometry.
- **Frenkel defect**: This occurs when an ion is displaced from its lattice site to an interstitial site, but the overall charge balance remains unchanged.

**Hint**: Focus on the definitions of Schottky and Frenkel defects.

3. **Analyzing the Given Options**:
- **Option 1: Schottky defect** - This defect does not disturb stoichiometry as it maintains the ratio of cations to anions.
- **Option 2: Metal excess defect** - This is a non-stoichiometric defect where there is an excess of metal ions, disturbing the stoichiometry.
- **Option 3: Non-stoichiometric defect** - By definition, these defects disturb the stoichiometry of the solid.
- **Option 4: Frenkel defect** - This defect also does not disturb stoichiometry as it involves the displacement of ions without changing the overall composition.

**Hint**: Compare each option against the definitions of stoichiometric and non-stoichiometric defects.

4. **Conclusion**:
- The defects that do not disturb the stoichiometry of a solid are the **Schottky defect** and the **Frenkel defect**. Therefore, the correct options are:
- **Option 1: Schottky defect**
- **Option 4: Frenkel defect**

**Hint**: Summarize the findings to arrive at the final answer.

### Final Answer:
The defects that do not disturb the stoichiometry of a solid are:
- **Schottky defect (Option 1)**
- **Frenkel defect (Option 4)**