which of the following point defects are shoen by AgBr (s) crystals ?
(a) Schottky defect
(b) Frenkel defect
( c) metal ecxess defect
(d) Metal deficiency defect

Options

A. 1 and 2
B. 3 and 4
C. 1and 3
D. 2 and 4

Explanation

To determine which point defects are shown by AgBr (silver bromide) crystals, we need to analyze the types of defects mentioned in the question: Schottky defect, Frenkel defect, metal excess defect, and metal deficiency defect.

### Step-by-Step Solution:

1. **Understanding Point Defects**:
- Point defects are imperfections in the crystal structure that occur at a single lattice point. They can be classified into different types, including Schottky defects and Frenkel defects.

2. **Schottky Defect**:
- A Schottky defect occurs when an equal number of cations and anions are missing from the lattice, creating vacancies. This defect is common in ionic solids where the size of cations and anions is similar.
- In AgBr, the cation (Ag⁺) and anion (Br⁻) are of similar size, which allows for the formation of Schottky defects.

3. **Frenkel Defect**:
- A Frenkel defect occurs when an ion (usually a cation) is displaced from its lattice site to an interstitial site, creating a vacancy and an interstitial defect.
- AgBr can also exhibit Frenkel defects due to the relatively small size of Ag⁺ ions, allowing them to occupy interstitial sites.

4. **Metal Excess Defect**:
- Metal excess defects occur when there are extra metal cations in the lattice, typically due to the presence of anionic vacancies.
- AgBr does not typically show metal excess defects because it maintains a stoichiometric ratio of Ag⁺ and Br⁻ ions.

5. **Metal Deficiency Defect**:
- Metal deficiency defects occur when there are fewer metal cations than expected in the lattice structure.
- AgBr does not exhibit metal deficiency defects as it maintains its stoichiometry.

6. **Conclusion**:
- Based on the analysis, AgBr crystals exhibit both Schottky and Frenkel defects. Therefore, the correct options are (a) Schottky defect and (b) Frenkel defect.

### Final Answer:
The point defects shown by AgBr (s) crystals are:
- (a) Schottky defect
- (b) Frenkel defect