The yellow colour of ZnO and Conducting nature produced on heating is due to

Options

A. Metal excess defects due to interstitial cation
B. Extra positive ions present in an interstitial site
C. Trapped electronsthat lie on anionic sites
D. All of these

Answer

To answer the question regarding the yellow color of ZnO and its conducting nature produced on heating, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Zinc Oxide (ZnO)**:
- Zinc oxide is a compound that can exhibit different colors depending on its state and conditions. In its pure form, ZnO is white.

2. **Heating of ZnO**:
- When ZnO is heated, it undergoes a change in its structure. The heating process causes some of the oxygen ions to leave their lattice sites, creating vacancies.

3. **Metallic Defect**:
- The absence of oxygen ions leads to a type of defect known as a "metal excess defect." In this defect, there are more metal ions (Zn²⁺) than there are anions (O²⁻) in the crystal lattice.

4. **Formation of F-Centers**:
- The vacancies left by the missing oxygen ions are filled by free electrons. These free electrons occupy the vacant sites, forming what are known as "F-centers." An F-center is a lattice vacancy that is occupied by one or more electrons.

5. **Color Change**:
- The presence of these F-centers is responsible for the yellow color of ZnO when heated. The trapped electrons can absorb certain wavelengths of light, leading to the appearance of yellow.

6. **Conducting Nature**:
- The free electrons that occupy the vacancies also contribute to the electrical conductivity of ZnO. When heated, the increased number of free electrons allows ZnO to conduct electricity.

7. **Conclusion**:
- Therefore, the yellow color of ZnO and its conducting nature upon heating are due to the formation of F-centers, which are created by the absence of oxygen ions and the presence of trapped electrons.

### Final Answer:
The yellow color of ZnO and its conducting nature produced on heating is due to the formation of F-centers, which are created by the absence of oxygen ions and the presence of trapped electrons.

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