Which of the following defect is seen in FeO

Options

A. Metal excess defect
B. Metal deficiency defect
C. Displacement defect
D. Impurity defect

Explanation

To determine which defect is seen in FeO (Iron(II) oxide), we will analyze the options provided and understand the characteristics of each defect type.

### Step-by-Step Solution:

1. **Understanding the Types of Defects**:
- **Schottky Defect**: This defect occurs when an equal number of cations and anions are missing from the lattice, maintaining electrical neutrality.
- **Frenkel Defect**: This defect occurs when an ion is displaced from its lattice site to an interstitial site, creating a vacancy at the original site.
- **Metal Deficiency Defect**: This defect occurs in compounds with variable valency metals, where there is a deficiency of metal ions to maintain charge balance.
- **Impurity Defect**: This defect occurs when foreign atoms are introduced into the lattice, which can disrupt the regular arrangement of ions.

2. **Analyzing FeO**:
- FeO is composed of iron (Fe) and oxygen (O). Iron can exhibit variable valency, typically +2 and +3.
- In FeO, iron is in the +2 oxidation state. However, due to the presence of variable valency, there can be instances where some iron ions are missing to maintain charge neutrality.

3. **Identifying the Defect**:
- Given that FeO has iron in a variable oxidation state, it is likely to exhibit a **metal deficiency defect**. This is because, to maintain the overall charge balance in the crystal lattice, some Fe²⁺ ions may be missing.

4. **Conclusion**:
- The defect seen in FeO is a **metal deficiency defect**.

### Final Answer:
The defect seen in FeO is a **metal deficiency defect**.