In normal spinel structure there is a closed packed array of `O^(2-)` ions. The trivalent cations are present in

Options

A. 75 % of octahedral voids
B. 50 % of octachedral voids
C. 12.5 % of tetrahedral voids
D. 25 % of octahedral voids

Answer

To solve the question regarding the presence of trivalent cations in the normal spinel structure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure**: In a normal spinel structure, we have a close-packed arrangement of oxide ions (O²⁻). The cations present in the structure are typically divalent (A²⁺) and trivalent (B³⁺).

2. **Identify the Cation Positions**: In the normal spinel structure:
- The divalent cations (A²⁺) occupy tetrahedral voids.
- The trivalent cations (B³⁺) occupy octahedral voids.

3. **Determine the Occupancy of Cations**:
- It is known that in the normal spinel structure, the trivalent cations occupy **50% of the octahedral voids**.

4. **Analyze the Options**: The question provides four options regarding the occupancy of the trivalent cations:
- 75% of octahedral voids
- 50% of octahedral voids
- 12.5% of tetrahedral voids
- 25% of octahedral voids

5. **Select the Correct Answer**: Since we established that trivalent cations occupy 50% of the octahedral voids, the correct answer is:
- **50% of octahedral voids** (Option 2).

### Final Answer:
The trivalent cations are present in **50% of octahedral voids** in the normal spinel structure.

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