Which of the following contains rock salt structure?

Options

A. `SrF_(2)`
B. MgO
C. `AI_(2)O_(3)`
D. All of these

Answer

To determine which of the given options contains a rock salt structure, we need to analyze the characteristics of the rock salt structure and apply them to the options provided.

### Step-by-Step Solution:

1. **Understand the Rock Salt Structure**:
- The rock salt structure is characterized by a face-centered cubic (FCC) arrangement of anions (usually larger) and octahedral coordination of cations (usually smaller).
- The ratio of the radius of cation (R+) to the radius of anion (R-) should lie between 0.414 and 0.732.

2. **Identify the Cation and Anion**:
- For the rock salt structure, we typically look for compounds that consist of a cation and an anion. Common examples include NaCl, MgO, and others.

3. **Calculate the Radius Ratio**:
- For the compound in question (let’s take MgO as an example), we need to find the ionic radii of the cation (Mg²⁺) and the anion (O²⁻).
- The ionic radius of Mg²⁺ is approximately 0.072 nm, and the ionic radius of O²⁻ is approximately 0.140 nm.

4. **Compute the Radius Ratio**:
- The radius ratio (R+/R-) = (Radius of Mg²⁺) / (Radius of O²⁻) = 0.072 nm / 0.140 nm ≈ 0.514.
- Since 0.514 lies between 0.414 and 0.732, MgO exhibits a rock salt structure.

5. **Conclusion**:
- Based on the above calculations, we conclude that MgO contains a rock salt structure. If there are other options provided, you would perform similar calculations for each to determine if they also fall within the required radius ratio.

### Final Answer:
- The compound that contains a rock salt structure is **MgO**.