In the calcum fluaride structure, the coordination bumber of the cations and anions are respectively ,

Options

A. 6 and 6
B. 8 and 4
C. 4 and 4
D. 4 and 8

Explanation

To determine the coordination numbers of cations and anions in the calcium fluoride (CaF2) structure, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Ions in Calcium Fluoride**:
- Calcium fluoride consists of calcium ions (Ca²⁺) and fluoride ions (F⁻).

2. **Understand the Crystal Structure**:
- The structure of calcium fluoride is known as the fluorite structure. In this structure, calcium ions occupy the face-centered cubic (FCC) lattice positions.

3. **Determine the Position of Ions**:
- In the fluorite structure, the calcium ions (Ca²⁺) are located at the corners and the face centers of the cubic unit cell.
- The fluoride ions (F⁻) occupy the tetrahedral voids in this structure.

4. **Calculate the Coordination Number of Calcium Ions**:
- Each calcium ion is surrounded by 8 fluoride ions in the fluorite structure. Therefore, the coordination number of Ca²⁺ is 8.

5. **Calculate the Coordination Number of Fluoride Ions**:
- Each fluoride ion is surrounded by 4 calcium ions. Thus, the coordination number of F⁻ is 4.

6. **Summarize the Coordination Numbers**:
- The coordination number of cations (Ca²⁺) is 8, and the coordination number of anions (F⁻) is 4.

### Final Answer:
The coordination numbers of the cations and anions in calcium fluoride (CaF2) are respectively 8 and 4.

---