The co-ordination number of calcium fluoride `(CaF_(2))` type structure is

Options

A. `1 : 2`
B. `4 : 4`
C. `4 : 8`
D. `8 : 4`

Explanation

To determine the coordination number of calcium fluoride (CaF₂), we can follow these steps:

### Step 1: Understand the Structure of CaF₂
Calcium fluoride has a specific crystal structure known as the fluoride structure. In this structure, the calcium ions (Ca²⁺) occupy the face-centered cubic (FCC) lattice positions, while the fluoride ions (F⁻) occupy the tetrahedral voids within the lattice.

**Hint**: Remember that the arrangement of ions in a crystal structure is crucial for determining coordination numbers.

### Step 2: Identify the Cation and Anion
In CaF₂, the cation is calcium (Ca²⁺) and the anion is fluoride (F⁻). The coordination number refers to the number of nearest neighbor ions surrounding a given ion.

**Hint**: Identify which ions are cations and which are anions to understand their roles in the structure.

### Step 3: Determine the Coordination Number of Calcium
Each calcium ion (Ca²⁺) is surrounded by 8 fluoride ions (F⁻). This means that the coordination number for calcium in CaF₂ is 8.

**Hint**: Visualize the arrangement of ions to see how many anions surround each cation.

### Step 4: Determine the Coordination Number of Fluoride
Each fluoride ion (F⁻) is surrounded by 4 calcium ions (Ca²⁺). Therefore, the coordination number for fluoride in CaF₂ is 4.

**Hint**: Look at how many cations surround each anion to find its coordination number.

### Step 5: Conclusion
The coordination numbers for calcium fluoride (CaF₂) can be summarized as follows:
- Coordination number of Ca²⁺ = 8
- Coordination number of F⁻ = 4

Thus, the overall coordination number ratio for CaF₂ is 8:4.

**Final Answer**: The coordination number of calcium fluoride (CaF₂) type structure is 8 for calcium and 4 for fluoride.