For tetrahedral co-ordination the radius ratio `(r^(+) //r^(-))`should be

Options

A. `0.414 - 0.732`
B. `gt 0.732`
C. 0.156 - 0.225
D. 0.225 - 0.414

Answer

To determine the radius ratio for tetrahedral coordination, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Coordination Number**:
- The coordination number refers to the number of atoms or ions immediately surrounding a central atom in a complex or crystal structure. For tetrahedral coordination, the coordination number is 4.

2. **Identify Radius Ratio**:
- The radius ratio is defined as the ratio of the radius of the cation (r⁺) to the radius of the anion (r⁻). This ratio helps in predicting the type of coordination geometry that will be formed.

3. **Refer to Radius Ratio Ranges**:
- Different coordination numbers have specific ranges for their radius ratios. We can summarize these as follows:
- Coordination number 2: Radius ratio (r⁺/r⁻) = 0 to 0.155
- Coordination number 3: Radius ratio (r⁺/r⁻) = 0.155 to 0.225
- Coordination number 4 (Tetrahedral): Radius ratio (r⁺/r⁻) = 0.225 to 0.414
- Coordination number 6: Radius ratio (r⁺/r⁻) = 0.414 to 0.732
- Coordination number 8: Radius ratio (r⁺/r⁻) = 0.732 to 1

4. **Determine the Range for Tetrahedral Coordination**:
- Since tetrahedral coordination has a coordination number of 4, we can conclude that the radius ratio for tetrahedral coordination is between 0.225 and 0.414.

5. **Conclude the Answer**:
- Therefore, the radius ratio (r⁺/r⁻) for tetrahedral coordination is in the range of **0.225 to 0.414**.