The example of an orthosilicate is:

Options

A. `MgCaSi_(2)O_(6)`
B. `Mg_(2)SiO_(4)`
C. `Fe_(2)O_(3)SiO_(2)`
D. ` Be_(3)Al_(2)Si_(6)O_(8)`

Answer

To solve the question, "The example of an orthosilicate is:", we need to identify which of the given options represents an orthosilicate based on the definition and structure of orthosilicates.

### Step-by-step Solution:

1. **Understand Orthosilicates**:
- Orthosilicates are silicates that contain isolated silicate anions. The basic unit of an orthosilicate is the tetrahedral silicate ion, represented as \( \text{SiO}_4^{4-} \).

2. **Identify the Characteristics of Orthosilicates**:
- An orthosilicate will have the formula that includes the \( \text{SiO}_4^{4-} \) unit. This means that in the formula of the compound, we should see this unit without any additional silicate units or polymerization.

3. **Examine the Options**:
- Let's analyze the options provided (though they are not explicitly listed in the question, we will assume common examples):
- **Option 1**: \( \text{Si}_2\text{O}_6 \) - This contains two silicate units and is not an orthosilicate.
- **Option 2**: \( \text{Mg}_2\text{SiO}_4 \) - This contains the \( \text{SiO}_4^{4-} \) unit and is indeed an orthosilicate.
- **Option 3**: \( \text{SiO}_2 \) - This is a network silicate and does not represent an orthosilicate.
- **Option 4**: \( \text{Si}_6\text{O}_8 \) - This also contains multiple silicate units and is not an orthosilicate.

4. **Conclusion**:
- Based on the analysis, the only option that represents an orthosilicate is **Option 2: \( \text{Mg}_2\text{SiO}_4 \)**.

### Final Answer:
The example of an orthosilicate is **\( \text{Mg}_2\text{SiO}_4 \)**.

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