Thortretite, `Sc_(2)Si_(2)O_(7)` is :

Options

A. a orthosilicate
B. a pyrosilicate
C. a sheet silicate
D. a cyclic silicate

Explanation

To determine the classification of Thortretite, \( \text{Sc}_2\text{Si}_2\text{O}_7 \), we will analyze its composition and compare it with known silicate structures.

### Step-by-Step Solution:

1. **Identify the Formula**: The compound in question is \( \text{Sc}_2\text{Si}_2\text{O}_7 \). This indicates that it contains scandium (Sc), silicon (Si), and oxygen (O).

2. **Determine the Basic Group**: In silicate chemistry, different types of silicates are characterized by their basic structural units:
- **Orthosilicates** have the unit \( \text{SiO}_4^{4-} \).
- **Pyrosilicates** have the unit \( \text{Si}_2\text{O}_7^{6-} \).
- **Sheet silicates** have the unit \( \text{Si}_2\text{O}_5^{2-} \) or similar.
- **Cyclic silicates** have units like \( \text{Si}_3\text{O}_9^{6-} \) or similar.

3. **Analyze the Composition of \( \text{Sc}_2\text{Si}_2\text{O}_7 \)**: The formula \( \text{Si}_2\text{O}_7 \) suggests that it contains the pyrosilicate unit \( \text{Si}_2\text{O}_7^{6-} \). This is because the presence of two silicon atoms and seven oxygen atoms corresponds to the pyrosilicate structure.

4. **Conclusion**: Since \( \text{Sc}_2\text{Si}_2\text{O}_7 \) contains the pyrosilicate unit \( \text{Si}_2\text{O}_7^{6-} \), we can conclude that Thortretite belongs to the category of **pyrosilicates**.

### Final Answer:
Thortretite, \( \text{Sc}_2\text{Si}_2\text{O}_7 \), is a **pyrosilicate**.

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