Pyro-silicates are formed by

Options

A. ` SiO_4^(4-)` tetrahedra
B. `(Si_2O_7^(6-))`
C. `(Si_O_3^(2-))`
D. `(Si_2O_5^(12-))`

Answer

To answer the question "Pyro-silicates are formed by," we need to understand the composition and structure of pyro-silicates.

### Step-by-Step Solution:

1. **Understanding Pyro-silicates**:
- Pyro-silicates are a type of silicate mineral that contain silicon and oxygen in a specific arrangement. They are characterized by the presence of tetrahedral units.

2. **Tetrahedral Units**:
- The basic building block of silicates is the tetrahedron, which consists of a silicon atom (Si) surrounded by four oxygen atoms (O). In pyro-silicates, these tetrahedra are linked together.

3. **Formation of Pyro-silicates**:
- In pyro-silicates, two tetrahedra share one oxygen atom. This sharing creates a structure that can be represented as Si2O7. Each tetrahedron has a charge of -4, and when two tetrahedra share an oxygen, the overall charge becomes -6.

4. **Chemical Formula**:
- The chemical formula for pyro-silicates can be represented as Si2O7^6-. This indicates that the structure consists of two silicon atoms and seven oxygen atoms, with a total charge of -6.

5. **Conclusion**:
- Therefore, pyro-silicates are formed by the combination of tetrahedral units of silicon and oxygen, specifically represented by the formula Si2O7^6-.

### Final Answer:
Pyro-silicates are formed by Si2O7^6-.

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