Which of the following specie(s) is/are having only one corner shared per tetrahedron.

Options

A. `Si_2O_7^(6-)`
B. `Cr_2O_7^(2-)`
C. `S_2O_7^(2-)`
D. `Si_3O_9^(6-)`

Answer

To determine which of the given species has only one corner shared per tetrahedron, we will analyze the structures of each species step by step.

### Step 1: Analyze Si2O7 6-
1. **Structure**: Si2O7 6- consists of two tetrahedral units. Each silicon atom is bonded to four oxygen atoms.
2. **3D Representation**: When visualized in 3D, the two tetrahedra share one corner (one oxygen atom).
3. **Conclusion**: Si2O7 6- shares only one corner between the two tetrahedra.

### Step 2: Analyze Cr2O7 2-
1. **Structure**: Cr2O7 2- (dichromate ion) also consists of two tetrahedral units.
2. **3D Representation**: In its 3D form, the two tetrahedra share one corner.
3. **Conclusion**: Cr2O7 2- shares only one corner between the two tetrahedra.

### Step 3: Analyze S2O7 2- (Pyrosulfate)
1. **Structure**: S2O7 2- consists of two tetrahedral units as well.
2. **3D Representation**: When viewed in 3D, these tetrahedra share one corner.
3. **Conclusion**: S2O7 2- shares only one corner between the two tetrahedra.

### Step 4: Analyze Si3O9 6-
1. **Structure**: Si3O9 6- is a trimer of sulfur trioxide and consists of three tetrahedral units.
2. **3D Representation**: In its 3D form, the central tetrahedron shares two corners with the other two tetrahedra.
3. **Conclusion**: Si3O9 6- does not meet the requirement as it shares two corners.

### Final Answer
The species that have only one corner shared per tetrahedron are:
- Si2O7 6-
- Cr2O7 2-
- S2O7 2-