In `SiO_(2)`

Options

A. the coordination number of Si is 4 and that of O is 2
B. the coordination number of Si is 2 and that of O is 4
C. the coordination number Si and that of O are both 2
D. the coordination number of Si and that of O are both 4

Answer

To determine the coordination number of silicon (Si) and oxygen (O) in silicon dioxide (SiO₂), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Oxidation States**:
- In SiO₂, silicon (Si) has an oxidation state of +4, and oxygen (O) has an oxidation state of -2.

2. **Determine the Ratio of Atoms**:
- The formula SiO₂ indicates that for every 1 silicon atom, there are 2 oxygen atoms. Therefore, the ratio of silicon to oxygen is 1:2.

3. **Understanding Coordination Number**:
- The coordination number refers to the number of nearest neighbor atoms surrounding a central atom. In this case, we need to find how many oxygen atoms surround each silicon atom and how many silicon atoms surround each oxygen atom.

4. **Coordination of Silicon (Si)**:
- Each silicon atom (Si⁴⁺) is surrounded by 4 oxygen atoms (O²⁻). This is because silicon forms four bonds with the oxygen atoms in the tetrahedral arrangement. Therefore, the coordination number of silicon is 4.

5. **Coordination of Oxygen (O)**:
- Each oxygen atom (O²⁻) is shared between two silicon atoms. Since each oxygen atom is bonded to two silicon atoms, the coordination number of oxygen is 2.

6. **Conclusion**:
- The coordination number of silicon in SiO₂ is 4, and the coordination number of oxygen is 2.

### Final Answer:
- The coordination number of Si in SiO₂ is 4, and the coordination number of O is 2.