`CO_(2)` is a gas while `SiO_(2)` is a solid. Explain.

Answer

To explain why \( CO_2 \) is a gas while \( SiO_2 \) is a solid at room temperature, we can break down the reasoning into several steps:

### Step 1: Understand the Elements
- **Carbon (C)** and **Silicon (Si)** are both in Group 14 of the periodic table. Carbon is the first member, while Silicon is the second member of this group.

### Step 2: Compare Atomic Sizes
- As we move down the group in the periodic table, the size of the atoms increases. Therefore, Silicon has a larger atomic size than Carbon.

### Step 3: Electronegativity Considerations
- Electronegativity tends to decrease as we go down a group. Carbon has a higher electronegativity compared to Silicon. This difference affects the types of bonds that can be formed.

### Step 4: Bonding in \( SiO_2 \)
- Silicon in \( SiO_2 \) forms four single covalent bonds with oxygen. The large size of Silicon prevents it from forming effective pi bonds (P-Pi P-Pi bonding), which are important for creating multiple bonds.

### Step 5: Structure of \( SiO_2 \)
- The bonding in \( SiO_2 \) leads to a three-dimensional (3D) network structure, similar to that of diamond. This structure is very strong and requires a significant amount of energy to break the bonds, making \( SiO_2 \) a solid at room temperature.

### Step 6: Bonding in \( CO_2 \)
- In contrast, Carbon in \( CO_2 \) can form double bonds with oxygen due to its smaller size and higher electronegativity. This allows for effective P-Pi P-Pi bonding.

### Step 7: Molecular Structure of \( CO_2 \)
- \( CO_2 \) has a linear molecular structure with weak Van der Waals interactions between the molecules. The weak interactions mean that very little energy is required to separate the molecules.

### Step 8: Conclusion
- Because \( CO_2 \) has weak intermolecular forces and requires less energy to break the bonds, it exists as a gas at room temperature. On the other hand, \( SiO_2 \) has a strong 3D network structure that makes it a solid at room temperature.

### Summary
- \( CO_2 \) is a gas due to weak intermolecular forces and the ability to form double bonds, while \( SiO_2 \) is a solid due to its strong 3D network structure and the nature of bonding.

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