Large difference between the melting and boiling points of oxygen and sulphur can be explained.

Options

A. one the basis of their molecular weight
B. one the basis of their atomicity
C. (1) and (2) both
D. None

Answer

To explain the large difference between the melting and boiling points of oxygen and sulfur, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Melting and Boiling Points**:
- The melting point of oxygen (O₂) is -218°C, and its boiling point is -183°C.
- The melting point of sulfur (S₈) is 115°C, and its boiling point is 445°C.

2. **Understand the Molecular Composition**:
- Oxygen exists as a diatomic molecule (O₂), meaning each molecule consists of two oxygen atoms.
- Sulfur exists as an octatomic molecule (S₈), meaning each molecule consists of eight sulfur atoms.

3. **Compare Molecular Weights**:
- The molecular weight of O₂ is 32 g/mol (16 g/mol per oxygen atom × 2).
- The molecular weight of S₈ is 256 g/mol (32 g/mol per sulfur atom × 8).

4. **Analyze the Impact of Atomicity**:
- The atomicity of oxygen is 2 (O₂), while the atomicity of sulfur is 8 (S₈). Higher atomicity in sulfur leads to stronger intermolecular forces.

5. **Discuss Van der Waals Forces**:
- Van der Waals forces are weak intermolecular forces that increase with molecular weight and size.
- Since sulfur has a higher molecular weight and more atoms, it experiences stronger Van der Waals forces compared to oxygen.

6. **Conclude the Differences in Melting and Boiling Points**:
- Due to the higher molecular weight and stronger Van der Waals forces in sulfur, both its melting and boiling points are significantly higher than those of oxygen.

### Final Conclusion:
The large difference in melting and boiling points between oxygen and sulfur can be attributed to the higher molecular weight and atomicity of sulfur, which leads to stronger intermolecular forces (Van der Waals forces) compared to those in oxygen.