Question

The large difference between the melting and boiling points of oxygen and sulphur may be explained on the basis of

• A. Atomic size
• B. Atomicity
• C. Electronegativity
• D. Electron gain enthalpy

Hint:

The atomicity of sulfur \( (S_8) \) results in stronger intermolecular forces compared to oxygen \( (O_2) \), leading to a higher melting and boiling point for sulfur.

Answer 1

The Correct Option is B

The substantial disparity in the melting and boiling points of oxygen (O₂) and sulfur (S₈) is principally attributed to their atomicity.

1. Atomicity: This term denotes the number of atoms comprising a molecule. Oxygen is found as a diatomic molecule (O₂), comprising two atoms. Conversely, sulfur commonly exists as an octatomic molecule (S₈), composed of eight atoms.
2. Intermolecular Forces: The S₈ molecular configuration of sulfur renders it larger and more intricate. This complexity leads to more robust van der Waals attractive forces between its molecules when juxtaposed with O₂. Overcoming these intensified forces necessitates greater energy input, resulting in elevated melting and boiling points for sulfur relative to oxygen.
3. Evaluation of Factors:
   • Atomic Size: While atomic size does influence melting and boiling points, the differential atomicity is the more dominant factor in this specific comparison.
   • Electronegativity: Electronegativity does not exert a direct impact on the melting or boiling points in this scenario.
   • Electron Gain Enthalpy: This property pertains to the energy shift upon electron addition to an atom and is unrelated to the determination of melting and boiling points.
4. Synopsis: The primary determinant for the significant difference in melting and boiling points between oxygen and sulfur is their respective atomicity. The distinct molecular structures (O₂ versus S₈) are responsible for variations in the strength of intermolecular forces, thereby influencing their phase transition temperatures.