1. Intermolecular Forces: Sulfur exists as S8 rings in its elemental form, which are held together by covalent bonds. These covalent bonds are stronger than the intermolecular forces (van der Waals forces) present between chlorine molecules (Cl2). The stronger intermolecular forces in sulfur require more energy to overcome in order to melt the substance, resulting in a higher melting point.
2. Molecular Weight: The molecular weight of sulfur (S8) is 256.5 g/mol, while that of chlorine (Cl2) is 70.9 g/mol. The heavier molecular weight of sulfur means that more energy is required to break the bonds between its molecules, leading to a higher melting point.
3. Crystal Structure: In its solid state, sulfur forms an orthorhombic crystal structure, where the S8 rings pack efficiently and form a rigid lattice. On the other hand, chlorine forms a molecular crystal structure, where Cl2 molecules are held together by weak intermolecular forces. The more stable and rigid crystal structure of sulfur contributes to its higher melting point.
In summary, the stronger intermolecular forces, higher molecular weight, and more stable crystal structure of sulfur compared to chlorine result in a significantly higher melting point for sulfur (115.21°C) compared to chlorine (-101.5°C).
