Identifying simple molecular structure by low melting point and poor conductivity

Steps:

• Recall simple molecular structures have low melting points due to weak forces between molecules, are insoluble in water, and show poor electrical conductivity without free ions or electrons.
• Examine melting points: low (around 100°C or less) indicates simple molecular; high suggests metallic, ionic, or giant structures.
• Check solubility: simple molecular substances are typically insoluble in water.
• Verify conductivity: always poor for simple molecular, unlike metals (good in solid) or ionic (good when molten/dissolved).

Why B is correct:

• Melting point of 113°C is low, indicating weak intermolecular forces typical of simple molecular structures like iodine, with insolubility and always poor conductivity confirming no mobile charges.

Why the others are wrong:

• A: Reacts with water, characteristic of reactive ionic compounds like sodium.
• C: Good conductivity when solid, typical of metallic structures with delocalized electrons.
• D: High melting point of 1600°C indicates strong bonds in giant molecular (e.g., diamond) or ionic lattices.

Final answer: B