Which statement is true about simple molecular substances?

• A. They have low melting and boiling points
• B. They have high melting and boiling points
• C. They conduct electricity well as solids
• D. They form strong ionic lattices

Answer: (A)

Simple molecular substances are held together by weak intermolecular forces between molecules, not by strong bonds inside the molecules or between them. Because these forces are relatively weak, only a small amount of energy is needed to overcome them, so melting and boiling occur at low temperatures. They don’t conduct electricity well as solids because the molecules are neutral and there are no mobile ions or free electrons to carry charge. They also don’t form strong ionic lattices, since there isn’t a framework of ions held together by strong electrostatic forces. So, the statement that they have low melting and boiling points is the best description.