Why does silicon dioxide have a high boiling point?

• A. The strong covalent bonds take a lot of energy to break
• B. Weak intermolecular forces
• C. Low molecular mass
• D. Ionic bonds

Answer: (A)

Silicon dioxide has a high boiling point because it forms a giant covalent network. In this structure every silicon atom is covalently bonded to four oxygens and each oxygen connects to other silicon atoms, creating a vast 3D lattice of strong covalent bonds. To boil it, you’d have to break many of these bonds across the entire network, which requires a lot of energy. It’s not about weak intermolecular forces or a low molecular mass, since there aren’t discrete molecules held together by such forces here, and it isn’t ionic bonding.