Diamond and silicon dioxide

• Giant covalent molecules


  Contain millions of covalent bonds
• Giant covalent substances are always solids at room temperature
• Diamond


  • Formed from the element carbon
  • Each carbon atom forms 4 covalent bonds to other carbon atoms
• Diamond contains millions of carbon atoms joined by covalent bonds
• Melting point of diamond

  Over 3,700 degrees C
• Diamond


  Cannot conduct electricity because all outer electrons are in covalent bonds, leaving no free electrons
• Silicon dioxide (silica)


  • Contains silicon and oxygen atoms covalently bonded together
  • Has a very high melting and boiling point for the same reason as diamond