diamond and silicone dioxide

• Giant covalent molecules


  Contain millions of covalent bonds
• Giant covalent substances are always solids at room temperature
• Giant covalent substances have high melting and boiling points
• Diamond


  • Formed from the element carbon
  • Each carbon atom forms covalent bonds to four other carbon atoms
• Representing diamond


  1. Carbon atoms shown as circles

  2. Covalent bonds shown as sticks
• Even a tiny diamond contains millions and millions of carbon atoms joined by covalent bonds
• Melting point of diamond

  Over 3,700 degrees C
• Diamond cannot conduct electricity
• Silicon dioxide (silica)


  • Contains the elements silicon and oxygen covalently bonded together
• Silicon dioxide has a very high melting and boiling point
• To melt silicon dioxide, the covalent bonds must be broken, which takes a great deal of energy