Different forms of carbon:

• Allotropes are different forms of the same element
• Small covalent molecules have low melting/boiling points due to weak intermolecular forces
• Giant covalent molecules are always solids at room temperature with high melting/boiling points because of millions of strong covalent bonds
• Diamond:

  • Made from carbon
  • Each carbon atom is joined to four other carbon atoms by strong covalent bonds
  • Cannot conduct electricity because electrons do not carry a charge
• Silicon dioxide:

  • Elements silicon and oxygen are covalently bonded
  • Has a high melting/boiling point due to many strong covalent bonds
• Graphite:

  • Made from carbon
  • Each carbon atom forms 3 covalent bonds with other carbon atoms
  • Hexagonal rings formed by carbon atoms
  • Soft and slippery due to layers with no covalent bonds allowing atoms to slide
  • Good conductor of heat and electricity due to delocalized electrons
• Graphene:

  • Single layer of graphite, one atom thick
  • Extremely strong
  • Good conductor of electricity due to delocalized electrons
• Fullerenes:

  • Molecules of carbon atoms with hollow shapes
  • Usually have hexagonal rings with rings of 5 or 7 carbon atoms
  • Used for catalysts to speed up chemical reactions
  • Lubricating properties to prevent moving parts from smashing together
• Carbon Nanotubes:

  • Fullerenes shaped into long cylinders
  • Can be stretched without breaking
  • Good conductor of heat and electricity