Metals and Special Materials

• Graphene

  . Graphene is a form of carbon. It is a single layer of graphite and is used in electronics and to make composite materials (these are materials that are made from two or more different materials to produce a material with new and useful properties)

  . The atoms are arranged in a hexagonal structure, just one atom thick

  . Graphene has some special properties

  . It is very strong, a good thermal and electrical conductor and nearly transparent
• Fullerenes


  Carbon molecules with hollow shapes, including tubes, balls and cages
• Fullerene molecules

  • Contain different numbers of carbon atoms
  • Have hollow shapes, including tubes, balls and cages
• Buckminsterfullerene

  The first fullerene to be discovered, consisting of 60 carbon atoms in a spherical shape
• Buckminsterfullerene

  • The atoms are joined together in a series of hexagons and pentagons
  • It is the most symmetrical and, therefore most stable fullerene
• Carbon nanotubes

  Cylindrical fullerenes with some very useful properties, can be very long compared with their width
• Uses of fullerenes

  • To deliver drugs in the body
  • In lubricants
  • As catalysts
  • For reinforcing materials, e.g. the frames of tennis rackets, so that they are strong but still lightweight
• Polymers

  . Polymers consist of very large molecules

  . Plastics are synthetic (man made) polymers

  . The atoms within the polymer molecules are held together by strong covalent bonds

  . The intermolecular forces between the large polymer molecules are also quite strong

  . This means that polymers are solid at room temperature

  . Poly(ethane), commonly known as polythene, is produced when lots of ethane molecules are joined together in an addition polymerisation reaction

  . It is cheap and strong and is used to make plastic bottles and bags
• Metallic Bonding

  . Metallic bonding occurs in:

  - metallic elements, such as iron and copper

  - alloys, such as stainless steel

  . Metals have a giant structure in which electrons in the outer shell are delocalised (not bound to one atom)

  . This produces a regular arrangement (lattice) of positive ions held together by electrostatic attraction to the delocalised electrons

  . A metallic bond is the attraction between the positive ions and the delocalised negatively charged electrons
• Properties of metals

  • They make metals very useful
  • Metallic bonds are very strong
  • Most metals have high melting and boiling points
  • They are useful structural materials
  • Delocalised electrons can move around freely and transfer energy
  • Metals are good thermal and electrical conductors
  • Particles in pure metals have a regular arrangement
  • Layers can slide over each other quite easily
  • Metals can be bent and shaped
• Copper is traditionally used to make water pipes
• Reason 1 for using copper for water pipes

  It is an unreactive metal, so it does not react with water
• Reason 2 for using copper for water pipes

  It can be easily shaped
• Key Point

  A metallic bond is the attraction between positive ions and delocalised electrons
• Alloys

  . Most metal objects are made from alloys - mixtures that contain a metal and at least one other element

  . Pure metals are too soft for many uses

  . In alloys, the added element disturbs the regular arrangement of the metal atoms so the layers do not slide over each other so easily

  . This means alloys are usually stronger and harder than pure metals