giant covalent structures

allotropes of carbon
1. diamond
  1. structure
    1. three dimensional lattice (network) of tetrahedral carbon atoms
    2. All of the carbon atoms are bonded to four other carbon atoms in a tetrahedral arrangement
    3. All of the valence electrons are used for bonding
  2. properties
    1. no valence electrons free for conduction of electricity
    2. high melting and boiling points
    3. the hardest naturally occurring substance due to its covalently bonded structure
    4. insoluble in covalent solvents
2. Graphite
  1. structure
    1. giant two dimensional layers
    2. held together in place by van der waals attractions
    3. layers consist of hexagons of carbon atoms
      1. each carbon bonded to three others
    4. one free electron per carbon atom that can be delocalised
    5. trigonal planar geometry
    6. 120 degrees bond angle
  2. properties
    1. black slippery solid
      1. as layers can slip over each other
    2. high melting and boiling point
3. Graphene
  1. innovations
    1. newly discovered
    2. trying to develop graphene sheets
    3. transparent and flexible computers
  2. structure
    1. contains single layers of graphite
      1. arranged hexagonally
      2. planar sheet of carbon atoms
    2. one atom thick
    3. arranged in a honeycomb crystalline lattice.
    4. covalently bonded to three other carbons
    5. can form nanotube, fullerene
  3. properties
    1. good conducter of electricity
      1. because of free to move delocalised electrons
    2. nearly transparent
    3. 200 times stronger than steel
4. C60 fullerenes
  1. structure
    1. graphite layer can be folded and bent into balls and tubes if the numebr of carbons is large enough
      1. bucky balls and nano tubes
    2. effectively two hemispherical geodhesic domes stuck together to make a sphere.
    3. not neccesarily a network solid
    4. composed of individual molecules with strong covalent bonds but with weak London forces between the molecules
    5. like a small sheet of graphite curved into a ball
    6. not a giant structure
  2. discovery
    1. developed from the discovery by Kroto of spherical molecules
      1. 60 carbons
    2. named after Richard Buckminster Fuller
  3. properties
    1. soluble in some polar substances
    2. do not conduct electricity
      1. because of symetrical nature
silicon dioxide (quartz)
1. structure
  1. giant macromolecular
    1. similar to diamond
  2. all valence electrons used to link silicon atoms
  3. tetrahedral
  4. oxygen atoms interposed between each pair of silicon atoms
  5. silicon bonded covalently to four oxygen atoms
  6. oxygen bonded covalently to two silicon atoms.
  7. bent as oxygen has two pairs of non bonding electrons
2. properties
  1. hard solid
  2. very high melting and boiling point
    1. due to strong covalent bonds
  3. non conductor
    1. as all valence electrons are used in bonding
    2. molten silicon dioxide can conduct electricity as electrons are free to move
  4. soluble in water

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giant covalent structures

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	Created by Jack Mcilduff almost 6 years ago