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Topic 2 Bonding, structure, and the properties of matter By Bethan Poole…

- - - - Covalent
        
        Share electrons
        
        Occurs in most non-mettalic elements and in compounds of non-metals
      - Metallic
        
        Share delocalised electrons
        
        Occurs in metallic elements and alloys
      - Ionic
        
        They are oppositely charged ions
        
        Occurs in compounds formed from metals combined with non-metals
  - - - Sodium Chloride
        
        Each sodium atom transfers an electron to each chlorine atom so they all have 8 electrons in their outer shells
        
        Form ions of Na+ and Cl- and compound formed is NaCl
        
        2Na+Cl2->2NaCl
  - - - Chlorine has 7 electrons in its outer shell in order to bond with another chlorine atom:
        
        An electron from each atom is shared
        
        Gives chlorine 8 in its outer shell- complete out shell
    - - Non-metallic elements
      - Compounds of non-metals
  - - - Metallic elements- iron and copper etc.
      - Alloys- stainless steel
- - - - Random arrangement
      - Close together
      - Flow around each other
    - - :
      - Random arrangement
      - Much further apart
      - Move very quickly in all directions
    - - Regular arrangement
      - Very close together
      - Vibrate around fixed positions
    - - The amount of energy needed to change state depends on the amount of energy needed to overcome the forces of attraction between the particles
      - Stronger the forces of attraction the:
        
        Greater the amount of energy needed to overcome them
        
        Higher the melting point and boiling points will be
  - - - Plastics are synthetic polymers
      - Atoms within polymers are held together by strong covalent bonds
      - Intermolecular forces between the large molecules are quite strong
      - Solid at room temperature
      - Poly(ethene)- lots of ethene molecules are joined together in an addition polymerisation reaction- cheap and strong - used to back plastic bags and bottles
      - Consist of very large molecues
  - - - Strong metallic bonds
      - High melting and boiling point
      - Delocalised electrons move freely and transfer energy- Good thermal and electrical structures
      - Pure metals have a regular arrangement
      - Layers can slide so they can be bent and shaped
    - - Mixtures that contain a metal and one other metal
      - The added element disturbs the regular arrangement so layers don't slide so easily
      - Alloys are stronger and harded than pure metals
- - - - So layers can slide past each other making graphite soft and slippery
    - - They allow grapite to conduct electricity and heat
  - - - Form of carbon
      - It's a single layer of graphite
      - Atoms arranged in a hexagonal structure- one atom thick
      - Very strong
      - Good thermal and electrical structure conductors
      - Nearly transparent
    - - Carbon can form fullerenes- containing different numbers of carbon atoms
      - Structure based on hexagonal rings of carbon atoms- sometimes the rings contain 5 or 7 carbon atoms
      - First fullerene discovered was buckminsterfullerene, C60
        
        Consists of 60 carbon atoms
        
        Atoms joined together in a series of hexagons and pentagons
        
        It's the most symmetrical and stable fullerene
      - Properties of carbon nanotubes make them useful for use in nanotechnology, electronics and materials
      - Can be used to deliver drugs into the body; in lubricants; as catalysts; for reinforcing materials; e.g in the frames of tennis rackets so they're strong but lightweight
- - - - diameter between 1nm and 100nm or 1x10-9 and 1x10-7
    - - The study of these very small structures
  - - - Provide better skin coverage
      - So are more effective to protect against the suns rays
      - Concerns- so small they could get into someone's skin and damage human cells or cause damage to the enviroment
    - - Computers and technology
      - Synthetic skin for burn victims
      - Catalysts for fuel cells
      - Stronger and lighter construction materials
      - New cosmetics and deodrants
      - Fabrics that prevent the growth of bacteria
      - New drug delivery systems