Structure and Properties 2

Giant ionic structures 2.1
1. ionic compounds have giant structures
  1. strong electrostatic forces hold the ions together
2. solid at room temperature
  1. can't conduct electricity
    1. no free electrons
    2. ions can only vibrate about fixed positions
3. high melting and boiling points
  1. large amount of energy need to overcome ionic bonds
4. when melted the ions are free to move
  1. can carry electrical charge
5. some compounds can dissolve in water
  1. water molecules split up the lattice
    1. ions are free to move so can conduct electricity
Simple Molecules 2.2
1. atoms within a molecule are held together by strong covalent bonds
  1. bonds only act between the atoms within the molecule
    1. molecules have little attraction for each other
2. low melting and boiling points
  1. intermolecular forces are weak and easily overcome
3. cannot conduct electricity as the molecule has no overall charge
Giant Covalent Structures 2.3
1. atoms can sometimes form several covalent bonds
  1. these join together to form giant covalent structures or macromolecules
  2. every atom is joined to several other atoms by strong covalent bonds
    1. has a high melting point as teh bonds are difficult to break/overcome
2. Diamond
  1. made of carbon
  2. regular 3D giant structure
    1. the atoms lock into place
  3. covalently bonded to 4 other carbon atoms
    1. makes it hard
    2. makes it transparent
3. Graphite
  1. covalently bonded to 3 other carbon atoms
    1. 1 electron from each carbon is delocalised
      1. this allows graphite to conduct heat and electricity
  2. formed in flat hexagonal 2D layers
    1. no covalent bonds between layers
      1. there are weak intermolecular forces
        makes graphite soft and maluable as layers slide over each other
  3. Fullerenenes
    1. take the hexagonal layers and join them to form cage like structures
      1. nano sizes so can be used to deliver drugs around the body and to reinforce materials
Giant Metallic structures 2.4
1. metal atoms are arranged in layers
  1. when force is applied they slide over each other
    1. metal bends/stretches
      1. useful for making wires and rods
2. alloys are mixtures of metals/non-metals
  1. due to the different sized atoms they distort the layers
    1. make the layers difficult to slide over each other
      1. harder than pure metals
3. Shape memory alloys
  1. bent or deformed
    1. when heated they return to their original shape
      1. dental braces
4. metals have delocalised electrons
  1. good conductors of heat and electricity
    1. electrons can move quickly through the lattice
Properties of polymers 2.5
1. depend of the monomer used to make it and the conditions
2. thermosoftening polymer
  1. poly(ethene)
    1. polymer chains are tangled together
      1. this means it can be reheated and re-moulded before setting hard again
      2. weak forces hold them together and are broken when heated
        when it cools the forces bring the molecules back together
3. thermosetting polymer
  1. set hard when first moulded
    1. strong covalent bonds cross link between the chains
Nano Science 2.6
1. atoms are arranged into very small particals
  1. which behave differently to ordinary materials made of the same atom
2. a nanometre is 1 billionth of a metre
  1. nanoparticals are a few nanometres in size
    1. because of this they have a large surface area making them very useful
3. how it is used:
  1. catalysts
  2. cosmetics
  3. sun screens
  4. deodorants
4. the more they are used the greater risk of them getting into the air and our bodies
  1. unpredictable consequences
    1. more research needs to be done

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	Created by vicky.pratt almost 11 years ago