Atomic Structure and Properties <ul><li>Today we will discuss: </li></ul><ul><li>The structure of metals, insulators and s...
Metals <ul><li>Metals - Because the free electrons in metals: </li></ul><ul><ul><li>conduct well - are mobile and carry cu...
Insulators - Ceramics <ul><li>Ceramics - Because the ionic bonds holding them together: </li></ul><ul><li>are insulators -...
Insulators - Polymers <ul><li>Polymers - Because the covalent bonds stringing  monomers in long chains: </li></ul><ul><ul>...
Semi-Conductors <ul><li>These have properties in-between: </li></ul><ul><ul><li>Metals and </li></ul></ul><ul><ul><li>Insu...
Semiconductors and Conductivity
But what happens… <ul><li>When things get hot!!!?!?!?!? </li></ul><ul><li>Using a beaker, tripod, multimeter, a piece of w...
What is happening…?
Doping <ul><li>Obviously it is not practical to heat up semiconductors – to increase conductivity we ‘dope’ them with othe...
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  1. 1. Atomic Structure and Properties <ul><li>Today we will discuss: </li></ul><ul><li>The structure of metals, insulators and semi-conductors and how this affects: </li></ul><ul><ul><ul><li>Electrical properties </li></ul></ul></ul><ul><ul><ul><li>Appearance </li></ul></ul></ul><ul><ul><ul><li>Mechanical properties </li></ul></ul></ul>29 May 2009
  2. 2. Metals <ul><li>Metals - Because the free electrons in metals: </li></ul><ul><ul><li>conduct well - are mobile and carry current </li></ul></ul><ul><ul><li>are shiny - oscillate in light, scattering light photons </li></ul></ul><ul><ul><li>are stiff - ‘glue’ ions together strongly </li></ul></ul><ul><ul><li>are ductile - provide non-directional glue, letting ions slip </li></ul></ul>All atoms are ionised and the electrons are free to move…
  3. 3. Insulators - Ceramics <ul><li>Ceramics - Because the ionic bonds holding them together: </li></ul><ul><li>are insulators - lock electrons to ions or atoms, so none are free to move </li></ul><ul><li>are stiff - are hard to stretch strong bonds </li></ul><ul><li>are brittle - are directional bonds, so that atoms or ions cannot slip </li></ul>Electrons lock to ions so none are free to move…
  4. 4. Insulators - Polymers <ul><li>Polymers - Because the covalent bonds stringing monomers in long chains: </li></ul><ul><ul><li>are insulators - lock electrons to atoms, with none free to move </li></ul></ul><ul><ul><li>are often flexible- can rotate, letting chains stretch or fold </li></ul></ul><ul><ul><li>are often plastic – make chains which can slip past one another </li></ul></ul>The covalent bonds, stringing monomers into long chains…
  5. 5. Semi-Conductors <ul><li>These have properties in-between: </li></ul><ul><ul><li>Metals and </li></ul></ul><ul><ul><li>Insulators </li></ul></ul><ul><ul><li>These have far fewer ionised atoms (and hence fee electrons) </li></ul></ul>
  6. 6. Semiconductors and Conductivity
  7. 7. But what happens… <ul><li>When things get hot!!!?!?!?!? </li></ul><ul><li>Using a beaker, tripod, multimeter, a piece of wire and a semiconductor sample (thermistor), test: </li></ul><ul><li>The effect of temperature on conductivity (measure resistance) of metals and semiconductors… </li></ul>
  8. 8. What is happening…?
  9. 9. Doping <ul><li>Obviously it is not practical to heat up semiconductors – to increase conductivity we ‘dope’ them with other atoms. </li></ul><ul><li>Using page 124 summarise, with pictures, the 2 types of doping </li></ul>

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