C2 1

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  • Created by: Florence
  • Created on: 18-11-12 11:37

C2 1.1

  •   Element – a substance made from only one type of atom.
    •  It cannot be broken down into simple substances.
    •  All elements are listed in the periodic table.
  • Compound - a substance made from different elemnets chemically joined together.
    • The properties of a compound are different to those of the elements from which it was made.
    • Compounds can be docomposed (broken down) int simpler substances. This can be achieved by:
      • heating (thermal decomposition).
      • Electricity (electrolysis) - passing a current through the substance.
  • Properties of each substance in a mixture are the same as before they were mixed.

C2 1.2

  • Noble gases
    • Found in group 0 of the periodic table.
    • Do not join in any reactions at all - very unreactive
    • They are very stable because they have full outer electron shells (energy levels).
  • Atoms are made of:
    • A central nucleus - containing protons and neutrons.
    • Electrons circling the nucleus in different energy levels
      • Energy levels acn only take a certain number of electrons:
        • First energy level - up to 2 electrons
        • Second energy level - up to 8 electrons
        • Third energy level - up to 8 electrons
  • Other less stable elements take part in chemical reactions to gain a full outer energy level. To do this they will:
    • Give away electrons to other elements to lose an energy level and move down to a full one.
    • Take electrons from other elements to fill their outer energy level.
  • Electrons, protons and neutrons all ahve different charges:
    • Protons have a positive charge +
    • Electrons have a negative charge -
    • Neutrons have no charge 0
  • If an atom:
    • Loses an electron it now has one more proton than electrons and a single positive charge. It is called an ion
    • Gains an electron it now has one more electron than protons and a single negative charge. It is now an ion.
      • Negative ions are called halide ions.
  • All…

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