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  • Created by: SJC
  • Created on: 16-05-13 18:47
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  • Electron shells
    • Electron shell rules:
      • 1) Electrons always occupy shells ( sometimes called energy levels).
      • 2) The lowest energy levels are always filled first- these are the ones closest to the nucleus
      • 3) Only a certain number of electrons are allowed in each shell:
        • 1st shell: 2,  2nd shell: 8, 3rd shell: 8
      • 4) Atoms are much happier when they have a full electron shells- like the noble gases in group 0.
      • 5) In most atoms the outer shell is not and this makes the atom want to react
    • Follow the rules to work out electron configurations
      • 1) The periodic table tells us nitrogen has seven protons..... so it must have seven electrons
      • 2) Follow the 'Electon shell rules'. The first shell can only take 2 electrons and the second shell can take a maximum of 8 electrons
      • 3) so the electron configuration for nitrogen must be 2,5.


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