Group 2

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  • Created by: emma
  • Created on: 22-03-14 21:42
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  • Group 2
    • Atomic radius
      • Increases down the group
        • More sheilding
        • Electrons added to shells further from nucleus
    • 1st ionisation
      • Decreases down group
        • Outer electrons further from nucleus and more sheilding
          • Less electrostatic force of attraction between outer electron and nucleus
            • Easier to knock electron off
    • Melting and boiling points
      • Decrease down group
        • Atoms get bigger and the same number of electrons in outer shell are more spread out and further from nucleus
          • Less attraction between outer electrons and nucleus
            • Weaker metallic bonds
    • Reactions with water
      • Increases in re-activity down group
        • Less attraction between outer electron and nucleus so electrons more easily lost
      • Mg(s)+H2O(g)= MgO(s)+ H2(g)
        • White precipitate
      • Ca(s)+ 2H2O(l) = Ca(OH)2(s) + H2(g)
        • Cloudy solution
      • Sr(g)+2H2O= Sr(OH)2(aq)+ H2(g)
        • Colourless solution
      • Ba(g)+2H2O(l)= Ba(HO)2(aq)+H2(g)
        • Colorless solution
    • Solubilities
      • Hydroxieds
        • Solubility increases
          • Mg(OH)2 used to neutralise excess stomach acid
          • Ca(OH)2 netralise acidic soil
      • Sulphates
        • Solubility decreases
        • Barium sulphate is insoluble and used as a barium meal
          • Ba2+ ions could not get into blood stream as held in BaSO4  solid
    • Test
      • Acidify with HCl to remove impurities
        • Add barium chloride
          • If sulphate ions are present a white precipitate forms
          • If testing for baruim ions add Na2SO4 or MgSO4 or just add H2SO4 at beginning a white precipitate forms
        • Not H2SO4 as it contains sulphate ions

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