C3: PART ONE

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  • C3: PART ONE
    • THE EARLY PERIODIC TABLE
      • By the early 1800's less that 40 elements discoverd
        • New one's discovered regularly
        • Patterns in reaction
        • New properties discovered (eg atomic weight)
      • NEWLAND'S PERIODIC TABLE
        • in order of atomic mass. organised in octaves. only worked for first few elements: metals and non-metals together.
      • MENDELEV'S PERIODIC TABLE
        • Organised in periodic way (regularly occurring pattern). Gaps for new elements. More to be discovered.
    • THE MODERN PERIODIC TABLE
      • Many things changed since Mendelev.
        • Ordered by atomic number. Groups by outer shell. Group 0/8 has full outer shell.
    • GROUP 1: ALKALI METALS
      • Low density. React with non-metals to morn ionic compound. react with water to release hydrogen.
      • The further down you go: the MORE reactive the element and the LOWER the boiling and melting points.
    • TRANSITION ELEMENTS
      • Between groups 2 and 3, the largest of the groups (contains most elements).
      • Compared to group 1: higher melting/boiling points, harder/stronger, less reactive
      • Form ions with different charges (Fe2+ and Fe3+). Coloured compounds. Useful as catalysts (e.g iron and nickel).
    • GROUP 7: THE HALOGENS
      • Poor conductors of heat and electricity. Poisonous. Produce colourful vapours.
      • React with metals to form ionic compound. Ion is called a halide and has a charge of -1.
      • Further down the group: the LESS reactive the element but the HIGHER the boiling/melting point.
      • a MORE reactive halogen can DISPLACE a LESS reactive halogen from an aqueous solution of it's salt.
    • TRENDS IN REACTIVITY
      • as you go down group 1,elements are MORE reactive. as you go down group 7, elements are LESS reactive.
      • the higher the ENERGY LEVEL OF OUTER SHELL ELECTRONS: the more easily electrons are lost, less easily electrons are gained.
      • GROUP 1: When outer electrons are closer to nucleus: stronger attraction, less screening (inner electrons) electrons lost LESS easily.
    • SOFT AND HARD WATER
      • Mix water with soap:  if it lathers it's soft water.
        • Temporary can be softened by heating/boiling, permanent hard water can't
      • Hard water contains magnesium and calcium compounds
      • Scum and scale reduce efficiency. Good bone and teeth development. Reduce heart disease.
    • SOFTENING HARD WATER
      • Add 'washing soda' (sodium carbonate). Ca + CO -> CaCO3 +Na
      • Ion exchange column with resin. Na or H is exchanged with Ca or Mg.
      • HIGHER: temporary water contains hydrogen carbonate ions. When heated, these decompose to carbonate ions. These react to Mg or Ca ions.

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