C3: PART ONE
- Created by: Georgia Barnaby
- Created on: 05-05-14 19:08
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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.
- By the early 1800's less that 40 elements discoverd
- THE MODERN PERIODIC TABLE
- Many things changed since Mendelev.
- Ordered by atomic number. Groups by outer shell. Group 0/8 has full outer shell.
- Many things changed since Mendelev.
- 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.
- Mix water with soap: if it lathers it's soft water.
- 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.
- THE EARLY PERIODIC TABLE
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