Chemistry 2 Revision

Notes for success in chemistry 2

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Modern Periodic Table

  • Use relative atomic mass to determine the mass of an electron
  • Carbon contains 6 protons and 6 neutrons so its relative atomic mass is 12
  • Helium is a noble atom: 2 neutrons and 2 protons so its RAM is 4

The Modern Periodic Table

  • Order is based on inceasing atomic number, as Mendeleev did
  • Horizontal Rows are called periods, veritcal columns are known as groups
  • Each group contains elements with the same properties
  • Main groups are 1 - 7, based on electron configuration


  • Different atoms of the same element
  • Proton number defines atom; chlorine contains 17 protons, yet some have 18/20 neutrons
  • The relative abundance of chlorine of 35/17 Cl is 75% chlorine atom, while the proportion of 37/17 is 25%. This is why the relative atomic mass of chlorine is 35.5 rather than a whole number

Relative atomic mass = (75x35)+(25x37) / (75+25) = 2625+925 / 100 = 3550/100 = 35.5

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Ion tests

Ion Flame Tests - Cations

  • Calium Ca2+ - Brick Red
  • Copper Cu2+ - Green/Blue
  • Sodium Na+ - Yellow
  • Potassium K+ - Lilac

Precipitation Tests

  • To identify aqueaus chloride anaions - a few drops of nitric aicd and silver nitrate, a white precipitate is formed
  • Sulphate anions - dilute hydrochloric acid and barium chloride = white precipitate of barium sulphate

Test for carbonate ions

  • Any acid, CO2 produced, bubbled through limewater, goes milky
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Inks, paints and food contain mixtures of coloured compounds. Chromatography can be used to detect what colouring is in those substance

Process -

  • Substance are put on a start line on a piece of paper; which is drawn in pencil as it doesn't contain ink
  • The substances have different solubility so some move at different speeds and distances
  • A substance can identified by comparing the horizontal spots 

Chromatography can identify substances by using

Rf values = distance moved by soluable subtance


                           distance moved by solvent

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Properties of Covalent Structures

Diamond -

  • very hard because all atoms are joined with strong covalent bonds
  • used to make cutting tools
  • do not conduct electricty because there are no 
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