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Module 2 - atoms and reactions, formulae and moles - 2.1.5-11, atoms, ions…

- - - - some atoms form more than one ion each with a different charge
- - - - divide the amount of each element by its molar mass
      - divide the answer for each element by the smallest number to get the ratio in the format 1 : x
      - if necessary, multiply the answer by a suitable value to make sure the ratio is in whole numbers
  - - - work out the empirical formula mass
      - divide the Mr by the empirical formula mass to get the number of units in a molecule
      - multiply the unit by the number of units in a molecule
- - - - a large amount of solute per dm^3
    - - a small amount of solute per dm^3
- - - - the volume per mole of a gas, dm^3 mol^-1, at RTP the molar volume is approx. 24.0 dm^3 mol^-1
- - - - Dalton's atomic theory
        
        atoms are tiny particles that make up elements; atoms cannot be divided; atoms of one element are different from those of every other element
        
        J.J. Thomson plum pudding
        
        negative electrons moving around in a 'sea' of positive charge; the overall negative charge is equal to the overall positive charge
        
        Ernest Rutherford's gold leaf experiment
        
        fired alpha particles at gold foil; the plum pudding model would hardly deflect the particles; most particles were not deflected, some were deflected at large angles, very few deflected back towards the source
        
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        new atomic model; the positive charge and most of its mass are concentrrated in the centre of the atom, negative electrons orbit this nucleus, most of an atom's volume would be the space between the nucleus and electrons,the overall charges must balance
        
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- - - - isotopes of an element react in the same way; chemical reactions do not involve neutrons
- - - - % abundance of isotope = (height of isotope/total height of all peaks) x 100
    - - Ar = Σ(isotopic mass x abundance)/Σ abundance