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Chemical Changes (Reactivity of metals (Oxidation and reduction (To be…

- - - - the more easily it loses electrons in reactions to form positive ions (cations)
      - the more vigorous its reactions are
    - - Potassium
        Sodium
        Lithium
        Calcium
        Magnesium
        Carbon
        Zinc Iron
        Hydrogen
        Copper
        Gold
  - - - Known as oxidation reactions because the metals gain oxygen
  - - - In this reaction, carbon is oxidized because it gains oxygen. At the same time, copper oxide is reduced because oxygen is removed from it.
      - Oxidation is the gain of oxygen. Reduction is the loss of oxygen.
  - - - They are redox reactions
      - A more reactive metal can displace a less reactive metal from its compounds.
        
        For example, magnesium is more reactive than copper. It displaces copper from copper sulfate solution:
        
        Magnesium + copper sulfate → magnesium sulfate + copper
        Mg(s) + CuSO_4(aq) → MgSO-4(aq) + Cu(s)
        
        In this displacement reaction:
        
        magnesium becomes coated with copper
        
        the blue colour of the solution fades as the blue copper sulfate solution is replaced by colourless magnesium sulfate solution
      - A balanced equation can be written in terms of the ions involved:
        
        Mg(s) + Cu ^2+(aq) + SO_4^2-(aq) → Mg^2+(aq) + SO_4^2-(aq) + Cu(s)
        
        Sulfate ions, SO_4^2-, appear on both sides of the equation, but they do not take part in the reaction (they are called spectator ions). The equation can be rewritten without them:
        
        Mg(s) + Cu^2+(aq) → Mg^2+(aq) + Cu(s)
        
        This equation is an example of a balanced ionic equation. It can be split into two half equations :
        
        In an ionic equation only the particles that react and the products they form are shown.
        
        Mg(s) → Mg^2+(aq) + 2e- (oxidation)
        
        Cu^2+(aq) + 2e- → Cu(s) (reduction)
        
        Magnesium atoms lose electrons- they are oxidised
        
        Copper ions gain electrons- they are reduced
        
        Reduction and oxidation happen at the same time, so the reactions are called redox reactions.
    - - if sodium is oxidised, it has lost an electron, leaving it with a +1 charge, so the ionic equation is: Na → (Na ^+) + (e ^-)
      - if sodium +1 ion is reduced, it has gained an electron, leaving it with a charge of zero, so the ionic equation is: (Na ^+) + (e ^-) → Na
      - remember: the charges on each side of the equation should add up to the same number.
    - - e.g. 2Na + 2HCl -> 2NaCl + H_2
      - HCl is made up of (H ^+) and (Cl ^-) ions & NaCl is made up of (Na ^+) and (Cl ^-) ions
      - looking at just sodium: 2Na → (2Na ^+) , so the ionic equation must be: 2Na -> (2Na ^+) + (2e ^-) , meaning sodium has lost electrons & has been oxidised.
      - looking at just chlorine: (2Cl ^-) → (2Cl ^-), meaning chlorine has not been oxidised or reduced.
      - looking at just hydrogen: (2H ^+) →H_2 , so the ionic equation must be: (2H ^+) + (2e ^-) →H_2 , meaning hydrogen has gained electrons so has been reduced.