Group 3

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• The study material covers topic questions, revision notes, and past papers for the listed subjects, exam boards, and qualification levels
• Period 3 Oxides


  • Reactions with oxygen
  • Reactions with chlorine
  • Reaction of sodium with water
  • Reaction of magnesium with water
  • Oxidation number of Period 3 oxides
  • Reaction of Period 3 oxides with water
• Reaction of sodium with cold water

  • 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
  • Sodium melts into a ball and moves across the water surface until it disappears
  • Hydrogen gas is given off
  • The solution formed is strongly alkaline (pH 14) due to the sodium hydroxide which is formed
• Reaction of magnesium with cold water

  • Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)
  • The solution formed is weakly alkaline (pH 11) as the formed magnesium hydroxide is only slightly soluble
  • When magnesium is heated, it reacts vigorously with steam (water) to make magnesium oxide and hydrogen gas: Mg(s) + H2O(g) → MgO(s) + H2(g)
• Electronegativity of oxygen


  Oxygen is more electronegative than any of the Period 3 elements
• Oxidation states of Period 3 elements in their oxides

  The Period 3 elements have positive oxidation states in their oxides and the oxygen has a negative oxidation state of -2
• Formulae of the oxides of the Period 3 elements & their oxidation states

  • Oxide formula
  • Oxidation state of Period 3 element
• Since aluminium oxide does not react or dissolve in water, the oxide layer protects the aluminium metal from corrosion
• Period 3 oxides react with or are soluble in water
• Reaction of Period 3 oxides with water