period 3

• Sodium and magnesium


  Both react ionically to form positive ions
• Sodium


  Reacts to form 1+ ions
• Magnesium


  Forms 2+ ions
• Sodium is more reactive than magnesium


  It only has to lose one electron to form an ion, whereas magnesium has to lose two electrons
• Less energy is required to ionise sodium


  Making it more reactive
• Reaction with magnesium is slow


  Using steam instead of water increases the speed of reaction
• Reaction with steam


  1. Provides greater energy

  2. Results in a violent reaction

  3. Magnesium burns with a bright white flame

  4. Produces hydrogen and magnesium oxide
• Period 3 elements react with oxygen to form oxides with each element in their highest oxidation state
• The number of the group is often the same as the highest oxidation state
• Period 3 oxides


  • Na2O
  • MgO
  • Al2O3
  • SiO2
  • P4O10
  • SO2
• Oxide Structure and Bonding

  • Relative Melting Point (oC)
  • Reactivity
• Na2O


  Ionic, ≈ 1250, Vigorous
• MgO


  Ionic, ≈ 2750, Vigorous
• Al2O3


  Ionic (covalent character), ≈ 2000, Slow (faster if powdered)
• SiO2


  Macromolecular, ≈ 1500, Slow
• P4O10


  Simple covalent, ≈ 500, Vigorous
• SO2


  Simple covalent, ≈ -10, Burns steadily
• Ionic oxides


  Combine with water to form alkaline solutions with a pH around 10-14
• Covalent oxides of sulfur and phosphorus


  Combine with water to form acidic solutions with a pH around 0-2
• In solution, these acids dissociate into H+ ions and ions of conjugate base
• Acid-base reactions


  1. Basic, ionic oxides react with acids to produce a salt and water (neutralisation)

  2. Acidic, covalent oxides react with bases to produce a salt and water (neutralisation)
• Aluminium oxide


  • Bonding is partially ionic and covalent
  • Insoluble in water as the ions don't dissociate
  • Can act as both an acid and a base (amphoteric)
  • Reacts as both to form a salt and water in neutralisation reactions