Group 2

• Atomic radius


  Increases down the group
• Atomic radius


  • Atoms have more shells of electrons making the atom bigger as you go down the group
• 1st Ionisation Energy


  The outermost electrons are held more weakly because they are successively further from the nucleus in additional shells
• 1st Ionisation Energy


  The outer shell electrons become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons
• Melting points of Group 2 metals

  Decrease down the group
• Melting points of Group 2 metals


  The metallic bonding weakens as the atomic size increases. The distance between the positive ions and delocalized electrons increases. Therefore the electrostatic attractive forces between the positive ions and the delocalized electrons weaken
• Reactivity of Group 2 metals

  Increases down the group
• Reaction of Mg with oxygen

  1. Mg burns with a bright white flame

  2. MgO appears as a white powder
• Reaction of Mg with steam

  1. Mg reacts to produce magnesium oxide and hydrogen

  2. Mg would burn with a bright white flame

  3. MgO appears as a white powder
• Reaction of Group 2 metals with cold water

  1. Increasing vigour down the group to form hydroxides

  2. Fizzing (more vigorous down group)

  3. Metal dissolving (faster down group)

  4. Solution heating up (more down group)

  5. White precipitate forming (less precipitate forms down group)
• Reaction of Mg with warm water

  1. Mg + 2 H2O Mg(OH)2 + H2

  2. Slower reaction than with steam

  3. No flame
• Titanium


  • Abundant
  • Low density
  • Corrosion resistant
  • Used for making strong, light alloys for use in aircraft
• Extracting titanium


  1. TiO2 converted to TiCl4 at 900C

  2. TiCl4 purified by fractional distillation in argon atmosphere

  3. Ti extracted by Mg in argon atmosphere at 500C
• Reason titanium is expensive

  • Expensive cost of the magnesium
  • Batch process is slow and requires more labour and energy
  • Need for argon and to remove moisture
  • High temperatures required
• Calcium oxide can be used to remove SO2 from waste gases by flue gas desulfurisation
• Removing SO2 from waste gases

  1. Gases pass through a scrubber containing basic calcium oxide

  2. Calcium oxide reacts with acidic sulfur dioxide in a neutralisation reaction

  3. Calcium sulfite formed can be used to make calcium sulfate for plasterboard
• Group II sulfates


  Become less soluble down the group, with BaSO4 being the least soluble
• Testing for presence of sulfate ion

  1. Acidified BaCl2 solution is added

  2. White precipitate of BaSO4 forms if sulfate ions present
• Barium sulfate is used in medicine as a 'Barium meal' given to patients who need x-rays of their intestines
• Barium sulfate is safe to use because its low solubility means it is not absorbed into the blood
• If barium metal is reacted with sulfuric acid

  It will only react slowly, as the insoluble barium sulfate produced will cover the surface of the metal and act as a barrier to further attack
• Group II hydroxides


  Become more soluble down the group
• Calcium hydroxide


  • Partially soluble in water
  • Appears as a white precipitate
  • Used in agriculture to neutralise acidic soils
  • Aqueous solution (limewater) can be used to test for carbon dioxide
• Barium hydroxide


  • Easily dissolves in water
  • Makes the solution strongly alkaline
• Magnesium hydroxide


  • Insoluble in water
  • Slightly alkaline suspension in water (pH 9)
  • Used in medicine to neutralise excess acid in the stomach and treat constipation
• Making insoluble salts by precipitation

  1. Mix appropriate solutions of ions so that a precipitate is formed

  2. Precipitate is removed by filtration, washed and dried
• Ionic equations for precipitation reactions


  Show only the ions that are reacting and leave out spectator ions
• Common rules for solubility of salts
• Filtration


  • Gravitational filtration used for small amounts of solid
  • Vacuum filtration used for larger amounts of solid