Group 2

• Atomic radius


  Increases down the group
• Atomic radius


  • As one goes down the group, the atoms have more shells of electrons making the atom bigger
• 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
• Melting points of Group 2 metals

  The distance between the positive ions and delocalized electrons increases
• Melting points of Group 2 metals

  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

  2. Form hydroxides
• Hydroxides produced


  Make the water alkaline (if they are soluble in water)
• Reaction of Mg with warm water

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

  2. Slower reaction than with steam

  3. No flame
• Titanium cannot be extracted with carbon because titanium carbide (TiC) it is formed rather than titanium
• Titanium cannot be extracted by electrolysis because it has to be very pure
• Extracting titanium


  1. TiO2 (solid) is converted to TiCl4 (liquid) at 900C

  2. The TiCl4 is purified by fractional distillation in an argon atmosphere

  3. The Ti is extracted by Mg in an argon atmosphere at 500C
• TiO2 converted to TiCl4


  TiCl4 can be purified by fractional distillation, being molecular (liquid at room temperature) rather than ionic like TiO2 (solid at room temperature)
• Titanium extraction process


  • Expensive due to the cost of magnesium
  • Batch process which is slow and requires more labour and energy
  • Requires argon and moisture removal (TiCl4 susceptible to hydrolysis)
  • High temperatures required in both steps
• Calcium oxide can be used to remove SO2 from waste gases by flue gas desulfurisation
• Flue gas desulfurisation


  1. Gases pass through a scrubber containing basic calcium oxide

  2. Reacts with the acidic sulfur dioxide in a neutralisation reaction
• Calcium sulfite


  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 used as a reagent

  2. If sulfate ions are present, a white precipitate of BaSO4 forms
• BaSO4 is used in medicine as a 'Barium meal' given to patients who need x-rays of their intestines
• Barium metal reacts slowly with sulfuric acid due to the formation of insoluble BaSO4
• The same effect happens to a lesser extent with metals going up the group as the solubility of the sulfates increases
• The same effect does not happen with other acids like hydrochloric or nitric as they form soluble group 2 salts
• Hydrochloric acid is needed to react with carbonate impurities that are often found in salts
• 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
• Calcium hydroxide solution


  More alkaline (pH 11) than magnesium hydroxide due to higher solubility
• Barium hydroxide


  Easily dissolves in water, making the solution strongly alkaline
• Magnesium hydroxide


  Insoluble in water, appears as a white precipitate, slightly alkaline (pH 9)
• Magnesium hydroxide


  Used in medicine (milk of magnesia) to neutralise excess acid and treat constipation
• Precipitation reactions


  Involve mixing appropriate solutions of ions to form an insoluble salt (precipitate)
• Ionic equations for precipitation reactions


  Show only the ions that are reacting and leave out spectator ions
• There are common rules for solubility of salts, but these do not need to be memorised
• Filtration is used to separate insoluble salts from the solution
• Gravitational filtration


  • Use if small amounts of solid are formed