Group 2

• Melting points of Group 2 elements

  • Decrease down the group
  • Metallic bonding weakens as atomic size increases
  • Distance between positive ions and delocalized electrons increases
  • Electrostatic attractive forces between positive ions and delocalized electrons weaken
• Atomic radius of Group 2 elements

  • Increases down the group
  • Atoms have more shells of electrons making the atom bigger
• 1st Ionisation Energy of Group 2 elements

  • Outermost electrons are held more weakly because they are successively further from the nucleus in additional shells
  • Outer shell electrons become more shielded from the attraction of the nucleus by the repulsive force of inner shell electrons
• Reactions of Group 2 metals with oxygen

  1. Group 2 metals will burn in oxygen

  2. Mg burns with a bright white flame

  3. 2Mg + O2 → 2MgO

  4. MgO is a white solid with a high melting point due to its ionic bonding

  5. Reactivity of group 2 metals increases down the group

  6. Mg will also react slowly with oxygen without a flame

  7. Mg ribbon will often have a thin layer of magnesium oxide on it formed by reaction with oxygen
• Reactions of Mg with acids

  1. Mg + 2HCl → MgCl2 + H2

  2. MgO + 2HCl → MgCl2 + H2O
• Reactions of Mg with water

  1. Mg + 2H2O → Mg(OH)2 + H2

  2. Mg(s) + H2O(g) → MgO(s) + H2(g)

  3. Other group 2 metals react with cold water with increasing vigour down the group to form hydroxides
• Extraction of titanium


  • Titanium is extracted by reaction with a more reactive metal (e.g. Mg)
  • TiO2 is converted to TiCl4 which is then purified by fractional distillation
  • The Ti is extracted by Mg in an argon atmosphere at 500°C
• Titanium cannot be extracted with carbon because titanium carbide (TiC) is formed rather than titanium
• Titanium cannot be extracted by electrolysis because it has to be very pure
• TiO2 is converted to TiCl4 as it can be purified by fractional distillation, TiCl4 being molecular (liquid at room temperature) rather than ionic like TiO2 (solid at room temperature)
• Solubility of Group 2 hydroxides

  • Become more soluble down the group
  • All appear as white precipitates when not soluble
• Magnesium hydroxide


  • Classed as insoluble in water
  • Simplest Ionic Equation: Mg2+ (aq) + 2OH-(aq) = Mg(OH)2 (s)
  • Suspension in water appears slightly alkaline (pH 9)
  • Used in medicine to neutralise excess acid in the stomach and to treat constipation
• Calcium hydroxide


  • Classed as partially soluble in water
  • Appears as a white precipitate
  • Used in agriculture to neutralise acidic soils
  • Suspension in water appears more alkaline (pH 11) than magnesium hydroxide
  • Aqueous solution called lime water can be used as a test for carbon dioxide
• Solubility of Group 2 sulfates

  • Become less soluble down the group
  • BaSO4 is the least soluble
• Formation of insoluble sulfate precipitates

  1. Full equation: SrCl2(aq) + Na2SO4 (aq) = 2NaCl (aq) + SrSO4 (s)

  2. Simplest ionic equation: Sr2+ (aq) + SO42-(aq) = SrSO4 (s)
• Barium sulfate


  • Used in medicine as a 'Barium meal' given to patients who need x-rays of their intestines
  • Its low solubility means it is not absorbed into the blood
• Reaction of barium metal with sulfuric acid


  Barium sulfate produced will cover the surface of the metal and act as a barrier to further attack
• Testing for the presence of sulfate ions

  1. BaCl2 solution acidified with hydrochloric acid is used as a reagent

  2. If acidified barium chloride is added to a solution containing sulfate ions, a white precipitate of barium sulfate forms

  3. The hydrochloric acid is needed to react with carbonate impurities that would form a white barium carbonate precipitate and give a false result
• Simplest ionic equation for barium sulfate precipitation

  Ba2+ (aq) + SO42-(aq) = BaSO4 (s)
• Precipitation reactions


  • Insoluble salts can be made by mixing appropriate solutions of ions so that a precipitate is formed
  • Precipitate is a solid
  • Soluble salts, insoluble salts, and common rules for solubility of salts
• Filtration of precipitates


  1. Gravitational filtration for small amounts of solid

  2. Vacuum filtration for larger amounts of solid

  3. Filter paper is drawn on the diagram for both types of filtration apparatus
• Writing ionic equations for precipitation reactions

  Take full equation, separate into (aq) solutions, cancel out spectator ions to leave simplest ionic equation
• Spectator ions


  Ions that are not changing state or oxidation number