Group 2

• Melting points


  High because they have giant metallic structure with strong attraction between + metal ions and delocalised e-, requires lots of energy to break
• Density


  harder and have higher density than group 1 elements because group 2 ions are smaller than group 1 ions so they can pack more closely
• Reactivity

  Group 2 elements are all reactive metals with similar chemical reactions because they all have 2 outer e-
• Appearance of group 2 compounds

  ionic, white crystalline solids
• Atomic radius


  increases down group2

  more shells of e-, more shielding, less nuclear attraction to outer e-
• Magnesium reaction with cold water

  very slow reaction

  Mg (s) + 2H2O -> Mg(OH)2 (s) + H2 (g)
• Mg with steam


  Much faster

  white light and white solid

  Mg (S) + 2H2O (g) -> MgO (s) + H2 (g)
• Calcium and cold water

  fizzing. white solid, dissolves to form an alkali solution

  Ca (s) + 2H2O (L) -> Ca(OH)2 + H2
• Reactivity of group 2 with water

  Increases down the group
• Solubility of group 2 hydroxides down the group

  increases
• Why is titanium useful?

  Strength, many applications in aerospace, marine and motor vehicle industries
• Difficult to extract titanium from its ores TiO2 because reduction with carbon produces a brittle titanium carbide TiC
• 1. Reacted with chlorine first and carbon


  TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
• Then reduced with magnesium

  TiCl4 + 2Mg -> Ti + 2 MgCl2
• Group 2 hydroxides are bases and react with acids


  M(OH)2 + 2HCL -> MCL2 + 2H2O

  M(OH)2 + H2SO4 -> MSO4 + 2H2O
• pH of magnesium hydroxide and barium hydroxide

  Mg(OH)2 - 8

  Ba(OH)2-13
• So pH of the resulting solution increases down group 2
• Uses of magnesium hydroxide

  indigestion remedies- Milk of Magnesia can neutralise stomach acid
• Uses of calcium hydroxide


  used to neutralise acidic soil
• Group 2 sulfates


  solubility decreases, Calcium sulfate is sparingly soluble, Barium sulfate is insoluble
• How to confirm presence of Mg2+ ions


  Add NaOH and observe ppt formed

  MgCl2 + 2NaOH -> Mg(OH)2 + 2NaCl

  Magnesium hydroxide is sparingly soluble, so a thick white ppt would be seen

  Mg2+ (aq) + 2OH- (aq) -> Mg(OH)2 (s)

  barium hydroxide does not form a ppt, so a colourless solution would be seen
• How to confirm presence of Ba2+ ions

  add sulfuric acid

  MgSO4 soluble so colourless solution

  BaSO4 insoluble, so thick white ppt would be seen

  Ba2+ (aq) + SO4 2- (aq) -> BaSO4 (s)
• Uses of barium salts

  used to test for sulfate ions

  Method: Add 1 cm3 of unknown solution

  add 1 cm3 of HCL to remove interfering ions

  Add 1 cm3 BaCl2, if SO4 2- are present, a thick white ppt is seen
• Barium meal


  BaSO4 can absorb X rays, even though barium ions are toxic, because baso4 is insoluble it's not absorbed into the blood
• Magnesium salts use


  test for hydroxide ions

  Add 1cm3 of unknown

  add 1 cm3 of MgCl2, if OH- are present, white ppt is seen

  Mg2+ (aq) + 2OH- (aq) -> Mg(OH)2 (s)
• Uses of calcium compounds

  CaO or CaCO3 can be used to remove sulfur dioxide from flue gas

  they are both basic so they can neutralise SO2 an acidic gas

  CaO + SO2 -> CaSO3

  CaCO3 + SO2 -> CaSO3 + CO2