C9 group 2 elements

• atomic radius increases down group 2 due to increasing number of electron shells
• reactivity increases down group 2 as electrons get increasingly far from the nucleus so nuclear attraction is weaker
• first and second ionisation energy decrease down group 2 as atomic radius increases and shielding increases
• melting points decrease down group 2 due to ion size increasing, which weakens the electrostatic attractions in the metallic lattice as delocalised electrons are further from the nuclei
• group 2 metals react with water in a redox reaction which produces a metal hydroxide and hydrogen, this creates an alkaline solution
• the solubility of group 2 hydroxides increases going down the group
• Mg(OH)2 is sparingly soluble

  Ba(OH)2 is the most soluble
• Mg(OH)2 is used in medicine as an antacid because it is alkaline so neutralises stomach acid
• Ca(OH)2 is used in agriculture to neutralise acidic soil because it is alkaline
• group 2 metals react with sulfate ions to produce metal sulfates
• the solubility of group 2 sulfates decreases going down the group
• MgSO4 is the most soluble

  BaSO4 is the least soluble
• BaSO4 is used in medicine as barium meals to outline soft tissue in X-rays, it is toxic if it enters the bloodstream but because it is insoluble it cannot do so
• BaCl2 is used as a test for sulfate ions because it reacts to form barium sulfate, a white precipitate
• test for sulfates:

  • acidify with nitric or hydrochloric acid
  • add barium chloride
  • positive = white precipitate
• when testing for sulfates, you need to first acidify the sample using nitric or hydrochloric acid to remove any carbonate ions which would produce barium carbonate, a white precipitate, so a false positive
• magnesium is used in the extraction of titanium from titanium chloride by a displacement reaction
• the equation for magnesium being used in the extraction of titanium is:

  TiCl4 + 2Mg -> 2MgCl2 + Ti
• calcium oxide is used in flue gas desulfurisation, to remove SO2 from the gases released into the environment, as SO2 causes acid rain and photochemical smog
• the equation for calcium oxide being used in flue gas desulfurisation is:

  CaO + 2H2O + SO2 -> CaSO3 + 2H2O