group 2 (alkaline earth metals)

• trend in atomic radius (group 2)

  atomic radius increases

  • extra shells (shielding)
• trend in ionisation energy (group 2)

  ionisation energy decreases

  • more shielding
  • weaker attraction to nucleus - easier to remove electrons
• trend in melting points (group 2)

  melting point generally decreases

  • atomic radius increases
  • distance between nucleus and electrons increases 
  • weaker electrostatic forces of attraction - doesn't require much energy to remove electrons
• reactivity increases down the group
• products formed with reactions with water

  form metal hydroxide + hydrogen 
• Mg reaction with steam:

  vigorous reaction

  forms magnesium oxide
• solubility of hydroxides:

  more soluble down the group
• Mg(OH)2

  used in medicine

  • antacids - indigestion medicine
• Ca(OH)2

  used in agriculture

  • to neutralise soils
• solubility of sulfates

  less soluble down the group
• BaSO4

  used in medicine

  • ‘barium meal’ - X-rays
• tests for sulfates:

  • add HCl (acidify solution)
  • add barium chloride

  positive Test: white precipitate formed
• removal of sulfur dioxide:

  removing pollutants:

  • using calcium carbonate or calcium oxide
• extracting titanium

  TiO2 + 2 Cl2 + 2 C ----> TiCl4 + 2 CO

  TiCl4 + 2Mg ------> 2MgCl + Ti