2.02 Group II Metals

• Write an equation for the first ionisation energy of magnesium.

  Mg(g) → Mg+(g) + e-
• What happens to the first ionisation energy as you go down group 2? Why?

  Decreases.

  • Number of filled electron shells increase down the grouo
  • This causes increased shielding and atomic radius
  • Therefore there is a weaker force of attraction between outer electrons and nucleus
  • As a result, less energy is needed to remove electron
• How does reactivity with water change as you go down group 2?

  Increases (Mg least → Ba most)

  • Because outer electrons are further from the nucleus and there is more electron shielding, so electrons are lost more easily
• Write an equation for the reaction of barium and water.

  Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2
• Write an equation for the reaction of magnesium and steam.

  Mg(s) + H2O(g) → MgO(s) + H2
• What is the trend in hydroxide solubility down group 2?


  Increases down the group.

  • Mg(OH)2 is almost insoluble
  • Ba(OH)2 creates a strong alkaline solution
• What is the trend in sulphate solublity down the group?


  Decreases down the group.

  • MgSO4 is soluble
  • BaSO4 is insoluble
• What is the trend in melting point down group 2? Why?


  Decreases down group.

  • Sea of delocalised electrons are further away from the positive charge of the nucleus
  • Therefore weaker metallic bonds/forces of attraction which take less energy to weaken
• What is the trend in atomic radius down group 2?

  Increases as there are more occupied electron shells down the group
• Write the equations for the extraction of titanium using magnesium.

  TiO2 + 2Cl2 + C → TiCL4 + CO2

  TiCl4(l) + 2Mg(s) → 2MgCl2(s)+ Ti(s)
• What is Ca(OH)2 used for? Write an equation related to one of its uses

  Used to neutralise soil.

  • Ca(OH)2(aq) + 2HCl(aq) → 2H2O(l) + CaCl2(aq)
• What is Mg(OH)2 used for

  Milk of magnesia - antiacid to treat indigestion, heartburn, etc
• What is a use of BaSO4? Why is it safe?

  In barium meals to outline gut in x-rays

  • Ba2+ is toxic but is fine as barium sulphate is insoluble
• How can BaCl2 be used to test for sulfate ions?

  Add your sample with HCl to first acidify the solution, then add BaCl2.

  • White precipitate will form if sulfate ions are present.
  • Ba2+ + SO4-2 → BaSO4