Group 2 alkaline metals

• Going down group 2 , atomic radius increases due to having more shells of electrons. Shielding doesn't effect it as you go down the group
• The first ionisation energy decreases as you go down group 2 because even though nuclear charge increases, shielding also increases so electrostatic attraction between nucleus and outer electrons is weaker
• Melting and boiling points decreases as you do down the group due to shielding increasing which causes the metallic bond to be weaker and less energy is required to break the electrostatic forces. For magnesium, it has a lower melting point then expected due to variation in how it's atoms pack in the metallic crystal
• Reactions of group 2

  • Group 2 elements react with oxygen to make metal oxides
  • Group 2 elements react with water to form metal hydroxide and hydrogen gas. E.g. Sr (s) + 2H2O (l) --> Sr ( OH )2 (aq) + H2 (g)
  • Fizzing occurs, the metal dissolves and solution heats up
  • For calcium a white precipitate forms
• Reaction of magnesium with water

  Magnesium reacts very slowly with water but it reacts quickly with steam and gives different products

  Mg (s) + H20 (g) --> MgO (s) + H2 (g)
• Solubility of group 2 compounds ( group 2 hydroxides )

  Solubility increases as you go down the group so Mg(OH)2 would be sparingly soluble while Ba(OH)2 is soluble. As well as pH increasing since more metal hydroxide dissolves, so more greater concentration of hydroxide ions.
• Solubility of group 2 sulfate

  Solubility decreases as you go down the group so MgSO4 is very soluble while BaSO4 is insoluble
• Application of group 2 hydroxides

  • Magnesium hydroxide is used as medicine as a laxative and relieves acid indigestion. Due to having low solubility so it doesn't hurt the oesophagus
  • Calcium hydroxide is used in agriculture as it raise pH of soil
  • Barium sulfate is used at a radiocontrast agent to make X-ray images of digestive system as it's insoluble
  • CaO or CaCO3 to remove SO2
• Extraction of Titanium

  Group 2 elements are used as the metal in the displacement reactivity to obtain titanium

  Stage 1 ( C = Coke )

  • At 900 °c , TiO2 (s) + 2Cl2 (g) + C --> TiCl4 (l) + CO2 (g)
  • Then TiCl4 is purified by fractional distillation in Ar

  Stage 2

  • At 500 °c TiCl4 (l) + 2Mg (s) --> Ti (s) + 2MgCl2 (s)
• Test for sulfate ions

  BaCl2 is used due to BaSO4 high insolubility.

  • First add 5cm^3 of unknown solution containing sulfate ions in a test tube using measuring cylinder
  • Next acidify it with dilute hydrochloric acid to prevent the precipitation of other insoluble ions such as carbonate
  • Then add few drops of barium chloride solution
  • The positive result is white precipitate of barium sulfate forming