Group 2

• as you move down the periodic table the atomic radius increases as more shells are added
• first ionisation energy decreases down group 2 as there is an increase in atomic radium and shielding
• reactivity increases down group 2 as they loose their outer electrons more easily
• melting points generally decrease down group two as the number of delocalised electrons and the charge of the ion (2+) stays the same but the atomic radius increases.

  magnesium does not follow this trend as crystal structure is different
• when group 2 elements react with water they give a metal hydroxide and hydrogen
• the solubility of group 2 compounds depends on the anion in the compound. generally compounds that contain singly charged ions (eg. OH-) increase in solubility down the group and doubly charged ions (eg. SO4 2-) decrease in solubility

  
• Mg(OH)2 is sparingly soluble
• most sulphates are soluble in water but barium sulphate (BaSO4) is not
• test for sulphate ions


  utilises the fact that BaSO4 is insoluble in water

  • add HCl and barium chloride (BaCl2) to solution containing sulphate ions
  • white precipitate forms

  the barium chloride must be acidified by HCl as it removes any sulphites or carbonates which would also produce a white precipitate
• barium sulphate is also used to view soft tissue as X rays cannot pass through it. other barium compounds cannot be used for this as barium ions are poisonous
• extraction of titanium


  magnesium is used to extract titanium from its ore

  titanium oxide (TiO2) is converted to titanium chloride (TiCl4) and is then reduced by magnesium
• removal of sulphur dioxide from flue gases


  burning fossil fuels produces sulphur dioxide

  the acidic sulphur dioxide can be removed by reacting it with an alkali

  calcium carbonate/limestone (CaCO3) and calcium oxide (CaO) can both be used for this

  a slurry is made by mixing it with water and this reacts to produce a solid waste product, calcium sulphite
• calcium hydroxide (Ca(OH)2) is used in agriculture to neutralise acidic soils