group 2: alkaline earth metals

• why does atomic radius increase down group 2?

  1. electrons added to new shells, which are further from nucleus
  2. electron shield increases
  3. less electrostatic force of attraction between nucleus and outermostom electron
• why does first ionisation energy decrease down group 2?

  1. atomic radius increases
  2. electron shielding increase
  3. less energy required to remove outermost electron
• why does melting point decrease down group 2?

  1. all have metallic structure
  2. ionic radius increases
  3. electrostatic attraction between positive ions and delocalised electrons weakens
  4. less energy required to overcome metallic bonds
• what forms when group 2 metals react with water?

  metal hydroxide

  hydrogen
• why does reactivity increase down group 2?

  1. size of atom increases
  2. electrons being donated to further from nucleus
  3. more shielding
• what happens when beryllium reacts with water?

  beryllium doesn't react with water
• what happens when magnesium reacts with water?

  magnesium reacts slowly with water

  forms white precipitate

  Mg(s) + 2H2O (l) --> Mg(OH)2 (s) + H2(g)
• what happens when magnesium reacts with steam?

  magnesium reacts fastly with steam

  Mg(s) + 2H2) (g) --> MgO(s) + H2(g)
• what happens when calcium reacts with water?

  calcium reacts with cold water

  forms cloudy solution and slight white precipitate

  Ca(s) + 2H2O(l) --> Ca(OH)2(s) + H2(g)
• what happens when calcium reacts with excess water?

  Ca(OH)2 dissolves

  Ca(OH)2 --> Ca2+ + 2OH-
• what happened when strontium reacts with water?

  strontium reacts vigourously with water

  colourless solution formed

  Sr(s) + 2H2O(l) --> Sr(OH)2(aq) + H2(g)
• what happens when barium reacts with water?

  barium reacts vigourously with water

  borms colourless solution

  Ba(s) + 2H2O(l) --> Ba(OH)2(aq) + H2(g)
• what is the trend of solubility of hydroxide down group 2?

  increases
• what is magnesium hydroxide used for?

  neutralise stomach acid
• what is calcium hydroxide used for?

  neutralise acidic soil
• what is the trend of solubility of sulphates down group 2?

  decreases
• what is magnesium sulphate used for?

  epsom salt
• what is calcium sulphate used for?

  gypsum

  plaster
• what is barium sulphate used for?

  barium meal

  X-ray
• barium ions are toxic, how can they be used for barium meal?

  barium sulphate is insoluble so won't to bloodstream
• what is kroll process used for?

  titanium extraction
• what is kroll's process?

  1. TiO2 converted to TiCl4 at 900°C

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

  2. Magnesium used as reducing agent to reduce TiCl4 to titanium

  TiCl4 + 2Mg --> Ti + 2MgCl2
• what is the test for sulphate ions?

  1. acidify test solution with HCl
  2. add barium chloride solution
  3. positive result – white precipitate
• why is HCl added in the test for sulphate ions?

  removes impurities
• what is the flame test?

  1. dip nichrome wire into HCl (sterilise)
  2. hold wire in flame and observe colour change
  3. Ca2+ - brick red
  4. Sr2+ - red
  5. Ba2+ - pale green
• what is the test for magnesium and barium ions?

  Mg2+:

  1. add NaOH
  2. positive result – white precipitate

  Ba2+:

  1. Add H2SO4
  2. positive result – white precipitate