Group 2, Alkaline Earth Metals

• Describe the atomic radius down group 2

  atomic radius increases going down the group

  more protons so more nuclear charge

  but the shielding increases which is overweighted

  so the electrostatic attraction between outer electrons and nucleus decreases
• describe the ionisation energy going down group 2


  decreases going down group 2

  extra shells are added, outer electrons are further away from nucleus

  more shielding, so there is a weaker force of electrostatic attraction between nucleus and outer electrons

  so less energy needed to remove the electrons
• describe the melting point going down group 2

  generally decrease

  they form metallic structures where there is positive metal ions attracted to the delocalised electrons

  size of the metal ion increases , but number of delocalised electrons stay the same

  bigger ions means the distance between nucleus and outer electrons increases, so electrostatic forces of attraction decreases

  less energy needed to break bonds
• describe the reaction of water with group 2 metals

  forms bases - metal hydroxides

  reactivity increases going down the group

  atoms get larger, electrons get further away from the nucleus, and shielding increases, so electrostatic attraction between nucleus and outer electrons decreases

  less energy required to remove outer electrons
• describe the exception of magnesium reacting with water


  magnesium reacts slowly with cold water, but more vigorously with steam

  forms magnesium oxide instead of magnesium hydroxide, when reacts with steam
• describe solubility with group 2 hydroxides

  solubility increases down the group
• describe the solubility with group 2 sulfates

  solubility decreases going down the group
• what is the test for sulfates?

  add hydrochloric acid

  add barium chloride

  forms an insoluble white precipitate - barium sulfate

  
• why do you need to add hydrochloric acid specifically?

  to remove carbonates as this could precipitate and give a false result
• how is group 2 metals used for neutralisation?

  calcium hydroxide is used to neutralise acidic soils

  magnesium hydroxide is used to neutralise excess stomach acid

  barium sulfate helps identify problems with digestive system/tract - it lines the soft tissues eg. stomach, and the xrays absorb the barium sulfate

  barium compunds are toxic, but barium sulfate is insoluble so wont be absorbed into the blood
• describe the extraction of titanium using magnesium

  titanium ore is converted to titanium chloride by heating it with carbon and chlorine gas

  titanium chloride is passed through a fractionating column to increase its purity

  the purified titanium chloride is reduced using magnesium in 1000 degrees furnace

  TiCl4 +2Mg ———> Ti + 2MgCl2
• what is titanium used for

  it is light but strong - used for planes
• how would you remove sulfur dioxide using calcium carbonate/oxide?

  wet scrubbing - use an alkali to neutralise the SO2 in the flue gas

  involves dissolving CaCO3/CaO in water, and spraying it on acidic sulfur dioxide gas

  
• what are the group 2 hydroxide properties

  all white solids - contain OH

  the ions causes the substance to be alkaline
• When magnesium reacts with steam, what are 2 observations for this reaction?

  — bright white light

  — white / grey powder
• what is barium sulfate used for?

  — barium meal

  — x-rays of internal organs