Group 2 and the Halogens

• What is the trend in melting point down group 2?

  Decreases due to larger atomic radii, therefore less energy required to change state
• What coloured compounds do group 2 elements tend to form?

  Colourless compounds
• Describe the density of group 2 metals?

  Not dense, lightweight and easily cut
• Group 2 metals + water

  metal hydroxide + hydrogen
• Group 2 metals are also known as alkali metals - what does this tell you about the hydroxides they form?


  Group 2 metals form basic hydroxides/ bases
• What is the trend in group 2 hydroxide alkalinity?

  They become more alkaline down the group
• Trend in thermal stability of group 2 metals?

  Thermal stability increases down the group
• What group 2 compounds are used to treat indigestion?

  Carbonates - CO3 and hydroxides - (OH)2
• What is barium sulphate used for in medicine?

  Barium meals - used for X-rays
• What is disproportionation?

  A redox reaction where the same element is both oxidised and reduced
• Reaction between chlorine and water

  Cl2 + H2O -> HCl + HClO
• Why is water chlorinated?

  To kill bacteria
• Reaction between NaOH and chlorine

  2NaOH+Cl2>NaCl+NaClO+H2O
• Test for halides


  Add dilute nitric acid, silver nitrate solution, then ammonia solution
• Results of halide test

  Silver chloride - White in silver nitrate

  Silver bromide - cream in dilute NH3

  Silver iodide - Yellow in conc. NH3

  
• Why is nitric acid added when testing for halides with sodium hydroxide?

  Removes carbonate ions which could trigger false positive result for chloride ions