chemistry: group 17

• • fluorine pale yellow gas
  • chlorine green yellow gas
  • bromine red brown liquid
  • iodine shiny black solid
  • astatine black solid
• solubility of group 7 elements decreases
• boiling point increases down the group
• iodine vapors = purple colour

  iodine solid = shiny black

  iodine in water = red brown
• all hydrogen halides gases are white fumes

  all hydrogen halides acids are colourless solutions
• boiling point increases

  volatility decreases down the group

  no of polarisable electrons increase down the group

  more id id forces

  more energy required to overcome them
• oxidising power decreases

  reducing power increases
• oxidising power decreases

  atomic radius increases

  force of attraction between nucleus and valence electrons decreases

  easier to lose the electron than to gain them.
• thermal stability of hydrogen halides decreases down the group

  bond energy decreases

  atomic radius of halogens increase

  hydrogen halide bond becomes longer and weaker as it is further away from the nucleus

  bonding electrons experience less nuclear force of attraction so are easily broken
• no reaction when HF and HCl are heated

  HBr produces H and Br gas ( red brown vapours)

  HI produces H and I ( purple vapours )
• Displacement reactions of halogens

  each halide ion can be oxidised by the more reactive halogen
• Test for halides with AgNO3

  • NaCl = white ppt
  • NaBr = cream ppt
  • NaI = yellow ppt

  Dilute aq NH3

  NaCl = soluble

  NaBr = partially soluble

  NaI = insoluble
• no further reaction with H2SO4 and HCl becauses H2SO4 is not a strong enough oxidising agent to oxidides HCl into Cl gas.