Halogens

• Electronegativity decreases down group 7
• What colour are the following ?

  Flourine - pale yellow

  Chlorine - green

  Bromine - red-brown

  Iodine - grey
• What are the states of the following at room temperature ?

  Flourine- gas

  Chlorine- gas

  Bromine- liquid

  Iodine- solid
• They’re non polar and have a low solubility in water
• They easily dissolve organic compounds e.g hexane
• colour of the following in water?

  chlorine- virtually colourless

  bromine- yellow/orange

  iodine- brown
• explain why halogens get less reactive down the group

  • they react by gaining and electron (reduction) so they’re oxidizing agents
  • down the group atoms get larger so the outer electron is further from the nucleus and there is increased shielding so less attraction from the positive nucleus.
  • This means it’s harder for the atom to attract an electron so reactivity decreases down the group.
  • Electronegativity also decreases down the group due to more electron shells which increase the distance between the nucleus and the bonding electrons
• Melting and boiling point increase down the group
• • As you go down group 7 there’s an increase in electron shells.
  • This means London forces get stronger between halogen molecules.
  • This makes it harder to overcome Intermolecular forces so melting and boiling points increase.

  The chemistry of fluorine and astatine is hard do study as fluorine is a toxic gas and astatine is radioactive and decays quickly. You can predict they’re behavior by looking at that of the other halogens and fitting them into those trends.
• Halogens can displace halide ions from solution.

  e.g Cl2 (aq)+ 2KBr (aq) —> KCl (aq) + Br2 (aq)

  chlorine displaces bromine and iodine

  Bromine displaces iodine but not chlorine

  Iodine displaces neither
• Halogen halide reaction Is a?

  redox reaction
• Halogens only displace halides that are below them on the periodic table