group 7

• colours and states

  F - yellow gas

  Cl - green gas

  Br - dark brown liquid

  I - grey solid

  At - black solid
• Melting and Boiling point

  increases going down

  • more electrons=more shells=stronger London forces
  • stronger induced dipole-dipole interactions/London forces between molecules
  • more energy required to break these strong intermolecular induced dipole-dipole interactions
• why does reactivity decrease?

  electrons less able to be reduced (less nuclear attraction)
• DISPLACEMENT REACTIONS

  reactions where the more reactive element displaces the less reactive element in aqueous solution of halide ions
• DISPROPORTIONATION REACTION

  a reaction where the same element is both oxidised and reduced
• disproportionation reactions


  chlorine with COLD AND DILUTE AQUEOUS sodium hydroxide

  Cl2 + 2NaOH -> NaClO + 2NaCl + H2O - the CLO$\ ^-$ is used to make bleach (chlorate)

  NaClO3 is formed when chlorine reacts with hot and concentrated sodium hydroxide

  chlorine and water

  Cl2 + H2O -> HClO + HCl

  the chloric acid is used to kill bacteria in water

  TOXIC IF INGESTED

  PRODUCES SOME CARCINOGENIC CHLORINATED HYDROCARBONS (HCl, Cl)