Group 7

• Trend in atomic radius down group 7

  • Increases down the group
  • More shells present
• Trend in reactivity of group 7 elements

  • Decreases
  • Due to increased shielding outer electrons are further from the positive nucleus, so less attraction and is harder to gain an electron
• Trend in ionisation energy in group 7

  • Decreases down the group
  • Due to increased shielding
• Trend in boiling points of group 7

  • Simple molecular covalent
  • Only has van der waals forces which are weak and easily to break
  • Boiling point and melting point increases down the group
• Oxidising power of group 7

  1. Iodine
  2. Bromine
  3. Chlorine
  4. Fluorine
• Reducing power of group 7

  1. Fluorine
  2. Chlorine
  3. Bromine
  4. Iodine
• Redox reaction of NaF or NaCl with H2SO4

  • NaX + H2SO4 -> NaHSO4 + HX
• Redox reaction of NaBr with H2SO4

  • NaBr + H2SO4 -> NaHS4 + HBr
  • 2HBr + H2SO4 -> Br2 + SO2 + 2H2O
• Redox reactions between NaI with H2SO4

  • NaI + H2SO4 -> NaHSO4 + HI
  • 2HI + H2SO4 -> I2 + SO2 + 2H2O
  • 6HI + SO2 -> H2S + 3I2 + 2H20
• Testing for the presence of Cl- ions

  • Add AgNo3 - white ppt
  • Add dilute NH3 - redissolves
  • Add concn NH3 - redissolves  
• Testing for the presence of Br- ions

  • Add AgNO3 - cream pot
  • Add dilute NH3 - n.v.c
  • Add concn NH3 - redissolves
• Testing for I- ions

  • Add AgNO3 - yellow ppt
  • Add dilute NH3 - n.v.c
  • Add concn NH3 - n.v.c
• Reaction of Cl2 with water

  • Cl2 + H2O -> ClO- + Cl- + 2H+
• Reaction of Cl2 with H2O in the presence of UV light

  • 2Cl2 + 2H2O -> HCl + O2
• Equation for the production of bleach

  • 2NaOH + Cl2 -> NaClO + NaCl + H2O
• Why is Chlorine used in water treatment but only in small quantities?

  • Chlorine kills any bacteria/microorganisms in the water
  • It's toxic in large quantities