Group 7

6.6 Recall the colours and physical states of chlorine, bromine and iodine at room temperature
  • Chlorine is a yellow-green gas
  • Bromine is a red-brown liquid
  • Iodine is a purple solid
6.7 Describe the pattern in the physical properties of the halogens, chlorine, bromine and iodine, and use this pattern to predict the physical properties of other halogens
  • There is a trend in state from gas to liquid to solid down the group
6.8 Describe the chemical test for chlorine
  • Uses litmus paper
    • When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white
6.9 Describe the reactions of the halogens, chlorine, bromine and iodine, with metals to form metal halides, and use this pattern to predict the reactions of other halogens
  • They react with metals to form ionic compounds in which the halide ion carries a -1 charge.
  • Reaction is less vigorous as you move down group 7
  • A more reactive halogen can displace a less reactive in an aqueous solution of its salt.

E.g. Chlorine will displace bromine if we bubble the gas through a solution of potassium bromide:

Chlorine + Potassium Bromide à Potassium Chloride + Bromine

6.10 Recall that the halogens, chlorine, bromine and iodine, form hydrogen halides which dissolve in water to form acidic solutions, and use this pattern to predict the reactions of other halogens
6.11 Describe the relative reactivity of the halogens chlorine, bromine and iodine, as shown by their displacement reactions with halide ions in aqueous solution, and use this pattern to predict the reactions of astatine
  • As you go down the group, the element is less reactive because the higher the energy level of the outer electrons, the less easily electrons are gained (attracted to the positive nucleus.)
6.12 (HT only) Explain why these displacement reactions are redox reactions in terms of gain and loss of electrons, identifying which of these are oxidised and which are reduced
  • More reactive halogen displaces the less reactive one, forming a negative ion itself, therefore being reduced as it gains electrons
    • Thus, the less reactive halogen that is displaced is oxidised as it gains these electrons
6.13 Explain the relative reactivity of the halogens in terms of electronic configurations