2.3 Group 7(17) the halogens

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The halogens in Group 7 are very reactive non-metals.
Trends in their physical properties are examined and explained.
Fluorine is too dangerous to be used in a school laboratory but the reactions of chlorine are studied.
Challenges in studying the properties of elements in this group include explaining the trends in ability of the halogens to behave as oxidising agents and the halide ions to behave as reducing agents.

  • Trends in halogen physical properties - General properties Halogens: F2           pale yellow-green gas Cl2          pale green gas Br2          orange/brown liquid I2           black/grey solid (purple fumes following sublimation) At2         (radioactive element,  further knowledge about its chemistry is generally excluded from A2 syllabi) Halide ions: F−        
  • Uses of chlorine and chlorate(I) - The reaction of chlorine with water to form chloride ions and chlorate(I) ions. The reaction of chlorine with water to form chloride ions and oxygen. Appreciate that society assesses the advantages and disadvantages when deciding if chemicals should be added to water supplies. The use of chlorine in water treatment. Appreciate that the benefits to health of water treatment by chlorine outweigh its toxic effects. The