Group 7

• Reactivity

  Decreases as group 7 elements need to gain an electron. Atomic radius increases and attraction of nucleus decrease, so it is harder to gain electron.
• Halide ions

  • Good reducing agents as they donate electrons to the species being reduced while being oxidised
  • Reducing power increases down the group as electrons are easier to loose due to shielding and a larger atomic radius
• Oxidising agents

  • Halogens are good oxidising agents as they accept electrons from the species being oxidised while being reduced
  • Oxidising power decreases down the group as their ability to attract electrons decreases due to shielding and a greater atomic radius
• Test for halide ions

  Silver nitrate is used to test for halide ions

  
• Chlorine and water

  • Chlorine reacts with water to form Chloride ions and Chlorate(I) ions
  • This is a disproportionation reaction as chlorine is both oxidised and reduced
  • $Cl_2+$$H_2O\rightarrow\ ClO^-+$$Cl^-+$$2H^+$