chemical reactions of halogens

• What type of ions do halogens form?

  1- ions
• How do halogens form negative ions?

  By gaining an electron
• What are halide ions?

  Negative ions formed by halogens
• What happens to the oxidation number of halogens when they gain an electron?

  It decreases from 0 to -1
• What role do halogens play in oxidation reactions?

  They act as oxidising agents
• Why does reactivity decrease down group 7?

  Atomic radius increases and shielding increases
• What effect does increased atomic radius have on outer electrons?

  They are farther from the nucleus
• How does shielding affect the attraction between outer electrons and the nucleus?

  It weakens the attraction
• What happens to the ability of larger halogens to attract electrons?

  It becomes harder to attract electrons
• What is the relationship between oxidising power and reactivity in halogens?

  They decrease together down group 7
• Which halogen is the strongest oxidising agent?

  Fluorine
• Which halogen is the weakest oxidising agent?

  Iodine
• What occurs in displacement reactions involving halogens?

  A more reactive halogen displaces a less reactive halide
• What happens to the displacing halogen in a displacement reaction?

  It is reduced to form a halide ion
• What happens to the displaced halide in a displacement reaction?

  It is oxidised to form the halogen molecule
• What is the rule for halogen displacement reactions?

  • A halogen displaces any halide ion below it in group 7.
• What does the summary table of displacement reactions show?

  • Chlorine can oxidise bromide and iodide.
  • Bromine can oxidise iodide but not chloride.
  • Iodine cannot oxidise either bromide or chloride.
• What colour does the solution turn when bromide is displaced?

  Yellow
• What colour does the solution turn when iodide is displaced?

  Orange/brown
• What happens if no reaction occurs in a halogen displacement reaction?

  The solution remains colourless
• What are the visible colour changes in halogen displacement reactions?

  • Displacement of bromide: solution turns yellow.
  • Displacement of iodide: solution turns orange/brown.
  • No reaction: solution remains colourless.
• What are the results of halogen reactions with potassium salts?

  • Chlorine displaces bromide and iodide.
  • Bromine displaces iodide.
  • Iodine does not displace any halides.