group 7

• What type of elements are group 7 elements?

  Highly reactive non-metals
• Why do group 7 elements need to gain an electron?

  To form a 1- ion and achieve stability
• What happens to the atomic radius of group 7 elements down the group?

  It increases
• Why does reactivity decrease down group 7 elements?

  Due to increased atomic radius and shielding
• What is the trend in first ionisation energy for group II metals?

  It decreases down the group
• What causes the boiling point of group 7 elements to increase down the group?

  Stronger van der Waals forces due to larger Ar
• What is the state of fluorine at room temperature?

  Gas
• What is the oxidising power of halogens?

  Good oxidising agents
• How does oxidising power change down the group of halogens?

  It decreases
• What happens to halide ions in terms of reducing power down the group?

  Reducing power increases down the group
• What are the redox reactions with H2SO4 for halide ions?

  1. Fluoride and Chloride ions
  2. Bromide ions
  3. Iodide ions
• What is the significance of the greater reducing power of halides?

  It allows them to reduce more species
• What is used to test for halide ions?

  Acidified silver nitrate
• What do the different coloured precipitates indicate when testing halide ions?

  Different halide ions present
• What precipitate forms with chloride ions and silver nitrate?

  White precipitate (AgCl)
• What precipitate forms with bromide ions and silver nitrate?

  Cream precipitate (AgBr)
• What precipitate forms with iodide ions and silver nitrate?

  Yellow precipitate (AgI)
• What happens to the precipitate of chloride ions when dilute ammonia is added?

  Precipitate dissolves
• What happens to the precipitate of bromide ions when concentrated ammonia is added?

  Precipitate dissolves
• What happens to the precipitate of iodide ions when concentrated ammonia is added?

  No change occurs
• What do chlorate(I) ions (ClO-) produce when chlorine reacts with cold water?

  Chlorate(I) ions and chloride ions
• What type of reaction occurs when chlorine reacts with cold water?

  Disproportionation reaction
• What happens to chlorine in the disproportionation reaction with cold water?

  It is both oxidised and reduced
• What does chlorine produce when it decomposes water in the presence of UV light?

  Oxygen and hydrochloric acid

  
• What is the role of chlorine in water treatment processes?

  To kill bacteria
• What is produced when chlorine is mixed with cold, aqueous sodium hydroxide?

  Sodium hypochlorite
• What is the test for sulfate ions (SO4^2-)?

  Using BaCl2 to form a white precipitate
• How can hydroxide ions (OH-) be identified?

  Using red litmus that turns blue
• What happens when an acid is added to carbonate ions (CO3^2-)?

  Effervescence occurs and CO2 is released
• How can CO2 be confirmed after reacting with carbonate ions?

  By bubbling through limewater which turns cloudy
• What are the flame test colors for group 2 cations?

  • Calcium (Ca2+): Brick red
  • Strontium (Sr2+): Red
  • Barium (Ba2+): Pale green
• How can ammonium ions (NH4+) be tested for?

  By holding red litmus over the substance
• What happens when NaOH is added to test for ammonium ions?

  Ammonia gas is produced