group 7

• What is Group 7 of the periodic table known as?

  Halogens
• Which elements are included in Group 7?

  Fluorine, chlorine, bromine, iodine
• Why do all Group 7 elements have similar chemical properties?

  They have 7 electrons in their outer shell
• What type of molecules do halogens exist as?

  Diatomic molecules
• What happens when halogens share one pair of electrons?

  Both atoms achieve a full outer shell
• How do the melting and boiling points of halogens change down Group 7?

  They increase as you go down the group
• What is the state and color of chlorine at room temperature?

  Fairly reactive, poisonous, green gas
• What is the state and color of bromine at room temperature?

  Poisonous, red-brown liquid
• What is the state and color of iodine at room temperature?

  Dark grey crystalline solid
• How can you predict the properties of astatine based on iodine?

  Astatine would be a dark-colored solid
• How can you test for chlorine gas?

  Using damp blue litmus paper
• What happens to damp blue litmus paper when exposed to chlorine?

  It will bleach the litmus paper
• What is the physical state of iodine (I₂) at room temperature?

  Dark grey crystalline solid
• What happens to iodine when it is heated?

  It gives off a purple vapour
• How does the melting point of halogens change down the group?

  It increases down the group
• What can be predicted about astatine based on iodine's properties?

  Astatine would be a dark-coloured solid
• How can you test for chlorine gas?

  Using damp blue litmus paper
• What happens to damp blue litmus paper when exposed to chlorine?

  It turns white and may turn red first
• Why does damp blue litmus paper turn red when exposed to chlorine?

  Chlorine solution is acidic
• What trend is observed in the reactivity of halogens down Group 7?

  Reactivity decreases going down the group
• Why do halogens become less reactive down the group?

  It gets harder to attract an extra electron
• What do halogens react with to form metal halides?

  They react with some metals
• What do halogens form when they react with hydrogen?

  They form hydrogen halides
• What happens when hydrogen halides dissolve in water?

  They form acidic solutions
• How can the reactions of chlorine, bromine, and iodine be used?

  To predict reactions of fluorine and astatine
• What are the general properties of halogens?

  • They are one electron short of a full shell
  • They have similar reactivity trends
  • They can form salts with metals
• What group do halogens belong to in the periodic table?

  Group 7
• What happens in a displacement reaction involving halogens?

  A more reactive halogen displaces a less reactive one
• What is a displacement reaction?

  It is when a more reactive element displaces a less reactive one
• What type of reactions do halogens undergo?

  Redox reactions
• In redox reactions, what happens to halogens and halide ions?

  Halogens gain electrons; halide ions lose electrons
• If chlorine is added to potassium bromide solution, what will happen?

  Chlorine will displace bromine
• What is the result of chlorine displacing bromine in potassium bromide solution?

  Potassium chloride is formed
• What color change occurs when bromide ions are oxidized to bromine?

  The solution turns orange
• How can displacement reactions be used to show reactivity trends of halogens?

  • Measure halide salt solution in a test tube
  • Add halogen solution and shake gently
  • Observe color change for a reaction
  • No color change indicates no reaction
  • Repeat with different halide salts and halogens
• What happens when chlorine water is added to potassium bromide solution?

  • Chlorine displaces bromine
  • Solution turns orange due to bromine
  • Potassium chloride is formed
• What is the reactivity trend of halogens in Group 7?

  • Reactivity decreases down the group
  • Chlorine displaces bromine and iodine
  • Bromine displaces iodine
  • Iodine cannot displace chlorine or bromine
• What color change occurs when iodine is added to potassium iodide solution?

  No color change occurs
• If a student adds a halogen solution to potassium iodide and the solution turns brown, what should they conclude?

  The halogen is likely bromine or iodine
• What should a student do to identify the halogen solution after observing a color change?

  Test with different halide salts