Group 7

• What are group 7 elements called?

  Halogens
• How many electrons do group 7 elements have in their outer shell?


  7
• Are halogens metals or non metals?


  Nonmetals
• What is a displacement reaction in Group 7 elements?

  • More reactive Group 7 elements can replace less reactive ones in a compound.
  • Example: Chlorine + potassium bromide → potassium chloride + bromine
• How does reactivity change down Group 7?

  Reactivity decreases down Group 7
• What are the key physical properties of halogens?

  • Non-metals
  • Toxic and corrosive
  • Coloured
  • Low melting and boiling points (compared to metals)
  • Exist as diatomic molecules (e.g., Cl₂)
• What is the trend in melting and boiling points down Group 7?

  • Melting and boiling points increase as you go down the group.
  • This is because intermolecular forces get stronger, requiring more energy to break.
• What is the trend in reactivity down Group 7?

  • Reactivity decreases down the group
  • This is because the outer shell is further from the nucleus, so it’s harder to gain an electron
• What type of ions do halogens form and why?

  Halogens gain 1 electron to form -1 ions because they have 7 electrons in their outer shell.
• What happens when halogens react with metals?

  • They form ionic compounds called metal halides (e.g., sodium chloride)
  • The metal loses electrons and the halogen gains one.
• What happens when halogens react with non-metals?

  They form covalent compounds by sharing electrons (e.g., hydrogen chloride, HCl).
• What is a displacement reaction in Group 7?

  A more reactive halogen displaces a less reactive halogen from an aqueous solution of its salt.
• What is the colour change in a displacement reaction?

  • When a halogen is displaced, a new colour may appear in solution (e.g., brown if bromine is formed)
• Why does chlorine displace bromine but not fluorine?

  Chlorine is more reactive than bromine but less reactive than fluorine, so it can only displace bromine or iodine, not fluorine.
• Why are halogens stored in oil in the lab?

  • To prevent them from reacting with air or moisture, as they are very reactive and toxic.