Group 7 (Halogens) and Group 0 (Noble gases)

• Halogens

  • Exist as pairs called diatomic molecules - they do this by sharing electrons and forming a covalent bond
  • Melting points and boiling points increase as you go down the group
  • Reactivity decreases as you go down the group
• Why does the reactivity decrease as you go down Group 7?

  As you go down the group, the outermost shell becomes further away from the nucleus so the attractive force to pull another electron to become stable becomes weaker. And if the halogen can't attract an electron it can't react
• Group 7

  • Halogens form ionic bonds with metals
• Group 7

  • Displacement reactions- when a more reactive halogen displaces a less reactive one
  • More reactive halogens will always displace less reactive ones
• Noble gases

  • Exist as colourless gases
  • They have a full outer shell so they can't really react
  • Exist as single atoms
  • Boiling points increase as you go down the group