• as you see the group 1 metals from up to down (lithium to francium), their density increases, their reactivity increases and their atomic radius increases. melting point and boiling point decrease tho.
• atomic mass increases faster than atomic volume for group 1 metals
• group 1 metals are soft
  • atoms with 1 valence electron
  • electrostatic force of attraction between sea of delocalised electrons and metal cation is weaker
  • weaker metallic bond
• unique properties of group 1 metals that are different from usual metals
  • low density
  • low melting point/boiling point
  • soft
  • highly reactive
• reactivity increases down group 1 because
  • atomic radii increases
  • valence electrons are further away from nucleus
  • electrostatic forces of attraction between valence electrons and nucleus is weaker
  • valence electrons are less strongly attracted to the nucleus