group 1

• elements in the same group have similar chemical properties
• alkali metals are:

  • soft, easily cut
  • good conductors of heat and electricity
  • malleable
• alkali metals have low melting points and low densities so they float on water
• alkali metals have dull, grey surfaces due to oxidation but are shiny when freshly cut
• alkali metals are in group 1 because they have one electron in their outer shell
• alkali metals are very reactive because they only have one electron to lose in the outer shell
• reaction of lithium in water:

  • fizzes and moves quickly on surface of water
  • gets smaller until all of it has reacted and disappears
• lithium + water -> lithium hydroxide + hydrogen gas

  2Li + 2H2O -> 2LiOH + H2
• reaction of sodium in water:

  • melts to form a ball
  • fizzes rapidly
  • hydrogen produced burns with an orange flame
  • then sodium disappears
• sodium + water -> sodium hydroxide + hydrogen gas

  2Na + 2H2O -> 2NaOH + H2
• reaction of potassium in water:

  • melts into ball
  • moves very quickly on water surface
  • violent fizzing
  • hydrogen ignites instantly
  • metal is set on fire with lilac flame
  • small explosion
• potassium + water -> potassium hydroxide + hydrogen gas

  2K + 2H2O -> 2KOH + H2
• alkali metals react with water to produce an alkali solution: metal hydroxide and hydrogen gas
• order of alkali metals:

  • lithium
  • sodium
  • potassium
  • rubidium
  • caesium
  • francium
• alkali metals increase in reactivity down the group because:

  • number of electron shells increase
  • greater electron shielding + atomic radius increases
  • greater distance between positively charged nucleus and negative outer electron
  • weaker attraction
  • outer electron is more easily lost (less energy required)