Alkali metals

• Alkali Metals


  Group 1 of the periodic table, on the left
• Alkali metals


  • Lithium (Li)
  • Sodium (Na)
  • Potassium (K)
  • Rubidium (Rb)
  • Caesium (Cs)
  • Francium (Fr)
• Alkali metals


  • Have 1 electron in their outer shell
  • Can easily obtain a full outer shell by losing 1 electron
  • Have similar physical and chemical properties
  • Form positive ions with a +1 charge
• Reactivity of alkali metals

  Increases down the group
• Reason for increasing reactivity

  • Size of the element's atoms and number of full electron shells increases down the group
  • Electron in the outer shell gets further away from the nucleus and is shielded by more electron shells
  • The further away an electron is from the positive attraction of the nucleus, the easier it can be lost in reactions
• General properties of alkali metals

  • Shiny when freshly cut
  • Good conductors of heat and electricity
  • Soft and can be cut by a knife (softness increases down the group)
  • Low density - lithium, sodium and potassium float on water
  • Low melting and boiling points
• Density of alkali metals


  Generally becomes more dense down the group, but the trend is not perfect
• Melting point of alkali metals

  Decreases down the group
• Reason for low melting points

  Alkali metals only have 1 electron in their outer shell, not much heat energy is needed for this electron to be lost
• Reaction of alkali metals with air

  1. Forms metal oxides

  2. Produces a layer of black oxide on the surface of the metal (tarnish)

  3. Speed of reaction increases down the group
• Alkali metals are stored in oil to prevent them from reacting with air and tarnishing
• Reaction between an alkali metal and air

  Oxidation reaction
• Flame colour when alkali metals are heated and added to oxygen

  • Lithium - red flame
  • Sodium - orange flame
  • Potassium - lilac flame
• All alkali metals react readily with water, the reaction becomes more vigorous down the group and creates a lot of heat
• Reason for the group 1 elements being called alkali metals


  The reaction creates alkaline hydroxide ions
• Reaction of lithium with water

  1. 2Li (s) + 2H2O (l) → 2LiOH (aq) + H2 (g)

  2. Lithium fizzes and moves around slowly across the surface of the water
• Reaction of sodium with water

  1. 2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

  2. Sodium fizzes more than lithium, moves quickly across the surface of the water, melts as it reacts, and becomes spherical and shiny

  3. The hydrogen sometimes catches fire because of the heat from the reaction
• Reaction of potassium with water

  1. 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)

  2. Potassium burns with a lilac flame and the hydrogen catches fire immediately, moves across the surface of the water very quickly, and melts with the heat of the reaction
• Reaction of alkali metals and chlorine

  Forms metal chlorides
• Reaction of lithium and chlorine

  2Li (s) + Cl2 (g) → 2LiCl (s)
• Reaction of sodium and chlorine

  2Na (s) + Cl2 (g) → 2NaCl (s)
• Uses of lithium


  • Medical treatment - lithium carbonate
  • Submarines and space vehicles - lithium hydroxide
  • Batteries - elemental lithium and lithium compounds
  • Alloys with other metals
• Uses of sodium


  • Sodium chloride - table salt
  • Street lights - sodium vapour
  • Nuclear reactors - coolant
  • Sodium compounds in household products
• Uses of potassium


  • Fertilizers
  • Fireworks and explosives
  • Food preservation