groups chem

• Ionisation Energy


  The energy needed to remove the outermost electron from an atom
• Group 1 (alkali metals)


  • Have one electron in their outermost principal quantum shell
  • Can form ionic compounds by donating their outermost electron to become a +1 ion
• Group 2 (alkali earth metals)


  • Have two electrons in their outermost principal quantum shell
  • Can form ionic compounds by donating their outermost electrons to become a +2 ion
• Going down the group

  The metals become more reactive
• First ionisation energy


  The energy needed to remove the first outer electron of an atom
• Second ionisation energy


  The energy needed to remove the second outer electron of an atom
• Reactivity of Group 1 metals

  • Increases as you go down the group
  • Atoms only need to lose 1 electron to form a +1 ion
  • Outermost electron gets further from nucleus, so less energy required to remove it
• Reactivity of Group 2 metals

  • Increases down the group for the same reasons as Group 1
  • Outermost electron gets further from nucleus, so less energy required to remove it
• Reaction of Group 1 metals with oxygen


  1. Form metal oxides

  2. Tarnish more rapidly as you go down the group
• Reactions of first three alkali metals with oxygen


  • Sodium, potassium, lithium
• Reaction of Group 1 metals with chlorine

  Form simple chlorides
• Reaction of Group 1 metals with water

  Get more vigorous as you descend the group
• Reactions of first three alkali metals with water

  • Sodium, potassium, lithium
• Reaction of Group 2 metals with oxygen


  1. Form metal oxides

  2. Some also form peroxides
• Reaction of Group 2 metals with water

  Form metal hydroxides and hydrogen gas
• Magnesium reacts extremely slowly with cold water
• Magnesium reacts vigorously with steam to form magnesium oxide and hydrogen
• Reaction of Group 2 metals with chlorine

  Form metal chlorides
• Metal oxide


  Formed when a metal reacts with oxygen
• Metal hydroxide


  Formed when a metal oxide reacts with water
• Reaction of metal oxides with dilute acids

  Form metal chlorides or metal sulfates
• Reaction of metal hydroxides with dilute acids

  Form metal chlorides or metal sulfates
• Reaction of Group 1 oxides with water


  Form colourless alkaline solutions
• Reaction of Group 1 hydroxides with dilute acid

  Form salts and water (neutralisation)
• Reaction of Group 2 oxides with water

  Form alkaline solutions, getting more alkaline going down the group
• Reaction of Group 2 oxides with sulfuric acid

  Form insoluble sulfates at the surface, preventing further reaction
• Reaction of Group 2 hydroxides with dilute acid

  Form colourless solutions of metal salts
• Solubility of Group 2 hydroxides increases going down the group
• Solubility of Group 2 sulfates decreases going down the group
• Group 1 compounds are all soluble in water, so they don't produce precipitates when testing for cations - you need to use flame tests instead
• Solubility of Group 2 hydroxides

  Increases going down the group, making the solutions more alkaline
• Solubility of Group 2 sulfates

  Decreases going down the group
• Group 1 compounds are all soluble in water, so they do not produce precipitates when testing for cations
• Group 1 hydroxides are more soluble than Group 2 hydroxides
• At 25°C, the solubility of Ba(OH)2 is 4.68 g/100 cm3, while the solubility of KOH is 121 g/100 cm3
• Thermal decomposition


  The breakdown of a compound into two or more different substances using heat
• Thermal decomposition of carbonates

  1. Reactant: Metal carbonate

  2. Products: Metal oxide + Carbon dioxide
• Lithium carbonate decomposes when heated, while the rest of the Group 1 carbonates don't decompose at Bunsen temperatures
• The decomposition temperatures of carbonates increase going down Group 2
• Thermal decomposition of nitrates


  1. Reactant: Metal nitrate

  2. Products: Metal oxide + Oxygen + Nitrogen dioxide (for Group 1)

  3. Metal nitrite + Oxygen (for Group 1 except lithium)