period 3

• 2Na (s) + 2H2O (l) -> 2NaOH (aq) + H2 (g)

  • reacts vigourously, fizzes, floats, colourless solution
  • very alkaline
• Mg (s) + 2H2O (l) -> Mg(OH)2 (aq) + H2 (g)


  • reacts very slowly
  • slightly alkaline as it is not very soluable
• Mg (s) + H2O (g) -> MgO (s) + H2 (g)

  • reacts vigorously, white bright light
  • white light
• phosphorus oxide is P4O10
• Na2O

  • ionic
  • alkaline
  • white solid
• MgO

  • ionic
  • white solid
  • slightly alkaline
• SiO2

  • macromolecular
  • acidic
  • white solid
• P4O10

  • simple covalent
  • acidic
  • white solid
• SO3

  • simple covalent
  • acidic
  • colourless liquid
• SO2

  • simple covalent
  • acidic
  • gas
• Na flame test

  yellow
• Mg flame test

  white
• P flame test

  white
• S flame test

  blue
• Na in air


  vigorous
• Mg in air

  vigorous
• Al in air

  slow
• Si in air

  slow
• P in air

  spontaneous combustion
• S in air

  burns steadily
• P4O10 + 6H2O -> 4H3PO4 (phosphoric acid)
• SO2 + H2O -> H2SO3 (sulfurous acid)
• SO3 + H2O -> H2SO4 (sulfuric acid)
• MgO + H2O -> Mg(OH)2
• Na2O + H2O -> 2NaOH
• Al2O3 + 3H2SO4 -> Al2(SO4)3 + H2O
• Al2O3 + 2NaOH -> 2NaAl(OH)4 + H2O
• ranking melting points

  1. MgO
  2. Al2O3
  3. SiO2
  4. Na2O
  5. P4O10
  6. SO3
  7. SO2
• Al2O3

  • partially ionic, partially covalent (due to the little difference in electronegativity between Al and O)
  • white solid
  • amphoteric
• why melting point MgO > Al2O3

  • the difference in electronegativity between Al and O is a lot smaller than between Mg and O