3.2.4: Properties of Period 3 Elements & Their Oxides

• The reactions of P3 elements in air:

  • A - vigorous
  • B - slow
  • C - slow
  • D - spontaneously combusts
  • E - burns steadily

  
• Explain the trend in MP of the P3 oxides

  • Ionic oxides have higher MP | covalent oxides have lower MP
  • Al2O3 has lower MP due to exhibiting covalent character -> differences in electronegativity not as large between Al & O compared to Mg & O -> O2- does not attract electrons as strongly in bond -> not purely ionic interactions/attractions
  • SiO2 has higher MP due to covalent macromolecular structure -> covalent bonds strong
  • P4O10 & SO2 lower MP due to (only) VDW & dipole-dipole forces between molecules -> weak

  
• Reaction of Na with H2O

  • Na + H2O -> NaOH + H2
• Reaction of Mg + H2O (l.)

  • Mg + H2O -> Mg(OH)2 + H2
• Reaction of Mg + H2O (g.) / STEAM

  • Mg + H2O -> MgO + H2
• Reaction of Na with oxygen:

  • 2 Na + 1/2 O2 -> Na2O
• Reaction of Mg with oxygen:

  • Mg + 1/2 O2 -> MgO
• Reaction of Al with oxygen:

  • 4 Al + 3 O2 -> 2 Al2O3
• Reaction of Si with oxygen:

  • Si + O2 -> SiO2
• Reaction of P with oxygen:

  • P4 + 5 O2 -> P4O10
• Ionic oxides

  • Alkaline / basic
• Reaction of the ionic oxides with H2O:

  • Na2O + H2O -> NaOH
  • MgO + H2O -> Mg(OH)2
• Non-metal (covalent) oxides

  • Acidic
• Reactions of the non-metal (covalent) oxides with H2O:

  • P4O10 + 6 H2O -> 4 H3PO4
  • SO2 + H2O -> H+ + HSO3- / H2SO3
• Reaction of S in oxygen:

  • S8 + 8O2 -> 8 SO2
• SiO2 will react with bases despite insolubility in H2O

  • SiO2 + NaOH -> NaSiO3 + H2O
• Al2O3 exhibits COVALENT character with ionic bonding -> AMPHOTERIC

  
  

  Reaction with acids:

  • Al2O3 + H2SO4 -> Al2(SO4)3 + H2O
  • Al2O3 + 6 HCl -> 2 AlCl3 + 3 H2O

  
  

  Reaction with bases:

  • Al2O3 + 2 NaOH + 3H2O -> 2 NaAl(OH)4
  • Al2O3 + 2 KOH + 3H2O -> 2 KAl(OH)4
• This depicts the structure of what acid?

  H3PO4 (phosphoric acid)

  
• This depicts the structure of what anion?

  PO4 3- (phosphate ion)

  
• This depicts the structure of which anion?

  HPO4 2- (hydrogenphosphate ion)
• This depicts the structure of what anion?

  HPO4 2- (hydrogenphosphate)