Properties of period 3 elements & their oxides

• What is the reaction between sodium and water

  Na + H2O —> NaOH + H2

  fizzes, floats, it moves, it melts
• reaction of magnesium with water

  cold water: Mg +H2O(l) —> Mg(OH)2 + H2

  very slow

  steam : Mg + H2O(g) —> MgO +H2

  fast, bright white light, white solid
• reaction of chlorine with water

  Cl2 + H2O <=> HCl +HClO

  in sunlight : 2Cl2 +2H2O —> 4HCl + O2
• sodium with oxygen

  2Na + 1/2O2 —> Na2O

  burns with orange flame and produces a white solid
• magnesium with oxygen

  Mg + 1/2O2 —> MgO

  bright white flame
• oxygen with aluminium

  2Al + 3/2O2 —> Al2O3

  white solid
• silicon with oxygen

  Si + O2 —> SiO2

  white flame

  white solid
• phosphorus with oxygen

  P4 + 5O2 —> P4O10

  very bright white flame
• sulfur and oxygen

  S + O2 —> SO2

  blue flame

  choking gas
• bonding and structure and meting point of Na2O

  ionic lattice

  strong electrostatic forces of attraction
• structure and bonding in MgO

  Ionic lattice

  higher melting point than Na2O as its a smaller ion and has a higher charge
• structure and bonding in Al2O3

  ionic (with some degree of covalent character)

  • the aluminium cation is smaller so get closer to the oxide ions
  • Al3+ can distort the electron cloud
• structure and bonding of SiO2, P2O10, SO2 and SO3

  SiO2 - giant covalent

  P4O10 - covalent molecular

  SO2 - Covent molecular

  SO3 - Covent molecular
• Na2O with water

  Na2O + H2O —> 2NaOH

  Na+ and O2- ions dissolve in water and O2- ions react with water to form OH- ions (O2- +H2O —> 2OH)

  pH = 14
• MgO with water

  MgO + H2O –> Mg(OH)2

  sparingly soluble

  pH= 9-10
• Al2O3 with water

  insoluble

  strong ionic bonds holding lattice together

  pH = 7
• SiO2 with water

  Insoluble

  covalent bonds holding the silicon + oxygen atoms together

  pH = 7
• P4O10 with water

  P4O10 + 6H2O —> 4H3PO4

  reacts violently

  pH = 1-2
• SO2 with water

  SO2 + H2O —> H2SO3

  pH =2-3
• SO3 and water

  SO3 + H2O —> H2SO4

  pH =1
• Al2O3 with sulfuric acid

  Al2O3 + 3H2SO4 —> Al2(SO4)3 + 3H2O