Period 3 elements

• Why is sodium more reactive than Magnesium?

  As Mg2+ requires more energy to remove an electron.
• What happens when sodium is added to cold water?

  Reacts vigorously forming a ball and fizzing.

  Produces H2 gas and alkaline solution of NaOH.

  2Na(s) + H2O(l) > 2NaOH(aq) + H2(g)
• What happens when magnesium is added to cold water?

  Reacts slowly forming a weak alkaline solution of Mg(OH)2. This is sparingly soluble, so little OH- ions in solution.

  Mg(s) + H2O(l) > Mg(OH)2(aq) + H2(g)
• What happens when Magnesium reacts with steam?

  Reacts quicker with steam producing white solid, white light.

  Mg(s) + H2O(g) > MgO(s) + H2(g)
• What element doesn't make a solid when reacting with oxygen?

  Sulfur forms SO2(g). With higher temps and a catalyst it forms SO3.

  S(s) + O2(g) > SO2(g)
• Reactions with oxygen?

  2Na(s) + 1/2O2(g) > Na2O(s)

  Mg(s) + O2(g) > MgO(s)

  2Al(s) + 1.5O2(g) > Al2O3(s)

  P4(s) + 5O2(g) > P4O10(s)

  Si(s) + O2(g) > SiO2(s)
• Formation of oxide?

  Na2O= Very fast

  MgO= Very fast

  Al2O3= Slow (fast if powdered)

  SiO2= Slow

  P4O10= Spontaneous combustion

  SO2= Steadily burns
• Na2O, MgO, Al2O3 structure/bonding?

  Giant ionic lattices. Lots of strong attractive forces that require lots of energy to break.
• Why is MgO mp higher than Na2O?

  2+ ions are more strongly attracted to the oxygen, so require more energy to overcome.
• Why does Al2O3 have a lower mp than MgO?

  As Al3+ ions distort the electron cloud of oxygen causing some covalent character as well as ionic. This means less energy is required to break bonds.
• SiO2 mp?

  Higher than other non metals as it forms a macromolecular structure with many strong covalent bonds to break.
• P4O10 and SO2 mp?


  Low mp as simple molecular structures have weak intermolecular forces, so less energy required to break the bonds.
• Ionic oxides?

  Na and Mg form alkaline solutions when added to water.

  They contain O2- ion which accepts protons from the water molecule when dissolved in solution.
• Sodium and water?

  Na2O(s) + H2O(l) > 2NaOH(aq)

  Dissolves readily to form alkaline solution of pH 12-14.
• Magnesium and water?

  MgO(s) + H2O(l) > Mg(OH)2(aq)

  Dissolves sparingly so solution isn't as strong with pH of 9-10
• Simple covalent oxides?

  P and S form acidic solutions when added to water with pH of 0-2.

  The acid formed dissociates in solution forming H+ ions and negative ions.
• Phosphorus oxide + water?

  P4O10(s) + 6H2O(l) > 4H3PO4(aq)

  Dissolves: H3PO4(aq) > 3H+(aq) + PO43-(aq)
• Sulfur dioxide + water

  SO2(g) + H2O(l) > H2SO3(aq)

  Dissolves: H2SO3(aq) > 2H+(aq) + SO32-(aq)
• Sulfur trioxide + water?

  SO3(l) + H2O(l) > H2SO4(aq)

  Dissolves: H2SO4(aq) > 2H+(aq) + SO42-(aq)
• Silicon dioxide + water?

  Forms giant covalent structure with many strong covalent bonds, requiring lots of energy to break.

  Insoluble in water.

  It reacts with a base to form a salt, so classed as an acid.
• Aluminium oxide + water?

  Is amphoteric.

  Has both covalent and ionic character and is insoluble in water.

  Reacts with both acids and bases to form salts.
• Acid- base reactions?

  acid + base > salt + water
• Reactions involving basic oxides?

  2HCl(aq) + MgO(s) > MgCl2(aq) + H2O(l)

  H2SO4(aq) + Na2O(s) > Na2SO4(aq) + H2O(l)
• Reactions involving acidic oxides?

  2NaOH(aq) + SiO2(s) > Na2SiO3(aq) + H2O(l)

  12NaOH(aq) + P4O10(s) > 4Na3PO4(aq) + 6H2O(l)

  2NaOH(aq) + SO2(g) > Na2SO3(aq) + H2O(l)

  2NaOH(aq) + SO3(g) > Na2SO4(aq) + H2O(l)
• Reactions involving amphoteric oxides?

  2NaOH(aq) + Al2O3(s) + 3H2O(l) > 2NaAl(OH)4(aq)

  3H2SO4(aq) + Al2O3(s) > Al2(SO4)3(aq) + 3H2O(l)
• Sodium properties?

  Metallic, shiny, conducts electricity.
• Reaction of sodium with an acid?

  Na + acid > H2 + salt
• Reaction of sodium with water?

  Vigorous reaction, floats on water, fizzes

  2Na + H2O > 2NaOH + H2
• Sodium and oxygen reaction?

  Yellow flame, forms white powder of Na2O

  2Na + 1/2O2 > Na2O
• Reaction of Mg with water?

  Slow reaction as Mg(OH)2 is sparingly soluble

  Mg + 2H2O > Mg(OH)2 + H2
• Reaction of Mg with steam?

  Much faster.

  Mg + H2O > MgO + H2
• Reaction of Mg with oxygen?

  White flame, white powder of MgO.

  2Mg + O2 > 2MgO
• Reaction of Al with water?

  No reaction
• Reaction of Al with oxygen?

  Bright flame, white powder

  4Ag + 3O2 > 2Al2O3
• Reaction of silicon with oxygen?

  Si + O2 > SiO2
• Properties of phosphorus?

  Non-metal, low mp, low bp, non-conductor
• Reaction of phosphorus and excess oxygen?

  4P + 5O2 > P4O10
• Reaction of phosphorus and limited oxygen?

  4P + 3O2 > P4O6
• Sulfur and oxygen reaction?

  S + O2 > SO2
• Highest oxide period 3 compound?

  MgO as stronger ionic bonding than Na2O. Al2O3 is lower due to covalent character of bonding.