Periodicity

• Highest mp in period 3?


  Silicon as it is macromolecular and has strong covalent bonds that require lots of energy to overcome.
• Highest ionisation energy in period 3?


  Argon as it contains the most protons with the same amount of shielding.
• Why does the atomic radius decrease along period 3?


  As the no. of protons increases so the attraction between nucleus and electrons is greater.
• Why is sulfurs mp higher than phosphorus?


  As S8 molecules are bigger than P4 molecules, therefore VDW forces are stronger in sulfur.
• Why does sodium oxide form an alkaline solution when reacting with water?


  As sodium oxide contains O2- ions which react with water to form OH- ions.
• Phosphorus oxide symbol?


  P4O10
• Why does nickel have a high mp?


  As it has strong metallic bonding between the positive ion core and delocalised sea of electrons.
• Why is nickel ductile?


  Layers of atoms/ions can slide over eachother
• Will Sr or Rb have a bigger atomic radius?


  Rb as it contains less protons with similar shielding.
• State the trend in ionisation energies along period 3?


  Increases as no. protons increases with same amount of shielding.
• Why is sulfurs mp greater than phosphorus?


  Both are simple molecular structures but S8 is a bigger molecule compared to P4, so stronger VDW forces to overcome.
• Why is the mp of Al greater than Na?


  As Al contains more protons and delocalised electrons, so stronger metallic bonding.
• Equation and observance when Mg is heated with steam?


  Mg(s) + H2O(g) > MgO(s) + H2(g)

  White solid, white light.
• Equation and observance when Na is heated with O2?


  4Na + O2 > 2Na2O

  Yellow solid, yellow flame
• Why does sodium oxide have a high mp?


  As ionic lattice contains strong attraction between oppositely charged Na+ and O2- ions.
• Why does sulfur oxide have a lower mp than phosphorus oxide?


  As SO2 is a smaller molecule than P4O10 so weaker VDW forces between molecules require less energy to overcome.
• Why is silicon oxide classified as an acidic oxide?


  As it reacts with alkalis.

  eg SiO2 + 2NaOH >Na2SiO3 + H2O
• Why is the mp of S8 greater than P4?


  S8 molecules are bigger therefore contain stronger VDW forces.
• Why does Na2O form an alkaline solution when reacting with H2O?


  As it contains O2- atoms, which react with water forming OH- ions.
• Phosphorus oxide reacting with excess sodium hydroxide solution?


  P4O10 + 12OH- > 4PO43- + 6H2O
• Why is Mg mp greater than Na?


  Mg2+ attracts delocalised electrons more strongly as greater charge.
• Silicon dioxide SiO2


  Macromolecular structure with covalent bonding.

  Physical properties: Brittle, hard, insoluble, non conductor.
• Phosphorus oxide P4O10


  Simple molecular structure with covalent bonding.

  VDW forces between molecules.
• sulfur oxide reacting with water?


  SO2 + H2O > HSO3-+ H+

  Why does it form a weak acidic solution= Only partially ionised.
• Phosphorus oxide reacting with magnesium oxide?


  P4H10+ 3MgO > 3Mg(PO4)2
• Bonding in MgO?


  Ionic.

  Experiment to prove ionic bonding= Melt MgO. The molten oxide conducts electricity.
• Why is silicon dioxide insoluble in water?


  As it is macromolecular and contains strong covalent bonds that water can't break.
• Is p4O10 mp lower than SiO2?


  Yes as it is a simple molecular with covalent bonds. The VDW forces are weak between molecules.
• Phosphorus oxide reacting with sodium hydroxide?


  P4O10 + 12NaOH > 4Na3PO4 + 6H2O
• Why does sodium oxide have a high mp?


  Na2O is an ionic lattice with strong forces of attraction between ions
• Why does SO3 have a higher mp than SO2?


  As SO3 is a larger molecule so VDW forces are stronger.
• How do some Period 3 oxides have basic properties?


  Ionic bonding contains O2- ions which accept protons to form OH-.
• Why is SiO2 an acidic oxide if it doesn't dissolve in water?


  As it reacts with bases.
• Why is white phosphorus P4 stored underwater?


  To prevent it from reacting with oxygen.
• Why does P4O10 have a higher mp than SO2?


  As it is a bigger molecule so contains stronger VDW forces
• Phosphoric oxide reacting with water?


  P4O10 + 6H2O > 4H3PO4

  pH= 1
• Phosphoric acid reacting with magnesium oxide? 


  2H3PO4 + 3MgO > Mg3(PO4)2
• Why is excess MgO used for neutralisation?


  As it is insoluble
• Why does sodium oxide have a high mp?


  As ionic lattice has strong attraction between oppositely charged ions.
• Why does sulfur dioxide have a low mp?


  As molecular structure has weak VDW forces between molecules.