Period 3

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Created by
Sophie Gaved

Cards (34)

  • The melting points of the period 3 elements are linked to the bond strength and structure.
  • Sodium, magnesium and aluminium (groups 1, 2, 3) are all metals with metallic bonding. The melting point across them increases due to greater positive charged ions and thus greater electrostatic forces of attraction between ions and delocalised electrons.
  • Silicon (group 4) has a macromolecular structure with strong covalent bonds between all molecules. Covalent bonds require a lot of energy to break and so silicon has a very high melting point.
  • Phosphorus, sulfur and chlorine (groups 5, 6, 7) are all simple covalent molecules held together with weak van der waals forces which don't require much energy to overcome. Van der waals increase with size however, and since these elements are naturally found as P4, S8 and Cl2, this determines the order of their melting points.
  • In water, sodium floats and moves, fizzes and may catch fire with a yellow - orange flame. The equation is 2 Na + 2 H2O -> 2 NaOH + H2.
  • In water magnesium has a very slow reaction with equation Mg + 2 H2O -> Mg(OH)2 + H2.
  • In steam magnesium burns with a white flame forming a white powder. The equation is Mg + H2O -> MgO + H2.
  • In water chlorine dissolves giving a very pale green solution with equation Cl2 + H2O <-> HCl + HOCl.
  • In oxygen, sodium burns with a yellow - orange flame to produce a white powder. The equation is 4 Na + O2 -> 2 Na2O.
  • In oxygen, magnesium burns with a white flame to produce a white powder. The equation 2 Mg + O2 -> 2 MgO.
  • In oxygen, aluminium burns with a white flame to produce a white powder. The equation is 4 Al + 3 O2 -> 2 Al2O3.
  • In oxygen, silicon burns with a white flame to produce a white powder. The equation is Si + O2 -> SiO2.
  • In oxygen phosphorus burns with a very bright white flame to produce white powder. The equation is P4 + 5 O2 -> P4O10.
  • In oxygen, sulfur burns with a blue flame and gives off a choking gas. The equation is S + O2 -> SO2.
  • Sodium forms an oxide of Na2O which is solid and has an ionic structure.
  • Magnesium forms an oxide of MgO which is solid and has an ionic structure.
  • Aluminium forms an oxide of Al2O3 which is solid and has an ionic structure with some covalent character due to the polarising nature of Al 3+ ions.
  • Silicon forms an oxide of SiO2 which is solid and has a giant covalent structure.
  • Phosphorus forms an oxide of P4O10 which is solid and has simple molecular structure.
  • Sulfur forms an oxide of either SO2 or SO3 which are gas and liquid respectfully and both have simple molecular structure.
  • Na2O dissolves in water and then the O 2- ions react with water to form a solution of pH 14 with equation Na2O + H2O -> 2 NaOH.
  • MgO slightly dissolves and the O 2- ions react with water to form a solution of pH 10 with equation MgO + H2O -> Mg(OH)2.
  • Al2O3 is insoluble in water due to a high lattice enthalpy.
  • SiO2 is insoluble in water due to giant covalent structure.
  • P4O10 reacts violently in water as water attaches to the partially positive P atoms, releasing H + ions, with pH 0. The equation is P4O10 + 6 H2O -> 4 H3PO4.
  • SO2 dissolves and then reacts with water to form a solution as water attaches to the partially positive S atoms, releasing H + ions, with pH 3. The equation is SO2 + H2O -> H2SO3.
  • SO3 reacts violently with water as water attaches to the partially positive S atoms, releasing H + ions, with pH 0. The equation is SO3 + H2O -> H2SO4.
  • Na2O is basic and reacts with acids with the equation Na2O + 2 H + -> 2 Na + + H2O.
  • MgO is basic and reacts with acids with the equation MgO + 2 H + -> Mg 2+ + H2O.
  • Al2O3 is amphoteric and reacts with acids with the equation Al2O3 + 6 H + -> 2 Al 3+ + 3 H2O and with bases with the equation Al2O3 + 2 OH - + 3 H2O -> 2 Al(OH)4 -.
  • SiO2 is acidic and reacts with bases (specifically hot, concentrated NaOH) with the equation SiO2 + 2 OH - -> SiO3 2- + H2O.
  • P4O10 is acidic and reacts with bases with the equation P4O10 + 12 OH - -> 4 PO4 3- + 6 H2O.
  • SO2 is acidic and reacts with bases with the equation SO2 + 2 OH - -> SO3 2- + H2O.
  • SO3 is acidic and reacts with bases with the equation SO3 + 2 OH - -> SO4 2- + H2O.