Period 3 elements are Na, Mg, Al, Si, P, S, Cl to Ar

• Atomic number ranges from 11 to 18

• Have 3 electron shells

• The metals change from metals Na, Mg, Al to metalloids (Si) to non-metals that are P, S, Cl, Ar.

Structure of Period 3 elements

• The structure of the elements also change across

• P, S, Cl and Ar form simple molecules

• Si forms a giant covalent structure

• Na, Mg and Ai form metallic structures

Metallic Structure: Strong attraction is present.

Giant covalent structure: Strong covalent bonds between atoms.

Simple molecules: Weak Van der Waals forces between molecules.

Melting and boiling point

• Na, Mg and I have high melting and boiling point [strong metallic bonding]

• Si has high melting and boiling point due to strong covalent bond

• P, S and Cl are simple molecules [Van der Waals]. Have the lowest melting and boiling point

Electrical conductivity

• Na, Mg and AI conduct electricity because of delocalized electron and electron are move freely

• Si is a semiconductor and conduct at high temperature. No free electron at room temperature

• P, Cl, CL and Ar do not conduct electricity [simple molecules]

• Cl has a negative oxidation number which is -1

• The oxidation state is the same as the number of electrons in the valence shell of the period 3 element.

  Bonding and structure:

  Bonding :

• NaCl and MgCl2 (strong ionic bonding between cations and anions)

• AlCl3, SiCl4, PCl5 (Weak intermolecular forces of attraction between molecules)

  Structure :

• NaCl and MgCl2 (Giant ionic lattice)

• AlCl3, SiCl4, PCl5 (Simple molecular)

Reactions :

Reaction with water

• NaCl does not react with water, it dissolves in water to give a neutral solution

• MgCl2 reacts with water to give a faintly acidic solution (The Mg2+ pulls electrons from the O in H2O molecules towards it which makes the H in H2O slightly positive to be pulled off by H2O, forming H3O+ which is acidic.

• Solid AlCl3 reacts violently with water, producing steamy fumes of hydrogen chloride gas. An acidic solution is formed when solid AlCl3 is added into excess of water.

• AlCl3 reacts with water to give an acidic solution, and Hexaaquaaluminium ions are formed. The 3+ charge on the Al pulls electrons from the O in H2O molecules strongly towards it. This makes the H in H2O more positive and easier to remove, amking it more acidic.

• SiCl4 reacts with water violently, producing silicon dioxide and fumes of hydrogen chloride. In large excess of water, the hydrogen chloride will dissolve to give a strongly acidic solution containing hydrochloric acid.

• PCl5 reacts violently with water, producing fumes of hydrogen chloride. If there is enough water present, these will dissolve to give a solution containing HCl.

  • With cold water, phosphorus oxychloride, POCl₃, is produced along with HCl.

  • With boiling water, phosphorus (V) chloride reacts to give phosphoric (V) acid and more HCl.

• Reaction with acid

  • forming salt

  NaOH _(aq) + HCl _(aq) --> NaCl _(aq) + H₂O _(l)

Magnesium hydroxide (Mg(OH2))

• Reaction with acid

  • forming salt

  Mg(OH)_{2 (s)} + 2HCl _(aq) --> MgCl_{2 (aq)} + 2H₂O _(l)

Aluminium hydroxide (AI(OH3)) - amphoteric

• Reaction with hydrochloric acid

  • forming aluminium chloride

  Al(OH)_{3 (s)} + 3HCl _(aq) --> AlCl_{3 (aq)} + 3H₂O _(l)

  
  

• Reaction with sodium hydroxide

  • Forming sodium tetrahydroxoaluminate (colouless solution)

  Al(OH)_{3 (s)} + NaOH _(aq) --> NaAl(OH)_{4 (aq)}

• Bonding

  • Na2O, MgO and Al2O3 (metals) have ionic bonds in their ionic lattice

  • SiO2 (metalloid) has covalent bonds their giant covalent structure

  • P4O10 and SO3 (non-metals) have covalent bonding and weak intermolecular forces (Van Der Waal’s forces of attraction)

• Structure

  • From metals (Na2O, MgO and Al2O3) to metalloids (SiO2) to non-metals (P4O10 and SO3), the structures change from giant ionic lattices to giant covalent structure to simple molecular structures

Reactions:

1. Reactions of Na₂O:

   1. Sodium oxide reacts with cold water to form sodium hydroxide

      1. Na₂O(s) + H₂O (l)--> 2NaOH (aq)

   2. Sodium oxide reacts with hydrochloric acid to produce sodium chloride

      1. Na₂O _(s) + 2HCl _(aq) --> 2NaCl _(aq) + H₂O _(l)

2. Reactions of MgO:

   1. Magnesium oxide reacts with water to form magnesium hydroxide.

      1. MgO _(s) + H₂O _(l) --> Mg(OH)_{2 (s)}

   2. Magnesium oxide reacts with warm HCl to produce magnesium chloride

      1. MgO _(s) + 2HCl _(aq) --> MgCl_{2 (aq)} + H₂O _(l)

3. Reactions of Al₂O₃:

   1. Aluminum oxide is unreactive with water

   2. Aluminum oxide reacts with warm HCl to produce aluminum chloride

      1. Al₂O_{3 (s)} + 6HCl _(aq) --> 2AlCl_{3 (aq)} + 3H₂O _(l)

   3. Aluminum oxide reacts with sodium hydroxide to produce sodium tetrahydroaluminate

      1. Al₂O_{3 (s)} + 2NaOH _(aq) + 3H₂O _(l) --> 2NaAl(OH)_{4 (aq)}

4. Reactions of SiO₂:

   1. Silicon dioxide does not react with water

   2. Silicon dioxide reacts with sodium hydroxide to form sodium silicate.

      1. SiO_{2 (s)} + 2NaOH _(aq) --> Na₂SiO_{3 (aq)} + H₂O _(l)

5. Reactions of P₄O₁₀:

   1. Phosphorus (V) oxide reacts with water to form phosphoric (V) acid.

      1. P₄O_{10 (s)} + 6H₂O _(l) --> 4H₃PO_{4 (aq)}

   2. Phosphorus (V) oxide reacts with sodium hydroxide solution to form sodium phosphate salt.

      1. P₄O_{10 (s)} + 12NaOH _(aq) --> 4Na₃PO_{4 (aq)} + 6H₂O _(l)

6. Reactions of SO₃:

   1. Sulphur trioxide reacts violently with water to produce a fog of sulphuric (VI) acid droplets.

      1. SO_{3 (g)} + H₂O _(l) --> H₂SO_{4 (aq)}

   2. Sulphur trioxide reacts with sodium hydroxide solution to form sodium sulphate salt.

      1. SO_{3 (g)} + 2NaOH _(aq) ® Na₂SO_{4 (aq)} + H₂O _(l)