Summary AQA A-Level Chemistry 2.4 Period Three Elements and Oxides

Periodicity
22.1 Reactions of Period 3 Elements
22.1 Reactions of period 3 elements
- The reactions of the elements in Period 3 are all redox
reactions 22.2 The oxides of elements in period 3
Reactions with Water: 22.3 The acidic/basic nature of the period 3 oxides
- Sodium
o Vigorous reaction, fizzes and floats on water. Forms a strongly alkaline solution.
o 2Na(s) + 2H2O(l) à2NaOH(aq) + H2(aq)
- Magnesium
o Slow reaction with water
o Mg(s) + H2O(l) à Mg(OH)2(aq) + H2(g)
o Much faster reaction with steam, burns with bright white flamed giving a white powder.
o Mg(s) + H2O(g) à MgO(s) + H2(g)
Reactions with Oxygen:
- Sodium
o Bright yellow flame to produce white powder
o 4Na(s) + O2(g) à 2Na2O(s)
- Magnesium
o Burns with a bright white flame to produce a white powder.
o 2Mg(g) + O2(g) à 2MgO(s)
- Aluminium
o Burns with white flame to produce white powder
o 4Al(s) + 3O2(g) à 2Al2O3(s)
- Silicon
o Si(s) + O2(g) à SiO2(s)
- Phosphorus
o White smoke (phosphorus pentoxide) given off
o 4P(s) + 5O2(g) à P4O10(s)
- Sulfur
o Burns with a blue flame to form a colourless gas (sulfur dioxide)
o S(s) + O2(g) à SO2(g)

22.2 The Oxides of Elements in Period 3
- Sodium and magnesium oxides are giant ionic lattices.
- Aluminium oxide is a giant ionic lattice with some covalent character, as the ion is very small with a
large positive charge so it can distort the O2- electron cloud.
- Silicon oxide has a giant covalent structure.
- Phosphorus and sulfur oxides are covalently bonded molecules
Na2O MgO Al2O3 SiO2 P4O10 SO3 SO2
Melting 1548 3125 2345 1883 573 290 200
point (K)
Bonding Ionic Ionic Ionic/ Covalent Covalent Covalent Covalent
covalent
Structure Giant ionic Giant ionic Giant ionic Giant Molecular Molecular Molecular
Covalent
- Phosphate ion
- Sulfate (VI) ion
- Sulfate (IV) ion