CIE AS Chemistry (9701) exams from 2022

Revision Notes

2.1.3 Period 3 Oxides

Period 3: Oxides

Reactions with oxygen & chlorine

Reaction of Period 3 elements with oxygen table

The Periodic Table - Table 1_Period 3 Oxides, downloadable AS & A Level Chemistry revision notes

The Periodic Table - Period 3 Oxygen Reactions (1), downloadable AS & A Level Chemistry revision notes The Periodic Table - Period 3 Oxygen Reactions (2), downloadable AS & A Level Chemistry revision notes The Periodic Table - Period 3 Oxygen Reactions (3), downloadable AS & A Level Chemistry revision notes The Periodic Table - Period 3 Oxygen Reactions (4), downloadable AS & A Level Chemistry revision notes

The diagrams above show the reactions of the Period 3 elements with oxygen

Reaction of Period 3 elements with chlorine table

The Periodic Table - Table 2_Period 3 Oxides, downloadable AS & A Level Chemistry revision notes

Reaction of sodium & magnesium with water

  • Sodium reacts vigorously with cold water:

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

  • The sodium melts into a ball and moves across the water surface until it disappears
  • Hydrogen gas is given off
  • The solution formed is strongly alkaline (pH 14) due to the sodium hydroxide which is formed

The Periodic Table - Sodium Reaction with Water, downloadable AS & A Level Chemistry revision notes

The diagram shows the reaction of sodium with cold water

  • Magnesium reacts extremely slowly with cold water:

Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g)

  • The solution formed is weakly alkaline (pH 11) as the formed magnesium hydroxide is only slightly soluble
  • When magnesium is heated, it reacts vigorously with steam (water) to make magnesium oxide and hydrogen gas:

Mg(s) + H2O(g) → MgO(s) + H2(g)

Oxidation Number of the Period 3 Oxides

  • Oxygen is more electronegative than any of the Period 3 elements

 

Hydrocarbons Pauling Scale of Elements, downloadable AS & A Level Chemistry revision notes

The Pauling scale shows the electronegativities of the elements in the periodic table. Oxygen has a higher electronegativity than any of the Period 3 elements which is why the Period 3 elements will have positive oxidation states and the oxygen a negative oxidation state in the oxides of Period 3 elements

  • The Period 3 elements therefore have positive oxidation states in their oxides and the oxygen has a negative oxidation state of -2

 

The Periodic Table - Oxidation States Period 3 Oxides (1), downloadable AS & A Level Chemistry revision notes

The Periodic Table - Oxidation States Period 3 Oxides (2), downloadable AS & A Level Chemistry revision notes

Oxidation states of the Period 3 elements in their oxides

Formulae of the oxides of the Period 3 elements & their oxidation states table

The Periodic Table - Table 1_Oxidation Number of the Period 3 Oxides, downloadable AS & A Level Chemistry revision notes

Reaction of Period 3 Oxides & Water

  • Not all Period 3 oxides react with or are soluble in water

Reaction of Period 3 oxides with water table

The Periodic Table - Table 1_Reaction of Period 3 Oxides & Water, downloadable AS & A Level Chemistry revision notes

Exam Tip

Since aluminium oxide does not react or dissolve in water, the oxide layer protects the aluminium metal from corrosion.

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