9.2.1—Reactions of the elements with oxygen (to
- Syllabus
- 9701–2028–2029
- Objective
- 9.2.1
- Level
- AS
Period 3 elements react with oxygen according to their bonding and oxide type
Period 3 elements form oxides with different structures and acid–base behaviour. Metallic oxides are generally ionic/basic, while non-metal oxides are molecular/covalent and more acidic.
Use oxidation states and the balanced equation to compare products. The change from ionic to covalent bonding across the period explains the shift in oxide behaviour.
Na₂O reacts with water to form NaOH, whereas SO₂ dissolves to form an acidic solution. Silicon dioxide is a giant covalent oxide and does not behave like a simple molecular oxide.
Do not label every oxide simply “basic” or “acidic” without considering structure and whether it reacts with water. Amphoteric cases need their own evidence.
ConceptA-Level CAIE Chemistry AS