The oxidation number of oxygen in ozone, O3 is +3 -3 +2 -2 0
The correct answer and explanation is:
Correct Answer: –2
Explanation (300 words):
The oxidation number (or oxidation state) of an element in a compound or molecule represents the effective charge that atom would have if all bonds were ionic. In most compounds, oxygen typically has an oxidation number of –2, and this remains true in ozone (O₃).
Let’s break it down:
1. Structure of Ozone (O₃):
Ozone is a triatomic molecule composed entirely of oxygen atoms. It has a bent structure and is a resonance hybrid of two structures, where a double bond and single bond alternate between the three atoms. Despite the differing bond types in resonance structures, the oxidation number is assigned based on rules, not bond type.
2. Rule for elements in their elemental form:
Ozone is made up only of oxygen atoms. Like O₂ (dioxygen), it is an elemental form of oxygen, not a compound with other elements.
Important Rule:
For an element in its elemental form (like O₂, O₃, H₂, N₂, etc.), the oxidation number is always 0.
This rule applies regardless of how many atoms are bonded together, as long as they are atoms of the same element.
So, although oxygen typically has an oxidation number of –2 in compounds like H₂O or CO₂, in ozone, which is a pure element, the oxidation number of each oxygen atom is 0.
Answer Recap:
- Ozone is a molecule made only of oxygen atoms.
- Since it’s in elemental form, each atom’s oxidation number is 0.
- Therefore, the correct oxidation number of oxygen in O₃ is 0.