Ozone (O3) — Structure

SMILES: [O-][O+]=O

Molecular parameters:

• Hybridization: sp2 (central O)
• Geometry: Angular (V-shaped/bent)
• Bond angle: ~117° (slightly less than 120° due to lone pair compression)
• Bond order: 1.5 (resonance hybrid of two structures)
• Nature: Resonance hybrid — no single bond/double bond distinction

Resonance structures:

$\overset{+}{\text{O}} = \overset{-}{\text{O}} - \text{O} \longleftrightarrow \text{O} - \overset{+}{\text{O}} = \overset{-}{\text{O}}$

Preparation: $3\text{O}_2 \xrightarrow{\text{silent electric discharge}} 2\text{O}_3$

Detection reaction (KI-starch paper test): $\text{O}_3 + 2\text{KI} + \text{H}_2\text{O} \rightarrow 2\text{KOH} + \text{O}_2 + \text{I}_2$

I2 + starch → blue-black complex (positive test for ozone)

Oxidizing action (nascent oxygen mechanism): $\text{O}_3 \rightarrow \text{O}_2 + [\text{O}] \text{ (nascent/atomic oxygen)}$

Nascent oxygen is extremely reactive — more reactive than O2.

Ozone layer protection: $\text{O}_3 \xrightarrow{\text{UV 200-300 nm}} \text{O}_2 + [\text{O}] \quad \text{(absorbs harmful UV-B and UV-C)}$