Why shape matters
Bent geometry leaves a net molecular dipole.
The two polar S–O contributions do not cancel.
Molecular compound · sulfur oxide
Sulfur dioxide
SO₂
Sulfur dioxide is SO₂, a bent molecular oxide. Its geometry prevents the two S–O bond dipoles from canceling, so SO₂ has a permanent molecular dipole.
Environmental context: atmospheric SO₂ participates in further oxidation and acidification chemistry.
Essentials
The first fact to see is that SO₂ is bent, not linear.
The beginner view needs shape before numerical detail.
Detail
The gas-phase O–S–O angle is about 119.5°.
NIST experimental geometry gives a value close to 119.5°. The displayed value is rounded.
Resonance
No single Lewis contributor permanently assigns one special S–O bond.
Electron density is delocalized across the S–O framework.
Understand
SO₂ can be oxidized further to SO₃.
The balanced equation connects the two sulfur oxides; real pathways depend on catalysts or radical chemistry.
In water
Dissolved SO₂ participates in bisulfite/sulfite equilibria.
A single pure H₂SO₃ molecule picture is an oversimplification of the aqueous system.
Reference identifiers
Names and identifiers that pin down the chemical identity.
| Formula | SO₂ |
|---|---|
| CAS Registry Number | 7446-09-5 |
| PubChem CID | 1119 |
Advanced
Push past the first model without losing the simple picture.
Why bent while CO₂ is linear?
Their valence-electron structures and central-atom electron domains differ.
Is the angle exactly 120°?
No. Experimental gas-phase SO₂ is about 119.5°.
Does SO₂ in water simply become H₂SO₃ molecules?
Aqueous sulfur(IV) chemistry is better described with dissolved SO₂ plus acid–base equilibria.
Constituent elements