Ozone cannot be represented completely by one fixed bond pattern. Its two equivalent resonance contributors each contain one O–O single bond, one O=O double bond and opposite formal charges.
Two equivalent contributors; actual O–O bonds are equivalent
Total valence electrons18
Central atomOxygen
Molecular geometryBent
Bond angle≈117°
O3 Lewis structure overview
Three oxygen atoms contribute eighteen valence electrons. A chain skeleton uses two bonds. After completing octets, one terminal lone pair must become a double bond so the central oxygen reaches an octet. Either terminal oxygen can form that double bond, producing two equivalent resonance contributors.
How to draw the O3 Lewis structure
Count 18 valence electrons.
Each oxygen contributes six.
Draw an O–O–O skeleton.
Two single bonds use four electrons.
Complete terminal octets.
Place three lone pairs on each terminal oxygen, then place the remaining pair on the central oxygen.
Create one double bond.
Move a lone pair from either terminal atom into a bond so the central oxygen has an octet.
Draw both resonance forms.
Swap the single and double bonds and show the associated formal charges.
Formal charges and resonance
In each contributor, the central oxygen has formal charge +1, the singly bonded terminal oxygen has -1, and the double-bonded terminal oxygen is neutral. The real molecule is a resonance hybrid, so its two O–O bonds have the same intermediate bond order.
Geometry and polarity
The central oxygen has three electron domains: two bonding regions and one lone pair. That gives trigonal-planar electron geometry and bent molecular geometry. Because the shape is bent, O3 has a net dipole.
Common mistakes
Drawing two ordinary single bonds without giving the central oxygen an octet.
Drawing two O=O double bonds, which uses too many electrons for second-period oxygen.
Showing only one contributor and treating its single and double bonds as permanently different.
Leaving formal charges off the charge-separated resonance structures.
Frequently asked questions
Are the two O–O bonds in ozone different?
No. The resonance hybrid makes the two measured bonds equivalent, with bond order between a single and double bond.
How many lone pairs are on the central oxygen?
The central oxygen has one lone pair in each major resonance contributor.
Is ozone linear?
No. A lone pair on the central oxygen gives ozone a bent shape.