Lewis Structure Generator
Chlorate ion · ClO3−

ClO3− Lewis Structure

A common minimized-formal-charge contributor has two Cl=O bonds, one Cl–O⁻ bond and one lone pair on chlorine. Moving the single-bonded oxygen produces three equivalent resonance contributors.

Open ClO3− in the generatorSee drawing steps
ClO₃⁻
[ O=Cl(=O)—O⁻ ]
One representative expanded-octet contributor
Total valence electrons26
Resonance forms3 equivalent
Central lone pairs1
GeometryTrigonal pyramidal

ClO3− overview

Seven electrons come from chlorine, eighteen from three oxygens and one from the charge. After three Cl–O bonds and terminal octets are placed, one lone pair remains on chlorine. An expanded-octet representation reduces formal-charge separation.

How to draw ClO3−

  1. Count 26 valence electrons.
  2. Place chlorine in the center with three oxygen atoms.
  3. Complete oxygen octets and place the remaining lone pair on chlorine.
  4. Convert two oxygen lone pairs into Cl=O bonds.
    This gives two double bonds and one single-bonded O− in the common expanded-octet model.
  5. Draw all three resonance contributors.

Formal charges and conventions

In the displayed contributor, chlorine and the two double-bonded oxygens have formal charge zero; the single-bonded oxygen is −1. Some courses prefer an all-single-bond charge-separated structure. Follow your course convention.

Why is the shape pyramidal?

Chlorine has four electron domains: three bonding regions and one lone pair. The electron-domain arrangement is tetrahedral, while the molecular geometry is trigonal pyramidal.

Common mistakes

  • Counting only 25 electrons and forgetting the charge.
  • Leaving chlorine without its lone pair.
  • Showing only one resonance contributor.
  • Calling the molecule trigonal planar.

Last reviewed: July 16, 2026. Educational reference only.