Lewis Structure Generator
Phosphate ion · PO4 3−

PO4 3− Lewis Structure

A common minimized-formal-charge contributor has one P=O bond and three P–O⁻ bonds. The double bond can be placed on any oxygen, producing four equivalent resonance contributors.

Open PO4 3− in the generatorSee drawing steps
PO₄³⁻
[ O=P(—O⁻)₃ ]³⁻
Representative expanded-octet contributor
Total valence electrons32
Resonance forms4 equivalent
Overall charge−3
GeometryTetrahedral

PO4 3− overview

Phosphorus contributes five electrons, four oxygens contribute twenty-four and the −3 charge adds three. Four P–O bonds create a tetrahedral skeleton. Lewis courses commonly use either an all-single-bond charge-separated form or an expanded-octet contributor with one P=O bond.

How to draw PO4 3−

  1. Count 32 valence electrons.
  2. Put phosphorus in the center and attach four oxygens.
  3. Complete all oxygen octets.
  4. Choose the convention required by your course.
    The displayed minimized-charge form uses one P=O bond and three P–O⁻ bonds.
  5. Draw four equivalent resonance contributors and add the 3− charge.

Formal-charge conventions

In the displayed contributor, phosphorus and the double-bonded oxygen are zero, while three single-bonded oxygens are −1 each. The all-single-bond form gives phosphorus +1 and four oxygens −1.

Geometry

Four P–O bonding domains surround phosphorus. VSEPR therefore predicts tetrahedral geometry with idealized angles near 109.5°.

Common mistakes

  • Adding only one electron for a 3− charge.
  • Forgetting three negative formal charges in the displayed contributor.
  • Showing one contributor as the only possible Lewis form.
  • Drawing a square-planar arrangement.

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