Lewis Structure Generator
Reviewed oxyacid guide

H₃PO₄ Lewis Structure: Phosphoric Acid

A common classroom structure is O=P(OH)₃. Three oxygens carry hydrogen, and the fourth oxygen is commonly drawn double bonded to phosphorus.

Reviewed July 16, 2026 · Classroom Lewis convention

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Quick answer

Valence electrons

3 H contribute 3, P contributes 5 and 4 O contribute 24: 32 electrons.

Connectivity

Three O atoms are –OH groups; one oxygen is shown as P=O.

Geometry

Four P–O domains produce tetrahedral geometry around phosphorus.

Drawing steps

  1. Place phosphorus in the center with four oxygen atoms.
  2. Attach each of the three hydrogens to a separate oxygen.
  3. Complete terminal oxygen octets while maintaining 32 electrons.
  4. Draw the remaining non-hydroxyl oxygen as P=O in the common minimized-charge form.
  5. Verify that the displayed formal charges are zero.

Functional meaning

The three P–OH groups explain why phosphoric acid is triprotic: the molecule can lose three protons in successive acid–base steps, producing H₂PO₄⁻, HPO₄²⁻ and PO₄³⁻.

Common mistake: placing hydrogen directly on phosphorus. In this oxyacid, all three acidic hydrogens are attached to oxygen.