SO4²− structure overview
Sulfur contributes 6 electrons, four oxygens contribute 24, and the −2 charge adds 2: 6 + 24 + 2 = 32. Four S–O connections create four electron domains around sulfur.
How to draw sulfate
- Count 32 electrons.Remember the two additional electrons from the charge.
- Draw four S–O single bonds.Place sulfur in the center.
- Complete oxygen octets.The octet-only structure places formal charge +2 on sulfur and −1 on each oxygen.
- Apply the convention required by your course.A common expanded-octet form converts two oxygen lone pairs into S=O bonds, reducing formal-charge separation.
- Show resonance and brackets.The positions of the two double bonds can be selected in six ways; the complete ion is enclosed in brackets with 2−.
Why sulfate drawings differ
Lewis structures are bookkeeping models. Some courses emphasize the octet-only contributor; others use expanded-valence S=O contributors. The real bonding is delocalized and should not be interpreted as two fixed short bonds and two fixed long bonds.
Geometry
Four sigma-bond domains around sulfur produce tetrahedral molecular geometry. Resonance changes electron placement, not the tetrahedral atom arrangement.
Common mistakes
- Using 30 electrons instead of 32.
- Forgetting the overall 2− bracket charge.
- Calling the molecule square planar because four oxygens are drawn in a cross.
- Presenting one contributor as the only possible electron placement.
Related guides
Reviewed July 16, 2026. Educational reference only; follow the bonding convention required by your course.