Dichromate Ion overview
The stored Lewis connectivity is [O₃Cr—O—CrO₃]²⁻. A bridging oxygen connects two chromium centers; representative Lewis contributors distribute Cr=O and Cr–O⁻ bonds across terminal oxygens.
How to draw Cr₂O₇²⁻
- Count 56 valence electrons. Include charge adjustments before drawing.
- Use the reviewed connectivity [O₃Cr—O—CrO₃]²⁻. Do not infer a different isomer from the formula alone.
- Place the required single, double or multiple bonds. Keep a running electron total.
- Complete terminal valence shells and add lone pairs or formal charges. A bridging oxygen connects two chromium centers; representative Lewis contributors distribute Cr=O and Cr–O⁻ bonds across terminal oxygens.
- Verify the total electron count and geometry. The reviewed geometry is Two tetrahedral CrO₄ units sharing one oxygen.
Why this example matters
A bridging oxygen connects two chromium centers; representative Lewis contributors distribute Cr=O and Cr–O⁻ bonds across terminal oxygens.
Scope and model limits
This is a transition-metal electron-bookkeeping model, not a complete metal–oxygen molecular-orbital description.
Common mistakes
- Drawing two disconnected chromate ions
- Omitting the bridging oxygen
- Applying a simple main-group octet rule to chromium
Related reviewed guides
Last reviewed: 2026-07-16. Educational reference only; verify graded work with course materials.