ION⁻

Forty-eight polyatomic ions, taken apart. Where the charge comes from, what shape it makes, what it is called, and what happens when you put it in a beaker.

How to trust this page

Every ion here carries an explicit electron budget. Before this page was built, an automated gate checked all forty-eight: that lone-pair electrons plus bonding electrons equal the valence electrons available, that formal charges sum to the ion's charge, that no second-row atom breaks the octet, that every structure is connected, and that the stated oxidation number is reproduced by the standard rules. Every resonance form is re-checked the same way. Every ionic formula this page builds is verified to balance to zero charge, and every precipitation equation it writes is verified to balance atom by atom. Two thousand assertions run on each build, and the build fails if any of them break.

Two places where chemistry itself is unsettled, and what this page does about them. Sulfate, phosphate, perchlorate and their relatives are drawn here with double bonds so that formal charges are minimised. Many courses instead require all-single-bond structures that keep the central atom at a strict octet, putting a positive formal charge on it. Both conventions are in current textbooks. Every affected ion is flagged on its anatomy page so you can match whichever your instructor wants. Solubility rules also vary slightly between texts — calcium sulfate and silver acetate are the usual disagreements — so borderline cases are marked rather than asserted.

This is a study tool, not a lab reference. Nothing here replaces a safety data sheet or your instructor.

Obsidian Clad Labs Built for a chemistry undergraduate, by their father