Common Polyatomic Ions
Reference table of polyatomic ions organized by charge, with naming conventions and patterns.
Positive Ions (+1)
| Name | Formula | Charge |
|---|---|---|
| Ammonium | NH₄⁺ | +1 |
| Hydronium | H₃O⁺ | +1 |
Negative Ions (\u22121)
| Name | Formula | Charge |
|---|---|---|
| Acetate | C₂H₃O₂⁻ (CH₃COO⁻) | −1 |
| Bicarbonate | HCO₃⁻ | −1 |
| Bisulfate | HSO₄⁻ | −1 |
| Chlorate | ClO₃⁻ | −1 |
| Chlorite | ClO₂⁻ | −1 |
| Cyanide | CN⁻ | −1 |
| Dihydrogen phosphate | H₂PO₄⁻ | −1 |
| Hydroxide | OH⁻ | −1 |
| Hypochlorite | ClO⁻ | −1 |
| Nitrate | NO₃⁻ | −1 |
| Nitrite | NO₂⁻ | −1 |
| Perchlorate | ClO₄⁻ | −1 |
| Permanganate | MnO₄⁻ | −1 |
| Thiocyanate | SCN⁻ | −1 |
Negative Ions (\u22122)
| Name | Formula | Charge |
|---|---|---|
| Carbonate | CO₃²⁻ | −2 |
| Chromate | CrO₄²⁻ | −2 |
| Dichromate | Cr₂O₇²⁻ | −2 |
| Hydrogen phosphate | HPO₄²⁻ | −2 |
| Oxalate | C₂O₄²⁻ | −2 |
| Peroxide | O₂²⁻ | −2 |
| Sulfate | SO₄²⁻ | −2 |
| Sulfite | SO₃²⁻ | −2 |
| Thiosulfate | S₂O₃²⁻ | −2 |
Negative Ions (\u22123)
| Name | Formula | Charge |
|---|---|---|
| Phosphate | PO₄³⁻ | −3 |
| Phosphite | PO₃³⁻ | −3 |
Naming Patterns
Polyatomic ion names follow systematic patterns relating the number of oxygen atoms to the suffix and prefix used.
Chlorine Oxyanion Series
-ate → -ic acid
An ion ending in -ate corresponds to an acid ending in -ic acid.
Sulfate (SO₄²⁻) → Sulfuric acid (H₂SO₄)
-ite → -ous acid
An ion ending in -ite corresponds to an acid ending in -ous acid.
Sulfite (SO₃²⁻) → Sulfurous acid (H₂SO₃)
per-...-ate = one more O than -ate
The per- prefix indicates one additional oxygen atom compared to the -ate form.
Perchlorate (ClO₄⁻) vs. Chlorate (ClO₃⁻)
hypo-...-ite = one fewer O than -ite
The hypo- prefix indicates one fewer oxygen atom compared to the -ite form.
Hypochlorite (ClO⁻) vs. Chlorite (ClO₂⁻)
Related Tools & References
Formulas use IUPAC-recommended names. For a complete list of ions in aqueous solution, consult the IUPAC Compendium of Chemical Terminology (Gold Book).