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Common Ions
An ion is either a charged atom or group of atoms. A polyatomic ion is a molecule composed of multiple atoms that has a net charge and has internal chemical bonds so strong that it rarely breaks up during reactions, allowing it to be treated as a single discrete unit during equation balancing and related operations.
Anions (Negatively Charged)
A note on the table below: not all ions are listed. Prefixes (hypo-, per-) are omitted, as is the suffix "-ite." If you need to look up an ion with one of these prefixes or suffices, use the following basic rules. In some cases (for example, permanganate ion), an ion with a prefix is listed for it is the only common form.
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Start with the "-ate" form of an ion as a root.
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If the ion in question begins with "per-" then there is one more oxygen present in the ion than there is in the "-ate" form.
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If the ion in question ends in "-ite" without "hypo-" at the beginning, then there are one fewer oxygens than in the "-ate" form.
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If the ion in question ends in "-ite" and begins with "hypo-" then there are two fewer oxygens than in the "-ate" form.
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All of the prefixed or suffixed ions have the same charge as the root (-ate) form.
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Example: The hypochlorite ion is identical to the chlorate ion, but has two fewer oxygens. Thus, the formula is ClO -.
Cells are color-coded by charge.
| Name | Formula | Charge |
| acetate | CH3COO - | -1 |
| bicarbonate (hydrogen carbonate) | HCO3 - | -1 |
| bisulfate (hydrogen sulfate) | HSO4 - | -1 |
| bromate | BrO3 - | -1 |
| bromide | Br - | -1 |
| carbonate | CO3 2- | -2 |
| chlorate | ClO3 - | -1 |
| chloride | Cl - | -1 |
| chromate | CrO4 2- | -2 |
| cyanate | OCN - | -1 |
| cyanide | CN - | -1 |
| dichromate | Cr2O7 2- | -2 |
| dihydrogen phosphate | H2PO4 - | -1 |
| fluoride | F - | -1 |
| hydroxide | OH - | -1 |
| iodate | IO3 - | -1 |
| iodide | I - | -1 |
| nitrate | NO3 - | -1 |
| nitride | N 3- | -3 |
| oxalate | C2O4 2- | -2 |
| oxide | O 2- | -2 |
| permanganate | MnO4 - | -1 |
| phosphate | PO4 3- | -3 |
| sulfate | SO4 2- | -2 |
| sulfide | S 2- | -2 |
| thiocyanate | SCN - | -1 |
| thiosulfate | S2O3 2- | -2 |
Cations (Positively Charged)
A note on the table below: most transition metals have multiple oxidation states. The roman numerals in parentheses in names denotes the oxidation state of the particular ion. For example, iron (II) has an oxidation number of +2, while iron (III) has an oxidation number of +3.
Cells are color-coded by charge.
| Name | Formula | Charge |
| aluminum | Al 3+ | +3 |
| ammonium | NH4 + | +1 |
| barium | Ba 2+ | +2 |
| cadmium | Cd 2+ | +2 |
| calcium | Ca 2+ | +2 |
| cesium | Cs + | +1 |
| chromium (II) | Cr 2+ | +2 |
| chromium (III) | Cr 3+ | +3 |
| cobalt (II) | Co 2+ | +2 |
| cobalt (III) | Co 3+ | +3 |
| cobalt (IV) | Co 4+ | +4 |
| copper (I) | Cu + | +1 |
| copper (II) | Cu 2+ | +2 |
| gold (I) | Au + | +1 |
| gold (III) | Au 3+ | +3 |
| hydrogen {See note} | H + | +1 |
| hydronium {See note} | H3O + | +1 |
| iron (II) | Fe 2+ | +2 |
| iron (III) | Fe 3+ | +3 |
| lead (II) | Pb 2+ | +2 |
| lead (IV) | Pb 4+ | +4 |
| lithium | Li + | +1 |
| magnesium | Mg 2+ | +2 |
| manganese (II) | Mn 2+ | +2 |
| manganese (III) | Mn 3+ | +3 |
| manganese (VII) | Mn 7+ | +7 |
| mercury (I) {See note} | Hg2 2+ | +2 |
| mercury (II) | Hg 2+ | +2 |
| nickel (II) | Ni 2+ | +2 |
| nickel (IV) | Ni 4+ | +4 |
| potassium | K + | +1 |
| rubidium | Rb + | +1 |
| scandium (III) | Sc 3+ | +3 |
| silver | Ag + | +1 |
| sodium | Na + | +1 |
| tin (II) | Sn 2+ | +2 |
| tin (IV) | Sn 4+ | +4 |
| titanium (II) | Ti 2+ | +2 |
| titanium (III) | Ti 3+ | +3 |
| titanium (IV) | Ti 4+ | +4 |
| vanadium (II) | V 2+ | +2 |
| vanadium (III) | V 3+ | +3 |
| vanadium (IV) | V 4+ | +4 |
| zinc | Zn 2+ | +2 |
A note about mercury: mercury (I) is diatomic. Hg2 can generally be treated as a single unit.
Author: C. Shultz
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