Common Ions and Their Charges
Reference table of common monatomic and polyatomic ions with their charges and formulas. Essential for writing chemical formulas and naming compounds.
Common Monatomic and Polyatomic Ions
Names, formulas, and charges for writing and naming ionic compounds.
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| Sodium | Na+ | +1 | Monatomic cation |
| Potassium | K+ | +1 | Monatomic cation |
| Lithium | Li+ | +1 | Monatomic cation |
| Silver | Ag+ | +1 | Monatomic cation |
| Ammonium | NH4+ | +1 | Polyatomic cation |
| Magnesium | Mg2+ | +2 | Monatomic cation |
| Calcium | Ca2+ | +2 | Monatomic cation |
| Barium | Ba2+ | +2 | Monatomic cation |
| Strontium | Sr2+ | +2 | Monatomic cation |
| Zinc | Zn2+ | +2 | Monatomic cation |
| Iron(II) | Fe2+ | +2 | Monatomic cation |
| Iron(III) | Fe3+ | +3 | Monatomic cation |
| Copper(I) | Cu+ | +1 | Monatomic cation |
| Copper(II) | Cu2+ | +2 | Monatomic cation |
| Aluminum | Al3+ | +3 | Monatomic cation |
| Lead(II) | Pb2+ | +2 | Monatomic cation |
| Mercury(I) | Hg22+ | +2 (pair) | Polyatomic cation |
| Mercury(II) | Hg2+ | +2 | Monatomic cation |
| Fluoride | F- | -1 | Monatomic anion |
| Chloride | Cl- | -1 | Monatomic anion |
| Bromide | Br- | -1 | Monatomic anion |
| Iodide | I- | -1 | Monatomic anion |
| Oxide | O2- | -2 | Monatomic anion |
| Sulfide | S2- | -2 | Monatomic anion |
| Nitride | N3- | -3 | Monatomic anion |
| Hydroxide | OH- | -1 | Polyatomic anion |
| Nitrate | NO3- | -1 | Polyatomic anion |
| Nitrite | NO2- | -1 | Polyatomic anion |
| Sulfate | SO42- | -2 | Polyatomic anion |
| Sulfite | SO32- | -2 | Polyatomic anion |
| Hydrogen sulfate | HSO4- | -1 | Polyatomic anion |
| Thiosulfate | S2O32- | -2 | Polyatomic anion |
| Carbonate | CO32- | -2 | Polyatomic anion |
| Hydrogen carbonate (bicarbonate) | HCO3- | -1 | Polyatomic anion |
| Phosphate | PO43- | -3 | Polyatomic anion |
| Hydrogen phosphate | HPO42- | -2 | Polyatomic anion |
| Dihydrogen phosphate | H2PO4- | -1 | Polyatomic anion |
| Acetate | CH3COO- | -1 | Polyatomic anion |
| Permanganate | MnO4- | -1 | Polyatomic anion |
| Chromate | CrO42- | -2 | Polyatomic anion |
| Dichromate | Cr2O72- | -2 | Polyatomic anion |
| Perchlorate | ClO4- | -1 | Polyatomic anion |
| Chlorate | ClO3- | -1 | Polyatomic anion |
| Chlorite | ClO2- | -1 | Polyatomic anion |
| Hypochlorite | ClO- | -1 | Polyatomic anion |
| Cyanide | CN- | -1 | Polyatomic anion |
| Oxalate | C2O42- | -2 | Polyatomic anion |
| Thiocyanate | SCN- | -1 | Polyatomic anion |
Important Notes
- Group 1 metals (Li, Na, K, Rb, Cs) always form +1 ions.
- Group 2 metals (Be, Mg, Ca, Sr, Ba) always form +2 ions.
- Transition metals often form multiple ion charges (e.g., Fe²⁺ and Fe³⁺). Use Roman numerals in names.
- The -ate suffix generally indicates more oxygen atoms; -ite indicates fewer (e.g., sulfate SO₄²⁻ vs sulfite SO₃²⁻).
- The per- prefix means one more oxygen than -ate; hypo- prefix means one fewer than -ite.
- Mercury(I) is unusual: it exists as a diatomic ion Hg₂²⁺, not as a simple Hg⁺.