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.
| Ion Name | Formula | Charge | Type |
|---|---|---|---|
| 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 |
| 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⁺.