Learning the common polyatomic ions is a rite of passage for all chemistry students. The good news is that many of these ions are really cool, reactive, and colorful. So let’s jump right in and look at the list of common polyatomic ions. Afterwards, we’ll share some cool facts about these ions, and talk about some not-so-common ones. If you haven’t yet, review our article on cations and anions.
Covered in other articles:
Cations and Anions
Naming Ionic Compounds
List of Strong Acids & Bases
Most Common Polyatomic Ions
List of the polyatomic ions you will see most often. Be sure to know these by heart!
Bicarbonate HCO3– (Hydrogen Carbonate)
Bisulfate HSO4– (Hydrogen Sulfate)
Less Common Polyatomic Ions
The ions in this list, although less common than the first list, are still seen quite frequently in chemistry – so we suggest you learn these as well.
Borate BO33- (Orthoborate)
Dihydrogen Phosphate H2PO4–
Monohydrogen Phosphate HPO42-
Hydrogen Sulfite HSO3– (Bisulfite)
Mercury (I) Hg22+ (Mercurous)
Polyatomic Ions list of fun facts
- Thiocyanate ion is used as a sensitive test for Fe3+ – Iron (III) thiocyanate is very red, even in small concentrations
- There are many different silicate ions, with different quantities of Si and O; the same is true of molybdates
- Chlorates and Perchlorates are often used in explosives
- Dichromates are often colored a brilliant yellow, but are also considered carcinogenic
- The mercury (I) ion, while still toxic, is less so than mercury (II)
- Ants use the formate ion as a weapon, in the form of formic acid
- Nitrate salts are universally soluble (inorganic ones; oxynitrates not included)
- Thiosulfate ion has a great use – cleaning iodine stains
- Some metal oxalates decompose when heated to form a pyrophoric elemental powder. Cool!
- The silicate ion can be used to form a chemical garden when colorful metal salts are added to the solution
- Sodium dihydrogen phosphate is also called monosodium phosphate. Yeah, confusing.
- Ferric ferrocyanide is used as an emergency cure for thallium poisoning
- Toxic ions like arsenate can be detected using arsenic speciation
- Sodium acetate can be used to produce hot ice
- Polyatomic ion lists can lead to a lifetime love of descriptive chemistry. Beware!