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List of Common Polyatomic Ions

Common Polyatomic Ions

Learning the common polyatomic ions is a right of passage for all chemistry classes. The good news, is that many of these ions are really cool, reactive, and or 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

Acetate C2H3O2
Ammonium NH4+
Bicarbonate HCO3 (Hydrogen Carbonate)
Carbonate CO3-2
Cyanide CN
Hydrogen Sulfate HSO4 (Bisulfate)
Hydroxide OH
Nitrate NO3
Nitrite NO2
Peroxide O2-2
Phosphate PO4-3
Sulfate SO4-2
Sulfite SO3-2

Less Common Polyatomic Ions

Arsenate AsO4-3
Borate BO4-3 (Orthoborate)
Bromate BrO3
Chlorate ClO3
Chlorite ClO2
Chromate CrO4-2
Citrate C6H5O7-3
Dihydrogen Phosphate H2PO4
Ferricyanide Fe(CN)6-3
Ferrocyanide Fe(CN)6-4
Formate HCO2
Monohydrogen Phosphate HPO4-2
Hydrogen Sulfite HSO3 (Bisulfite)
Hypochlorite ClO
Dichromate Cr2O7-2
Iodate IO3
Mercury (I) Hg2+2 (Mercurous)
Oxalate C2O4-2
Perchlorate ClO4
Permanganate MnO4
Phosphite PO3-3
Metasilicate SiO3-2
Thiocyanate SCN
Thiosulfate S2O3-2
Tungstate WO4-2

Polyatomic Ions – fun facts

  • Thiocyanate ion is used as a sensitive test for Fe+3
  • There are many different silicate ions, with different quantities of Si and O
  • Chlorates and Perchlorates are often used in explosives
  • Dichromates are often colored a brilliant yellow
  • 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

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