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List of Common Polyatomic Ions

Common Polyatomic Ions

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

Acetate C2H3O2
Ammonium NH4+
Bicarbonate HCO3 (Hydrogen Carbonate)
Carbonate CO32-
Cyanide CN
Bisulfate HSO4 (Hydrogen Sulfate)
Hydroxide OH
Nitrate NO3
Nitrite NO2
Peroxide O22-
Phosphate PO43-
Sulfate SO42-
Sulfite SO32-

Less Common Polyatomic Ions

Arsenate AsO43-
Borate BO33- (Orthoborate)
Bromate BrO3
Chlorate ClO3
Chlorite ClO2
Chromate CrO42-
Citrate C6H5O73-
Dihydrogen Phosphate H2PO4
Ferricyanide Fe(CN)63-
Ferrocyanide Fe(CN)64-
Formate HCO2
Monohydrogen Phosphate HPO42-
Hydrogen Sulfite HSO3 (Bisulfite)
Hypochlorite ClO
Dichromate Cr2O72-
Iodate IO3
Mercury (I) Hg22+ (Mercurous)
Oxalate C2O42-
Perchlorate ClO4
Permanganate MnO4
Phosphite PO3-3
Metasilicate SiO32-
Thiocyanate SCN
Thiosulfate S2O32-
Tungstate WO42-

Polyatomic Ions – fun facts

  • Thiocyanate ion is used as a sensitive test for Fe3+
  • 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
  • Toxic ions like arsenate can be detected using arsenic speciation
  • Sodium acetate can be used to produce hot ice

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