List of Common Polyatomic Ions

Names, Formulas and Charges of Polyatomic Ions

This is a list of some of the most common polyatomic ions. It is worth committing the polyatomic ions to memory, including their molecular formulas and ionic charge.

01
of 04
Polyatomic Ion Charge = +1

ammonium ion
This is the structure of an ammonium ion. Todd Helmenstine

Polyatomic ions with a positive 1 charge do occur, but the main one you'll encounter and need to know is the ammonium ion.

ammonium - NH4+

02
of 04
Polyatomic Ion Charge = -1

chlorate anion
This is the one of the resonant structures of the chlorate anion. Ben Mills/PD

Many of the common polyatomic ions have an electrical charge of -1. It's good to know these ions on sight to help balance equations and predict compound formation.

acetate - C2H3O2-
bicarbonate (or hydrogen carbonate) - HCO3-
bisulfate (or hydrogen sulfate) - HSO4-
hypochlorite - ClO-
chlorate - ClO3-
chlorite - ClO2-
cyanate - OCN-
cyanide - CN-
dihydrogen phosphate - H2PO4-
hydroxide - OH-
nitrate - NO3-
nitrite - NO2-
perchlorate - ClO4-
permanganate - MnO4-
thiocyanate - SCN-

03
of 04
Polyatomic Ion Charge = -2

thiosulfate anion
This is the chemical structure of the thiosulfate anion. Todd Helmenstine

Polyatomic ions with a minus 2 charge are also common.

carbonate - CO32-
chromate - CrO42-
dichromate - Cr2O72-
hydrogen phosphate - HPO42-
peroxide - O22-
sulfate - SO42-
sulfite - SO32-
thiosulfate - S2O32-

04
of 04
Polyatomic Ion Charge = -3

phosphate anion
This is the chemical structure of the phosphate anion. Todd Helmenstine

Of course, several other polyatomic ions form with the negative 3 charge, but the borate and phosphate ions are the ones to memorize.

borate - BO33-
phosphate - PO43-