polyatomic ion

Polyatomic Ions.table

List of Polyatomic Ions that
Must be Memorized for General Chemistry
Polyatomic Cation: NH4+ ammonium ion
Polyatomic Anions
Ionic Charge:
Oxyanions:
ClO4– perchlorate ion
ClO3–
chlorate ion
–
ClO2 chlorite ion
ClO–
hypochlorite ion

-1

Ionic Charge:

Oxyanions that Contain
Hydrogen:
HCO3– bicarbonate ion or hydrogen carbonate ion
HSO4–
bisulfate ion or hydrogen sulfate ion

NO3–
NO2–

nitrate ion nitrite ion

MnO4–

permanganate ion

H2PO4–
Others:
CN–

dihydrogen phosphate ion cyanide ion

OH–

hydroxide ion

SCN–

thiocyanate ion

C2H3O2– acetate ion
(Often written as CH3COO–)

-2

Oxyanions:
CO32–
carbonate ion
SO42–
SO32–

sulfate ion sulfite ion

CrO42–
Cr2O72–
C2O42–
S2O32–

chromate ion dichromate ion oxalate ion thiosulfate ion

Oxyanions that Contain
Hydrogen:
HPO42– hydrogen phosphate ion
Others:
O22–

peroxide ion

Ionic Charge:

-3

Oxyanion:
PO43–
phosphate ion

Some Notes and helpful hints:
•

Some textbooks refer to oxyanions as oxoanions. These are equivalent terms, meaning simply a polyatomic anion that consists of a central atom bonded to one or more oxygen atoms. •

Oxyanions have names ending in –ate or –ite. The ending –ate is used for the most common oxyanion. The ending –ite is used for an oxyanion that has the same charge, but one fewer oxygen. The prefixes per- and hypo- are used for a series of four oxyanions of an element.
The prefix per- indicates one more oxygen than the oxyanion ending in –ate. The prefix hypoindicates one less oxygen than the oxyanion ending in –ite.

•

When hydrogen is added to an oxyanion, it is actually an H+ that is added thus reducing the negative charge of the parent anion by one for each hydrogen that is added. These are named by adding hydrogen (for one hydrogen added) or dihydrogen (for two hydrogens added) in front of the name of the parent anion. Some of these also