TABLE OF COMMON IONS (You need to memorize the ones in bold type.)
POSITIVE IONS (Cations)
+1
ammonium (NH4+)
cesium (Cs+)
copper (I) (Cu+)
gold(I) (Au+)
hydrogen (H+)
lithium (Li+)
potassium (K+)
rubidium (Rb+)
silver (Ag+)
sodium (Na+)
NEGATIVE IONS (Anions)
-1
acetate (C2H3O2- or CH3COO-)
bromate (BrO3-)
bromide (Br-)
chlorate (ClO3-)
chloride (Cl-)
chlorite (ClO2-)
cyanate (CNO-)
cyanide (CN-)
dihydrogen phosphate (H2PO4-)
fluoride (F-)
hydrogen carbonate (HCO3-)
hydrogen sulfate (HSO4-)
hydrogen sulfite (HSO3-)
hydroxide (OH-)
hypochlorite (ClO-)
hypobromite (BrO-)
iodate (IO3-)
iodide (I-)
nitrate (NO3-)
nitrite (NO2-)
perchlorate (ClO4-)
periodate (IO4-)
permanganate (MnO4-)
thiocynate (SCN-)
+2
barium (Ba2+)
beryllium (Be2+)
cadmium (Cd2+)
calcium (Ca2+)
chromium (II) (Cr2+)
cobalt (II) (Co2+)
copper (II) (Cu2+)
iron (II) (Fe2+)
lead (II) (Pb2+)
magnesium (Mg2+)
manganese (II) (Mn2+)
mercury (I) (Hg22+)
mercury (II) (Hg2+)
nickel (II) (Ni2+)
platinum (II) (Pt2+)
strontium (Sr2+)
tin (II) (Sn2+)
zinc (Zn2+)
+3
aluminum (Al3+)
chromium (III) (Cr3+)
cobalt (III) (Co3+)
gallium (Ga3+)
gold (III) (Au3+)
iron (III) (Fe3+)
nickel (III) (Ni3+)
+4
lead (IV) (Pb4+)
manganese (IV) (Mn4+)
platinum (IV) (Pt4+)
tin (IV) (Sn4+)
-2
carbonate (CO32-)
chromate (CrO42-)
dichromate (Cr2O72-)
hydrogen phosphate (HPO42-)
oxalate (C2O42-)
oxide (O2-)
peroxide (O22-)
selenide (Se2-)
silicate (SiO32-)
sulfate (SO42-)
sulfide (S2-)
sulfite (SO32-)
telluride (Te2-)
thiosulfate (S2O32-)
-3
arsenate (AsO43-)
borate (BO33-)
nitride (N3-)
phosphate (PO43-)
phosphide (P3-)
Use the following discussion notes to help you learn the names and formulas of monatomic and polyatomic
ions.

Monatomic Ions
o All monatomic ions in group 1 are (+1)
o All monatomic ions in group 2 are (+2)
o All nonmetallic monatomic ions in group 15 are (-3)
o All nonmetallic monatomic ions in group 16 are (-2)
o All monatomic ions in group 17 are (-1)
o All metallic monatomic ions in group 13 are (+3) unless the name contains a Roman numeral
that indicates the charge.
o Most metallic ions in groups 3-16 have multiple charges. The charge on these metals that
have multiple monatomic ions will be indicated by using a Roman numeral (in the name
only) that is equivalent to the charge. Metals that have only one monatomic ion do not
have Roman numerals in their name.
 Polyatomic ions
o All ions to be memorized end in (-ate). Exceptions: hydroxide, peroxide, cyanide.
o Three very important ions that you memorized are models for similar polyatomic ions in
their corresponding groups. These ions are limited to Groups 15-17 and periods 3, 4 and 5.
Note that the charges on these ions are the same as the groups listed above.
 Group 15 - Phosphate (arsenate, antimonate) , XO43 Group 16 - Sulfate (selenate, tellurate) , XO42 Group 17 - Chlorate (bromate, iodate) , XO31o All ions that end in (-ite) have a charge equal to the corresponding (-ate) ion but contain one
less oxygen atom.
o All ions that have one less oxygen atom than those ending in (-ite) have the prefix hypoadded to the (-ite) name. Their charge remains the same as the (-ite). Remember that hypomeans lower or under.
o All ions that have one more oxygen atom than those ending in (-ate) have the prefix peradded to the (-ate) name. Their charge remains the same as the (-ate). Per- is an
abbreviated form of the word hyper- which means more or over.
o (*) Polyatomic ions that have -2 or -3 charges may have one hydrogen ion (H+) added to form
a new polyatomic ion. The name and the charge on these new ions are a composite of
hydrogen ion and the original polyatomic ion. The hydrogen ion, H+, attached to the
carbonate ion, CO32-, to become the hydrogen carbonate ion, HCO31-. Note: It is still
common for people to call these new polyatomic ions using the prefix bi- instead of the word
hydrogen, bicarbonate instead of hydrogen carbonate.
o (*) Polyatomic ions that have -3 charge may have two hydrogen ion (H+) added to form a
new polyatomic ion. The name and the charge on these new ions are a composite of the
two hydrogen ions and the original polyatomic ion. Two hydrogen ions, 2 H+, attached to the
phosphate ion, PO43-, to become the dihydrogen phosphate ion, H2PO41-.
(*) Note that these new entities are ions and not compounds. A compound has no charge. When anions
(negative ions) combine with hydrogen ions to form compounds, the compounds are generally named as
acids.