Names and Formulas of Common Ions
Monoatomic anions : negatively charged ions consisting of a single atom of one element (usually a nonmetal). To name a
monoatomic anion, use the stem of the element's name and add the ending "-ide ".
Group 14 nonmetals
Group 15 nonmetals
4- charge
C
4-
Si
3- charge
3-
carbide
4-
Group 16 nonmetals
3-
silicide
2- charge
nitride
N
phosphide
P
3-
arsenide
As
Group 17 nonmetals
O
2-
oxide
22-
fluoride
F
sulfide
S
Se
1- charge
-
Cl
selenide
-
chloride
-
bromide
Br
-
iodide
H-
hydride
I
Not a Group 17 element, but it
can make a 1- charge!
Nonmetal Oxyanions (polyatomic anions) : These negatively charged ions consist of more than one element (usually oxygen with
another nonmetal). The most common form of any oxyanion is named by using the stem of the nonmetal's name and adding the
ending "-ate ".
Group 14 nonmetals
CO32SiO32-
Group 15 nonmetals
carbonate
NO3-
silicate
PO43AsO43-
Group 16 nonmetals
nitrate
SO42-
phosphate
SeO42-
Group 17 nonmetals
sulfate
ClO3-
chlorate
selenate
BrO3IO3-
bromate
arsenate
iodate
If a polyatomic anion has one less oxygen than the most common form, the ending is changed from "-ate " to "-ite " without changing
the negative charge. (Think: "-ite" is oxygen "lite"!)
Group 14 nonmetals
CO 3
2-
Group 15 nonmetals
NO 3
carbonate
NO2PO 4 3PO33AsO 4 3AsO33-
No "-ite" form
SiO 3
2-
-
silicate
No "-ite" form
Group 16 nonmetals
2-
nitrate
SO 4
nitrite
SO32SeO 4 2SeO32-
phosphate
phosphite
Group 17 nonmetals
sulfate
ClO 3 -
chlorate
sulfite
ClO2BrO 3 BrO2IO 3 IO2-
chlorite
selenate
selenite
arsenate
arsenite
bromate
bromite
iodate
iodite
Polyatomic oxyanions with halogens can exist in four different forms, depending on the number of oxygens present. To name the
most common form of the anion, use the stem of the halogen's name and add the ending "-ate ". If the oxyanion has one less oxygen
than the most common form, the ending changes from "-ate " to "-ite ". If there is one less oxygen than the "-ite " anion, add the
prefix "hypo -" to the beginning of the "-ite " anion's name. If there is one more oxygen than the most common anion (the "-ate "
anion), add the prefix "per -" to the beginning of the "-ate " anion's name.
ClO4ClO 3
-
ClO2ClO
BrO4-
perchlorate
-
chlorate
BrO 3
chlorite
BrO2BrO
hypochlorite
perbromate
IO4-
periodate
bromate
IO 3
-
iodate
bromite
IO2-
iodite
hypobromite
IO
hypoiodite
Metal oxyanions : Some polaytomic oxyanions contain a metal instead of a nonmetal. These ions are named by adding the
suffix "-ate " to the stem of the metal name.
CrO42Cr2O72-
chromate
MnO4-
permanganate
dichromate*
MnO42-
manganate
*The prefix "di-" indicates 2
chromium atoms!
Note the difference in these two ions: same
formula, but different charges!
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Names and Formulas of Common Ions
Adding hydrogen to nonmetal oxyanions : When a hydrogen ion (H+) is added to an oxyanion, the charge of the oxyanion becomes
less negative by one. The new anion is named by adding the word "hydrogen " before the name of the original oxyanion (or by adding
the prefix "bi -"). If two hydrogens area added to an oxyanion, the charge will become less negative by two and the word
"dihydrogen " is added in front of the original oxyanion's name.
Group 14 elements
CO 3
2-
Group 15 elements
PO 4
carbonate
HCO3-
3-
SO 4
phosphate
hydrogen phosphate
HPO42H2PO4-
hydrogen carbonate
(or bicarbonate)
Group 16 elements
2-
HSO4-
sulfate
hydrogen sulfate
(or bisulfate)
SO 3 2HSO3-
sulfite
hydrogen sulfite
dihydrogen phosphate
3-
PO 3
HPO32H2PO3-
phosphite
hydrogen phosphite
dihydrogen phosphite
Other polyatomic ions: There are a few polyatomic anions that don't fit into any of the previous categories and have been given
"common" names. It's best to try to commit these ions to memory!
1- charge
C2H3O2-
2- charge
O22-
acetate
hydroxide
OH
CN-
*Look for the subscript to
tell the difference between
O 2- (oxide ion)
and O 2 2- (peroxide ion)!
cyanide
-
cyanate
-
thiocyanate
CNO
SCN
peroxide
Monoatomic cations : positively charged ions consisting of a single atom of one element (usually a metal). There are two categories of
monoatomic cations: cations with a single (or set) charge, and cations with variable charges.
To name a monoatomic ion with a set charge, name the element and add the word "ion " to show that there is a charge.
Group 1 elements
1+ charge
H+
Li
hydrogen ion
+
K
Mg
2+
sodium ion
Na
Ca
potassium ion
+
rubidium ion
+
cesium ion
Rb
Cs
Be2+
2+
lithium ion
+
+
Group 2 elements
2+ charge
Sr
Other cations with
set charges
magnesium ion
strontium ion
2+
barium ion
aluminum ion
2+
zinc ion
2+
cadmium ion
+
silver ion
Zn
calcium ion
2+
Ba
Al3+
beryllium ion
Cd
Ag
Some metals,especially the transition metals, can form more than one type of ion, each having a different charge. These charges can
be difficult to predict from the periodic table, so they are indicated by using Roman numerals as part of the name.
Co2+
+
Cu
cobalt (II) ion
Co3+
cobalt (III) ion
copper (I) ion
2+
copper (II) ion
3+
iron (III) ion
lead (IV) ion
Cu
2+
iron (II) ion
Fe
Pb2+
lead (II) ion
Pb4+
Fe
2+
Sn
Mn2+
4+
tin (II) ion
Sn
Hg2+
mercury (II) ion
Hg22+
mercury (I) ion*
*Exception - mercury (I) ion is actually a diatomic ion
(two atoms), not monoatomic. Look for the subscript to tell the
difference between mercury (I) and mercury (II)!
tin (IV) ion
manganese (III) ion
manganese (IV) ion
Mn3+
Mn4+
Mn6+
Manganese can form several different cations - these are the four most common forms.
manganese (II) ion
manganese (VI) ion
Polyatomic cations : Most polyatomic ions are negatively charged anions - there are only two common polyatomic cations.
NH4+
ammonium ion
H3O+
hydronium ion
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