Names of Ions
Monatomic Cation Examples
cation
You need to know ion names both this term
and in CHM 112. Use the Table of Ions on the
CHM 111 supplements page as a guide.!
There are several patterns in the naming that
may make the names easier to remember.
!
You should know these cations and the pair of
charges listed for each:!
!
copper (1+, 2+); !
iron (2+, 3+); !
chromium (2+, 3+); !
tin (2+, 4+); and !
lead (2+, 4+).!
Notice that the name of
each monatomic cation is
the same as the name of
the element. A roman
numeral indicates the
cation’s charge, when
there is more than one
possibility.
name!
Na1+
sodium ion !
Al3+
aluminum ion !
Mg2+ magnesium ion !
Fe3+
iron(III) ion !
Cu2+
copper(II) ion
Monatomic Anion Examples
anion
Notice that the name of
each monatomic anion is
formed by giving the name
of the element an -ide
ending.!
Ions with names ending
with -ate and -ite all
contain oxygen, but -ide
ions do not contain oxygen
unless “ox” is in their name.
name!
Cl1-
chloride ion!
S2-
sulfide ion!
F1-
fluoride ion!
P3-
phosphide ion!
O2-
oxide ion
Polyatomic Cation Examples
There are only two
polyatomic cations
you will need to
know this term.
Both have names
with -onium endings.
cation
name!
NH41+
ammonium ion!
H3O1+
hydronium ion!
Polyatomic Anion Suffixes
If ions with the same
central atom are compared,
we see that the -ite ion
has one less oxygen than
the -ate ion but the
charge is the same.
anion
name!
SO42-
sulfate ion!
SO32-
sulfite ion!
!
NO31-
nitrate ion!
NO21-
nitrite ion
Polyatomic Anion Examples
anion
There are a numerous
polyatomic anions. Most
have names with -ate or !
-ite suffixes indicating the
presence of oxygen in the
ion.!
The name clearly identifies
the central atom.
name!
PO43-
phosphate ion!
SO32-
sulfite ion!
CO32-
carbonate ion!
NO21-
nitrite ion
Polyatomic Anion Prefixes
anion
For a series having more
than two polyatomic
anions, prefixes are added
to form additional names.
The per- prefix indicates
one more oxygen and the
hypo- prefix is used for
one less oxygen.
ClO41-
name!
perchlorate ion!
ClO31-
chlorate ion!
ClO21-
chlorite ion!
ClO1-
hypochlorite ion
Polyatomic Anion Relationships
anion
Knowing the relationships
between ions of a series,
allows the whole series to
be determined from the
number of oxygens and
the charge for one of the
ions (typically the -ate
ion).
name!
1-
ClO4
perchlorate ion!
4 O’s (1 more), same charge!
ClO31chlorate ion!
3 O’s, 1- charge!
ClO21chlorite ion!
2 O’s (1 less), same charge!
ClO1- hypochlorite ion!
1 O (1 less than -ite) 1- chrg
Mnemonic for !
-ate Polyatomic Anions
URL for youtube video:!
http://www.youtube.com/watch?v=-iP2ifS4IUI!
Removing some ions we will not use we have!
“Nick the Camel ate a Clam for Supper in Phoenex.”!
This Mnemonic doesn’t include acetate, permanganate,
dihydrogen phosphate, hydrogen phosphate, hydrogen
carbonate, hydrogen sulfate.
Polyatomic Anions
Containing Hydrogen
Some polyatomic
ions contain
hydrogen. Each
hydrogen reduces
the charge of the
original ion by one.
Hydrogen becomes
part of the anion
name.
anion
SO42HSO41-
name!
sulfate ion!
hydrogen sulfate ion!
!
PO43phosphate ion!
HPO42hydrogen phosphate ion!
H2PO41- dihydrogen phosphate ion!
Polyatomic “-ide” Anions
Not all anions with names
ending in -ide are
monatomic. Three polyatomic
ions with -ide names are
shown at right. Remember
that most -ide ions do not
have oxygen. The few -ide
ions that do contain oxygen
have “ox” in their names.
anion
name!
OH1-
hydroxide ion!
CN1-
cyanide ion!
2-
peroxide ion
O2
Modern System Cation Names!
!
As mentioned earlier, these cations should be
named with roman numerals to indicate the charge:!
!
Old Names for Ions
copper (1+, 2+); !
iron (2+, 3+); !
chromium (2+, 3+); !
tin (2+, 4+); and !
lead (2+, 4+).!
I do not recommend that you name this way, but you
should be able to write formulas from these names.
!
ex. copper(I) ion for Cu1+!
!
Old System Cation Names!
The old way of designating charge used -ous and -ic
endings for lower and higher charge respectively:!
!
copper (1+, 2+); iron (2+, 3+); chromium (2+, 3+); !
tin (2+, 4+); and lead (2+, 4+).!
!
ex.
and
chromous ion for Cr2+ !
chromic ion for Cr3+!
Since -ous and -ic only indicate lower or higher, it is
necessary to remember the two likely charges for
these ions.!
!
The use of old, non-english names for some of the
elements makes this slightly more difficult to
recognize . Note how the chemical symbols for
copper (Cu), iron (Fe), tin (Sn), and lead (Pb) are
inconsistent with there modern english names. These
symbols are based on the old name of each element:!
!
copper (cuprum)!
iron (ferrum)!
tin (stannum) !
lead (plumbum)
Instead of ironous and ironic, the old ferrous (Fe2+)
and ferric (Fe3+) names are used.!
!
cupruous (Cu1+), cupric (Cu2+)!
ferrous (Fe2+), ferric (Fe3+)!
stannous (Sn2+), stannic (Sn4+)!
plumbous (Pb2+), plumbic (Pb4+)!
!
Our periodic table doesn’t have element names that
start with cupr, ferr, stann, or plumb. If you see the
ferric in the name of a substance and cannot find
ferr on the table, then you know it is a case where
the symbol for ferr doesn’t match the element name.
From there you come up with Fe for iron. Once it is
identified as iron, the -ic ending indicates 3+.!
!
ferrous (Fe2+), ferric (Fe3+); !
!
Modern Names for Polyatomic
Anions Containing Hydrogen
Some polyatomic
ions contain
hydrogen. Each
hydrogen reduces
the charge of the
original ion by one.
Hydrogen becomes
part of the anion
name.
anion
SO42HSO41-
name!
sulfate ion!
hydrogen sulfate ion!
!
PO43phosphate ion!
2HPO4
hydrogen phosphate ion!
H2PO41- dihydrogen phosphate ion!
Old Names for Polyatomic Anions
Containing Hydrogen
anion
Polyatomic ions with
one hydrogen and a
1- charge can be
named with a biprefix. The three
ion names that you
may see this term
are shown at right.
(It does not apply
to phosphate ions.)
SO42HSO41!
SO32HSO31!
SO42HSO41!
name!
sulfate ion!
bisulfate ion!
sulfite ion!
bisulfite ion!
carbonate ion!
bicarbonate ion!