Summary of Nomenclature
To correctly name a compound, you must first identify whether it is ionic, molecular or an acid.
Ionic compounds are composed of metals and non-metals.
Molecular compounds are composed of non-metals.
Acids have one or more hydrogens bound to an anion. The hydrogens dissociate from the anion when placed in
water.
You should be able to provide the name if given the chemical formula AND be able to provide the chemical
formula if given the name.
Ionic Compounds
An ionic compound is composed of a cation and an anion.
Metals lose electrons to form cations. Non-metals gain electrons to form anions.
Cations: There are three classes of cations, type 1, type 2, and polyatomic.
Type 1 cations form only one cation (only 1 charge/oxidation state)
Type 2 cations form more than one cation (more than 1 charge/oxidation state)
Polyatomic cations are composed of more than 2 or more atoms bound together by a covalent bond.
Type 1 cations include
+
+
+
+
+
a) Group 1A elements – Li , Na , K , Rb , Cs
2+
2+
2+
2+
2+
b) Group 2A elements – Be , Mg , Ca , Sr , Ba
3+
3+
c) Some group 3A elements – Al , Ga ,
3+
3+
3+
d) Some group 3B elements – Sc , Y , La
2+
2+
+
e) others – Zn , Cd , Ag
To name a type 1 cation add the word ion after the element name.
Ex.
+
K
2+
Sr
3+
Ga
potassium ion
strontium ion
gallium ion
Type 2 cations include the rest of the elements, primarily the transition metals and metals in the lower periods
of groups 3A through 6A.
To name a type 2 cation, include the charge of the ion and add ion after the element name.
Ex.
2+
Co
4+
Mo
+7
Mn
cobalt (II) ion
molybdenum (IV) ion
manganese (VII) ion
+
2+
Polyatomic cations include the ammonium ion (NH4 ) and the mercury (I) ion Hg2 . In addition, there is the
+
+
phosphonium ion (PH4 ) and the hydronium (H3O ).
Anions: There are two classes of anions, single atom (monoatomic) non-metals and polyatomic anions.
Monoatomic anions are formed from group 4A through 7A elements.
To name a monoatomic anion, add the suffix –ide to the root of the element and add the word ion.
Group 7A
F
Cl
Br
I
-
fluoride ion
chloride ion
bromide ion
iodide ion
Group 6A
O
2S
2Se
2Te
2-
oxide ion
sulfide ion
selenide ion
telluride ion
Group 5A
N
3P
3As
3-
nitride ion
phosphide ion
arsenide ion
Polyatomic anions are of two general types, the oxoanions and the “others”. The ones you need to know are
included in the table at the end of this handout. You need to know their formula, their charge, and their name.
The general rules for polyatomic oxoanions:
add the suffix ate to the stem of the name of the element other than oxygen, then add ion.
if an element forms two oxoanions, differing by the number of oxygens in the anion, use –ate as the
suffix for the anion with the most oxygens and –ite for the suffix for the anion with the fewer
oxygens.
Cl, Br, and I form a series of 4 oxoanions. Add the prefix per- to the oxoanion with the most oxygens
and the prefix hypo- to the oxoanion with the least oxygens.
if the oxoanion contains a hydrogen, add hydrogen to the beginning of the oxoanion name
Ionic compounds: Ionic compounds are neutral so the total charge must add up to zero.
(number of cations)(charge on cation) + (number of anions)(charge on anion)
To name an ionic compound, name the cation first and the anion second. Do not include the word ion.
Remember for a type II cation, the charge on the cation is part of the name.
Molecular Compounds
These compounds are composed of non-metals. The elements are held together by covalent bonds. You will
be responsible for naming binary compounds, compounds composed of two elements.
To name molecular compounds:
name the elements in the order they appear
add the suffix –ide to the stem name of the second element
use prefixes to indicate the number of atoms
do not add mono to the first element
when two “o”s appear, you need write only 1
when an a in the prefix is followed by an o, you use only the o
Acids
Acids fall into two general categories, those containing oxygen and those that do not contain oxygen.
To name acids that do not contain oxygen, add the prefix hydro- to the stem of the element name that is not
hydrogen and add the suffix –ic. Finally, add the word acid.
To name acids that contain oxygen, add the suffix –ic, if the anion ends in ate and add the suffix – ous, if the
anion ends in ite. Finally, add the word acid.
Some examples of mistakes to avoid:
-
-
Br is the bromide ion; BrO3 is the bromate ion
33P is the phosphide ion; PO4 is the phosphate ion
Learn the list of type I cations
Note the use of parenthesis in the following example:
ammonium carbonate (NH4)(CO3)2
Note the difference in the following acids:
HBrO4 is perbromic acid
HBr is hydrobromic acid
HBrO2 is bromous acid
Some practice problems:
Chemical formula to name
Name to chemical formula
a) LiH2PO4
b) Co2(SO3)3
c) Zn(CN)2
d) HCN
e) ICl3
f) Hg2S
a) chromium (III) carbonate
b) strontium nitride
c) cesium hypochlorite
d) barium arsenate
e) gallium nitride
f) sodium phosphide
Answers:
a) lithium dihydrogen phosphate
b) cobalt (III) sulfite
c) zinc cyanide
d) hydrogen cyanide
e) iodine trichloride
f) mercury (I) sulfide
a) Cr2(CO3)3
b) Sr3N2
c) CsClO
d) Ba3(AsO4)2
e) GaN
f) Na3P
Ion Category
Ion Formula
Group IV A
CO3
2SiO3
NO3
NO2
3PO4
3AsO4
3AsO3
3SbO4
2SO4
2SO3
2SeO4
2SeO3
2TeO4
2TeO3
ClO4
ClO3
ClO2
ClO
BrO4
BrO3
BrO2
BrO
IO4
IO3
IO2
IO
CH3COO or
C2H3O2
2C2O4
HCO3
Group V A
Group VI A
Group VII A
Organic Ions
Protonated
oxoanions
2-
-
HSO4
HSO3
2HPO4
-
H2PO4
Others
-
CN
CNO
CNS
OH
2CrO4
2Cr2O7
MnO4
2MnO4
2S2O3
Ion Name
Acid Formula
Acid Name
carbonate ion
siliconate ion
nitrate ion
nitrite ion
phosphate ion
arsenate ion
arsenite ion
antimonate ion
sulfate ion
sulfite ion
selenate ion
selenite ion
tellurate ion
tellurite ion
perchlorate ion
chlorate ion
chlorite ion
hypochlorite ion
perbromate ion
bromate ion
bromite ion
hypobromite ion
periodate ion
iodate ion
iodite ion
hypoiodite ion
acetate ion
H2CO3
carbonic acid
HNO3
HNO2
H3PO4
nitric acid
nitrous acid
phosphoric acid
H2SO4
H2SO3
H2SeO4
H2SeO3
sulfuric acid
sulfurous acid
selenic acid
selenous acid
HClO4
HClO3
HClO2
HClO
HBrO4
HBrO3
HBrO2
HBrO
HIO4
HIO3
HIO2
HIO
CH3COOH or
HC2H3O2
H2C2O4
perchloric acid
chloric acid
chlorous acid
hypochlorous acid
perbromic acid
bromic acid
bromous acid
hypobromous acid
periodic acid
iodic acid
iodous acid
hypoiodous acid
acetic acid
HCN
hydrocyanic acid
H2CrO4
H2Cr2O7
chromic acid
dichromic acid
oxalate ion
hydrogen carbonate
hydrogen sulfate
hydrogen sulfite
hydrogen
phosphate
dihydrogen
phosphate
cyanide ion
cyanate ion
thiocyanate ion
hydroxide ion
chromate ion
dichromate ion
permanganate ion
manganate ion
thiosulfate ion
oxalic acid