Nomenclature
Binary Compounds
There are three types of binary compounds that are named in three different ways.
1. Univalent metal and non-metal (simple method)
2. Multivalent metal and non-metal (IUPAC or OUS/IC system)
3. Two non-metals (prefix system)
Type 1: Univalent metal and a non-metal
This type of compound is made up of a metal with only one valence number (the alkali
metals, alkaline earth metals and some transition metals) and a non-metal.
Naming:
1. Name the metal
2. Name the non-metal with –ide suffix
i.e.
NaCl
MgF2
Formula:
1. Write the symbols for both elements
2. Write the valence number in the top right hand corner
3. Cross over rule
4. Simplify (if possible)
5.
Ex.
calcium iodide
magnesium oxide
Type 2: Multivalent Metal and a non-metal
This type of compound is made up of a metal that has more than one possible valence
number (transition metals and metals on the right side of the periodic table) and a nonmetal.
IUPAC System
There should be no confusion when naming a compound. It must be clear exactly which
valence value is being used. In this system, the valence for all multivalent elements is put as
a Roman Numeral in brackets after the first element’s name.
Naming:
1. Name the metal.
2. Using the cross over rule backwards, determine the balance numbers of both elements.
3. Verify that the non-metal’s valence is correct, multiply if necessary.
4. Write the metal’s valence number as a Roman numeral.
5. Name the non-metal with –ide suffix.
Ex.
Cu2O
NiCl3
FeS
Formula:
1. Write the symbols for both elements.
2. Write in the valence numbers.
3. Cross over rule.
4. Simplify (if possible)
Ex.
iron (III) chloride
chromium (III) oxide
The OUS/IC system of naming
You will only write the formula for these compounds because if you are writing a name, you
will always use the IUPAC name. This is the old way of naming compounds but is still used
by some scientists.
The following are the Latin names of multivalent metals:
Element
Latin
Electrovalence
Hg
Mercurous
1+
Mercuric
Cuprous
Cupric
Ferrous
Ferric
Stannous
Stannic
Plumbous
Plumbic
Manganous
Manganic
Arsenious
Arsenic
Antimonous
Antimonic
Cu
Fe
Sn
Pb
Mn
As
Sb
2+
1+
2+
2+
3+
2+
4+
2+
4+
2+
4+
3+
5+
3+
5+
Naming:
1. Using the cross over rule backwards, determine the valence numbers of BOTH elements.
2. Write the Latin name with the correct suffix.
-ic ending if the higher valence is used
-ous ending if the lower valence is used
3. Name the non metal with –ide ending
Ex.
stannic chloride
plumbous sulfide
Type 3: Two Non-metals
Many non-metals have positive valence values in addition to their one negative valence
value. In order to name using this system you need to know the following prefixes:
Prefix
MonoDiTri
Tetra
# of atoms
1
2
3
4
Prefix
PentaHexaHeptaOcta-
# of atoms
5
6
7
8
Naming:
1. Write the correct prefix for the first non-metal and it’s name
2. Write the prefix and name for the second non-metal
NOTE: mono- is not required for the first non-metal, but is needed for the second.
Ex.
CO
CO2
Formula:
1. Write the symbol for the first element, and write in the prefix in the formula (not as a
valence value).
2. Write the symbol for the second elements and the prefix number as part of the formula.
Ex.
nitrogen trichloride
dinitrogen tetraoxide
Radicals and Polyatomic Ions
Not all compounds are binary (containing only 2 elements) and are polyatomic. These
generally contain what is called a radical group. Each radical group is a number of atoms
which hang around together in a group. The group reacts as an element (i.e. the group
remains unchanged during a chemical reaction) and the group has a single oxidation number
and name.
The key to understanding radicals is knowing the five oxy-acids listed above. The radical
group is each of the acids above without the hydrogens. The oxidation number is equal to
the number of H’s that were there. These radicals are then used in other compounds and
must become electrically neutral (by cross over rule).
Table of Radicals (Note it’s similarity to the oxy acids table)
- 2 Oxygens
- 1 Oxygen
Hypo…ite
NO1Hyponitrite
i.e.
-ite
ate
+ 1 Oxygen
Per…..ate
NO21Nitrite
NO31NO41Nitrate
Pernitrate
1ClO3
Chlorate
BrO31Bromate
IO31Iodate
CO32Carbonate
SO42Sulfate
PO43Phosphate
H3PO4 phosphoric acid becomes PO43- phophate ion reacts with
Na1+ to form Na3PO4 (sodium phosphate)
Other Radicals
Name
Formula
Name
Formula
Hydroxide
OH1-
Bicarbonate
HCO31-
Acetate
CH3COO1-
Bisulfate
HSO41-
Chromate
CrO42-
Biphosphate
HPO42-
Cyanide
CN1-
Thiocyanate
SCN1-
Ammonium
NH41-
Permanganate
MnO41-