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Chemical Names for Compounds
We will spend some time later in this course working with the intricacies of chemical
names. But there are a couple important things you should learn now. One is the reason for
having a systematic method for naming chemical compounds. The other is identifying the
elements contained in compounds, which is the first step in determining the formula and
composition of compounds.
| As chemists learned more and more about the composition of simple
compounds, it became important to develop a system for naming these compounds in a way
that showed their elemental composition. Common and descriptive names like salt, cinnabar,
laughing gas, and blue vitriol tell us nothing about what is in a compound. Chemical names
like sodium chloride, magnesium oxide, mercuric sulfide, nitrous oxide and cupric sulfate
do a better job of conveying information about what elements are contained in a compound. |
| Common name |
Chemical name |
Elements contained |
| salt |
sodium chloride |
Na |
Cl |
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| magnesia |
magnesium oxide |
Mg |
O |
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| cinnabar |
mercuric sulfide |
Hg |
S |
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| laughing gas |
nitrous oxide |
N |
O |
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| blue vitriol |
cupric sulfate |
Cu |
S |
O |
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Here are some simple guidelines of what to look for in chemical names. (These compounds
are also listed in Example 2 in your workbook.)
| Generally when two elements combine, the name of the compound contains the
names of both elements with the ending on the second element changed to "-ide." |
| Simple names of compounds with two elements |
| Name of compound |
Elements contained |
| sodium chloride |
sodium and chlorine |
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| When the elements can form two compounds, the ending on the
first element is changed to indicate how much of the second element it has combined with.
The "-ic" ending indicates that the first element has combined with a large
amount of the second element. The "-ous" ending indicates that the first element
has combined with a small amount of the second element. The terms "large" and
"small" are, of course, relative and they are related to the ratios in the Law
of Simple Multiple Proportions. |
| Latin endings in names of compounds |
| Name of compound |
Elements contained |
| mercuric sulfide |
mercury with more sulfur |
| mercurous sufide |
mercury with less sulfur |
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| nitric oxide |
nitrogen with more oxygen |
| nitrous oxide |
nitrogen with less oxygen |
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Sometimes you will see a Roman numeral in parentheses attached to the end of the first
element. These are Stock names and the Roman numeral tells us about the condition (charge
or oxidation state) of the element it follows. We will have to deal with that when we talk
about how atoms bond to one another later in this course. |
| Roman numerals in names of compounds |
| iron(III) oxide |
iron (in a +3 state) with oxygen |
| iron(II) oxide |
iron (in a +2 state) with oxygen |
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| When an "-ate" ending is found in a name, it indicates that
oxygen has combined with the other two elements. |
| Compound names with -ate endings |
| cupric sulfate |
copper with sulfur and oxygen |
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Sometimes names will contain prefixes. The prefix is used to indicate the relative
amounts of each element expressed in a way that I will soon discuss. For the moment, let's
just leave it at the understanding that carbon dioxide contains both carbon and oxygen. In
time you will learn which types of compounds have prefixes in their names and which do
not. |
Names containing prefixes |
| carbon dioxide |
1 carbon with 2 oxygens |
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E-mail instructor:
Eden Francis
Clackamas Community College
©1998, 2002 Clackamas Community College, Hal Bender
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