Ch 5: Nomenclature
5.1 Naming Compounds
• Many compounds have common names:
Ex:
H2O = water
NH3 = ammonia
CH4 = methane
• There must be system for naming (nomenclature) the thousands of known chemical compounds.
• Compounds named in this chapter:

Binary compounds -- those composed of two elements:
•
Metal with a nonmetal (ionic)
•
Two nonmetals (nonionic)

Polyatomic compounds -- composed of a metal and a PA anion, or two PA ions.

Acids -- H+ and an anion.
5.2 Naming Compounds that Contain a Metal and aNonmetal
• Binary ionic compounds contain a metal cation and a nonmetal anion.
• Rules for naming:
 Name the metal cation first, then name the nonmetal anion.
 The metal cation name is the metal name.
 The nonmetal anion name uses the root of the element name and adding –ide suffix.
See table 5.1
 For metals that can form more than one type of cation -- such as transition metals, and
Group 4A metals -- the cation name is the metal name followed by a Roman numeral in
parentheses to indicate its charge.
 See
Table 5.2
• The net charge on an ionic compound is always zero.
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• Examples: text pg 126-127, 129
5.3 Naming Binary Compounds Containing only Nonmetals
•
These compounds do not contain ions.
•
Rules for naming:
 Name the first element in formula using the full name of the element.
 Name the second element in the formula as if it were an anion (root name plus –ide
suffix).
 Use a prefix in front of each name to indicate the number of atoms. (See Table 5.3)
 Never use the prefix mono- on the first element.
 Drop last “a” in the prefix if the name begins with vowel.
See Table 5-3 in text
Examples: see pages 132 -133
5.4 (Skip)
5.5 Naming Compounds that Contain Polyatomic Ions
• Polyatomic ions are charged entities composed of several atoms bound together.
• Must memorize name, formula and charge.

See list of PA ions given you, or Table 5.4

Oxyanions – polyatomic anions that contain a given element with different numbers of oxygen.
• Polyatomic compounds:
 are ionic compounds because they contain ions bonded together.
 are not binary compounds because they contain more than two elements.
 Contain a metal combined with a polyatomic ion or can be composed of two polyatomic ions

Examples:
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• Rules for naming:
 Name metal cations as in binary ionic compounds. (Use Roman numerals when necessary.)
 Use the name of the polyatomic ion part of the compound as written.
 Put parentheses around polyatomic ions when more than one is present.
 Examples:
5.6 Naming Acids
• Acids are compounds that produce H+ cations and an anion when dissolved in water.
• Rules for naming: see handout
5.7 Writing the Formulas from the Names
•
For binary ionic compounds (metal and a nonmetal), polyatomic compounds, and acids.
 Determine the ions present.
 Determine the charges on the cation and anion.
 Balance the charges to get the formula subscripts.
•
For binary compounds composed of two nonmetals, use the prefixes to determine the
formula subscripts.
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