Nomenclature Chapter 5 1

5.1 Naming Compounds Many compounds have common names: Ex: H2O = water NH3 = ammonia CH4 = methane To avoid confusion, there must be system for naming (nomenclature) the thousands of known chemical compounds. Compounds named in this chapter: Binary compounds -- those composed of two different elements. Three kinds: Metal (one type of cation) with a nonmetal. Bond is ionic. Metal (more than one type of cation) with a nonmetal. Bond is ionic. Two nonmetals. Bond is non-ionic. Polyatomic compounds -- composed of a metal and a PA anion, or two PA ions. Acids -- H+ and an anion. 3

5.2 Naming Compounds that Contain a Metal and a Nonmetal 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

The net charge on an ionic compound is always zero. 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. 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. If oxygen is the second element, drop the last “a” or “o” in the prefix, but never not drop “i” from a prefix. 10

Examples: see pages 132 -133 Table 5-3 Subscript Prefix 1 mono- (not with first element) 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca-

5.4 (Use my flowchart. Ignore Type I, II, III labels in the text). 5.5 Naming Compounds that Contain Polyatomic Ions Polyatomic ions are charged entities composed of several atoms bound together. 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: 12

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 15

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. 16