Naming Chemical Formulas
Naming Chemical Formulas Chemical Nomenclature
There are over 19 million known chemical substances. Without some type of system, naming these substances would be hopelessly complicated. The system used in naming substances is called chemical nomenclature.
There are two major divisions to the International Union of Pure and Applied Chemistry (IUPAC) system:
inorganic nomenclature organic nomenclature
Organic compounds contain carbon, usually in combination with hydrogen, oxygen, nitrogen, and/or sulfur.
All other substances are inorganic compounds, divided into three basic categories:
ionic compounds molecular compounds acids
Naming inorganic compounds begins with naming ions.
Cations formed from metal atoms have the same name as the metal. See a chart of common cations
If - and ONLY if - a metal can form different cations, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal. Fe+2 iron (II)
Fe+3 iron (III)
The names of monatomic anions are formed by replacing the ending of the name of the element with -ide. See a chart of common anions.
Cl− chloride ion
Br− bromide ion
S−2 sulfide ion
Polyatomic ions The short list The long list
A few simple polyatomic anions also have names ending in -ide. OH− hydroxide ion
CN− cyanide ion Polyatomic cations formed from nonmetal atoms have names ending in -ium. NH4+ ammonium ion
H3O+ hydronium ion Polyatomic anions containing oxygen (oxyanions) have names ending in -ate or -ite. The ending -ate is used for the most common oxyanion of an element. NO3− nitrate ion
SO4−2 sulfate ion The ending -ite is used for an oxyanion that has the same charge but one less oxygen atom. NO2− nitrite ion
SO3−2 sulfite ion Prefixes are used when the series of oxyanions of an element extends to four members: The prefix per- indicates one more oxygen atom than the oxyanion ending in
There are over 19 million known chemical substances. Without some type of system, naming these substances would be hopelessly complicated. The system used in naming substances is called chemical nomenclature.
There are two major divisions to the International Union of Pure and Applied Chemistry (IUPAC) system:
inorganic nomenclature organic nomenclature
Organic compounds contain carbon, usually in combination with hydrogen, oxygen, nitrogen, and/or sulfur.
All other substances are inorganic compounds, divided into three basic categories:
ionic compounds molecular compounds acids
Naming inorganic compounds begins with naming ions.
Cations formed from metal atoms have the same name as the metal. See a chart of common cations
If - and ONLY if - a metal can form different cations, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal. Fe+2 iron (II)
Fe+3 iron (III)
The names of monatomic anions are formed by replacing the ending of the name of the element with -ide. See a chart of common anions.
Cl− chloride ion
Br− bromide ion
S−2 sulfide ion
Polyatomic ions The short list The long list
A few simple polyatomic anions also have names ending in -ide. OH− hydroxide ion
CN− cyanide ion Polyatomic cations formed from nonmetal atoms have names ending in -ium. NH4+ ammonium ion
H3O+ hydronium ion Polyatomic anions containing oxygen (oxyanions) have names ending in -ate or -ite. The ending -ate is used for the most common oxyanion of an element. NO3− nitrate ion
SO4−2 sulfate ion The ending -ite is used for an oxyanion that has the same charge but one less oxygen atom. NO2− nitrite ion
SO3−2 sulfite ion Prefixes are used when the series of oxyanions of an element extends to four members: The prefix per- indicates one more oxygen atom than the oxyanion ending in