Inorganic Nomenclature: Naming Ionic and Molecular Compounds

Inorganic Nomenclature

Introduction to Chemical Nomenclature

Chemical nomenclature is the systematic method of naming chemical compounds. Accurate naming is essential for clear communication in chemistry, especially when dealing with ionic and molecular compounds. The International Union of Pure and Applied Chemistry (IUPAC) provides standardized rules for naming compounds.

• Nomenclature refers to the set of rules for naming chemical substances.

• Names convey the composition and sometimes the structure of a compound.

• Common categories include ionic compounds, molecular (covalent) compounds, and acids.

Ionic Compounds

Binary Ionic Compounds

Binary ionic compounds consist of a metal cation and a nonmetal anion. The name is constructed by stating the cation first, followed by the anion with its ending changed to -ide.

• Cation (metal) name is unchanged.

• Anion (nonmetal) name ends with -ide.

• For transition metals, the cation's charge is indicated with Roman numerals in parentheses.

Examples:

• NaCl: Sodium chloride

• FeCl3: Iron(III) chloride

• Al2O3: Aluminum oxide

Polyatomic Ions in Ionic Compounds

Many ionic compounds contain polyatomic ions—charged groups of covalently bonded atoms. The names of these ions are used directly in the compound's name.

• Common polyatomic ions include sulfate (SO42−), nitrate (NO3−), hydroxide (OH−), and acetate (C2H3O2−).

• When more than one polyatomic ion is needed, parentheses are used around the ion before adding the subscript.

Examples:

• KClO: Potassium hypochlorite

• Fe2(C2O4)3: Iron(III) oxalate

• Ba(OH)2: Barium hydroxide

• Na2SO4: Sodium sulfate

• Mg(OH)2: Magnesium hydroxide

• Al2(SO4)3: Aluminum sulfate

• Rb2SO4: Rubidium sulfate

Common Polyatomic Ions Table

Ion Name	Formula
Sulfate	SO42−
Nitrate	NO3−
Hydroxide	OH−
Acetate	C2H3O2−
Oxalate	C2O42−
Bisulfite	HSO3−
Thiocyanate	SCN−
Phosphate	PO43−
Hypochlorite	ClO−
Chromate	CrO42−
Additional info: Table entries inferred from context and standard polyatomic ions.

Molecular (Covalent) Compounds

Naming Binary Molecular Compounds

Binary molecular compounds are composed of two nonmetals. Prefixes are used to indicate the number of each atom present.

• Prefixes: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-

• The first element keeps its name; the second element ends with -ide.

• The prefix 'mono-' is usually omitted for the first element.

Examples:

• CO: Carbon monoxide

• CO2: Carbon dioxide

• N2O5: Dinitrogen pentoxide

Acids

Naming Acids

Acids are named based on the anion they contain. If the anion ends in -ide, the acid name begins with hydro- and ends with -ic acid. If the anion ends in -ate, the acid name ends with -ic acid; if it ends in -ite, the acid name ends with -ous acid.

• HCl: Hydrochloric acid

• H2SO4: Sulfuric acid

• HNO2: Nitrous acid

Practice: Naming and Formula Writing

Examples from Provided Notes

• KClO: Potassium hypochlorite

• Fe2(C2O4)3: Iron(III) oxalate

• Ba(OH)2: Barium hydroxide

• Al2(SO4)3: Aluminum sulfate

• Mg(OH)2: Magnesium hydroxide

• Rb2SO4: Rubidium sulfate

• Ni: Nickel (elemental form)

• N2O7: Dinitrogen heptaoxide

• Br2: Bromine (diatomic element)

• Na2S2O3: Sodium thiosulfate

• CH3COOK: Potassium acetate

• Additional info: Some names and formulas inferred from context and standard nomenclature rules.

Summary Table: Sample Compounds and Their Names

Formula	Name
KClO	Potassium hypochlorite
Fe2(C2O4)3	Iron(III) oxalate
Ba(OH)2	Barium hydroxide
Al2(SO4)3	Aluminum sulfate
Mg(OH)2	Magnesium hydroxide
Rb2SO4	Rubidium sulfate
N2O7	Dinitrogen heptaoxide
Na2S2O3	Sodium thiosulfate
CH3COOK	Potassium acetate
Br2	Bromine (elemental)
Additional info: Table reconstructed from fragmented notes and standard nomenclature.

Key Equations and Concepts

• General formula for ionic compounds: $\text{Cation}^{n+} + \text{Anion}^{m-} \rightarrow \text{Compound}$

• General formula for binary molecular compounds: $\text{Prefix} + \text{Element}_1 + \text{Prefix} + \text{Element}_2 + \text{-ide}$

Conclusion

Mastering chemical nomenclature is fundamental for success in general chemistry. Practice by writing names and formulas for a variety of compounds, and refer to tables of common ions and prefixes as needed.