Overview
This lecture explains systematic rules for naming inorganic compounds, including ionic, molecular, and acid compounds, focusing on IUPAC nomenclature guidelines.
General Principles of Nomenclature
- Nomenclature provides systematic rules for naming chemical compounds.
- Naming depends on compound type: ionic, molecular, or acid.
- Inorganic compounds focus on elements other than carbon.
Naming Ionic Compounds
- Ionic compounds are identified by whether the metal forms a fixed or variable charge ion, and if they contain polyatomic ions.
- Binary ionic compounds (two elements) are named as: cation (metal) + anion (nonmetal ending changed to -ide).
- Compounds with polyatomic ions are named by stating the cation followed by the polyatomic anion name.
- Real-world examples: NaCl (sodium chloride), NaHCO₃ (sodium bicarbonate).
Compounds With Variable Charge Metal Ions
- Metals with multiple possible charges use Roman numerals to indicate ion charge, e.g., FeCl₂ is iron(II) chloride.
- Outdated suffixes "ic" (higher charge) and "ous" (lower charge) are still sometimes used (e.g., ferrous chloride).
Ionic Hydrates
- Ionic hydrates contain water molecules; named by adding a prefix indicating water number before “hydrate” (e.g., copper(II) sulfate pentahydrate).
- Prefix examples: mono-, di-, tri-, tetra-, penta-, hexa-, etc.
- Formula uses a dot to separate compound and water (e.g., CuSO₄·5H₂O).
Naming Molecular (Covalent) Compounds
- Molecular compounds (two nonmetals) use prefixes for element numbers (e.g., CO₂ is carbon dioxide).
- Name order: more metallic (left-lower on periodic table) element first, less metallic second with -ide ending.
- Prefix "mono-" is usually omitted on the first element.
Naming Acids
- Binary acids (hydrogen + one nonmetal): “hydro-” prefix, nonmetal with “-ic” ending, and “acid.”
- Example: HCl(aq) = hydrochloric acid.
- Oxyacids (contain hydrogen, oxygen, and a third element):
- Drop "hydrogen," use root of the anion, replace "-ate" with "-ic" or "-ite" with "-ous," add “acid.”
- Example: H₂SO₄ (sulfate) = sulfuric acid.
Key Terms & Definitions
- Cation — positively charged ion (typically a metal in ionic compounds).
- Anion — negatively charged ion (typically a nonmetal or polyatomic group).
- Polyatomic ion — ion composed of several atoms bonded together.
- Hydrate — ionic compound containing water molecules within its structure.
- Binary compound — chemical compound with only two different elements.
- Molecular (covalent) compound — compound where atoms share electrons (usually nonmetals).
- Binary acid — acid composed of hydrogen and one other nonmetal.
- Oxyacid — acid containing hydrogen, oxygen, and another element.
Action Items / Next Steps
- Practice naming and writing formulas for ionic, polyatomic, and molecular compounds.
- Complete assigned textbook readings on nomenclature.
- Use online tools to reinforce learning of chemical nomenclature.