Overview
This lesson covers chemical nomenclature, comparing IUPAC and traditional naming, writing and reading chemical formulas, oxidation numbers, the classification of compounds, and naming binary, ternary, and quaternary salts.
Chemical Nomenclature Systems
- Chemical nomenclature assigns systematic names to compounds for clear identification.
- IUPAC nomenclature is an international system, created in 1919, that describes chemical composition in the compound’s name.
- Traditional nomenclature uses historical or common names, which may not reveal composition (e.g., ammonia, carbon dioxide).
Writing and Reading Chemical Formulas
- Early chemists used symbols for elements and compounds, assigning each known substance a symbol.
- Modern formulas reflect the ratios (stoichiometry) of atoms in molecules.
- Indices specify the number of atoms per element to achieve a neutral molecule.
Oxidation Numbers
- Oxidation numbers represent the formal charge of an atom in a compound.
- The sum of oxidation numbers in a neutral molecule is zero; in ions, it equals the ionic charge.
- Hydrogen usually has +1 or -1, oxygen usually -2, with exceptions for peroxides and superoxides.
- Elements in their elemental state have oxidation number zero.
Classification and Types of Compounds
- Inorganic compounds include binary (2 elements), ternary (3 elements), and quaternary (4 elements) compounds.
- Oxides: oxygen compounds with metals (basic oxides) or non-metals (acidic/anhydrides).
- Hydrides: hydrogen combined with metals or non-metals.
- Salts: formed from a metal and a non-metal, can be binary, ternary, or quaternary.
Nomenclature Rules for Binary and Ternary Compounds
- IUPAC: names reflect composition and oxidation state, using prefixes (mono-, di-, tri-) and suffixes.
- Traditional: uses suffixes (-ous for lower and -ic for higher oxidation states, masculine/feminine as needed).
- Stock system: uses Roman numerals to indicate oxidation state.
Common Examples and Exercises
- Aluminum oxide (Al₂O₃): trioxide of aluminum (IUPAC), aluminum oxide (traditional).
- Iron oxides: FeO (iron(II) oxide, ferrous oxide), Fe₂O₃ (iron(III) oxide, ferric oxide).
- Sulfur oxides: SO₂ (sulfurous, lower oxidation), SO₃ (sulfuric, higher oxidation).
Ions and Polyatomic Ions
- Cations (positive) and anions (negative) form ionic compounds.
- Polyatomic ions (e.g., SO₄²⁻ sulfate, NO₃⁻ nitrate) are named with suffixes -ate for higher, -ite for lower oxidation states.
- Prefixes hypo- and per- indicate extremes in oxidation numbers.
Hydroxides and Oxoacids
- Hydroxides: ternary compounds of metal, oxygen, and hydrogen (e.g., NaOH, calcium hydroxide).
- Oxoacids: non-metal, oxygen, and hydrogen, formed by adding water to non-metal oxides.
Salts: Binary, Ternary, Quaternary
- Binary salts: metal + non-metal (e.g., NaCl, MgCl₂).
- Ternary salts: metal + non-metal + oxygen (e.g., CaCO₃, NaNO₃).
- Quaternary salts: metal + hydrogen + non-metal + oxygen (e.g., NaHSO₄, NaHCO₃).
Key Terms & Definitions
- IUPAC nomenclature — International method for systematic chemical naming.
- Oxidation number — Formal charge assigned to an atom in a compound.
- Binary compound — Compound with two different elements.
- Ternary compound — Compound with three different elements.
- Quaternary compound — Compound with four different elements.
- Hydroxide — Compound containing OH⁻ group.
- Oxoacid — Acid containing oxygen, hydrogen, and a non-metal.
- Stock system — Roman numeral notation for oxidation state.
- Peroxide — Compound with oxygen at -1 oxidation state.
- Superoxide — Compound with oxygen at -½ oxidation state.
Action Items / Next Steps
- Practice writing chemical formulas and names using both IUPAC and traditional nomenclature.
- Review the tables of prefixes, suffixes, and oxidation numbers.
- Complete exercises on naming oxides, hydrides, hydroxides, acids, and salts.
- Prepare for the next lesson on chemical reactions.