Overview
This lecture explains how to name chemical compounds by understanding the different types of chemical bonds, rules for naming covalent and ionic compounds, and the use of prefixes and Roman numerals.
Types of Chemical Bonds
- Metals and nonmetals are separated on the periodic table; metals form metallic bonds, nonmetals form covalent bonds, and metal plus nonmetal forms ionic bonds.
- Bond type can be determined by comparing electronegativity values.
Naming Covalent Compounds
- If two nonmetals combine, name the element with the lower group number first; if in the same group, use the greater period number.
- The first element keeps its name; the second is named as an anion (ending with -ide).
- Use prefixes (mono-, di-, tri-, tetra-, etc.) to indicate the number of each atom; do not use 'mono-' for the first element.
- Examples: CO₂ = carbon dioxide (not monocarbon dioxide), P₃N₄ = triphosphorus tetranitride, CH₄ = carbon tetrahydride.
Naming Ionic Compounds
- Always write the cation (positive ion) first, followed by the anion (negative ion).
- If the metal can have multiple charges (like iron or copper), specify its charge with Roman numerals in parentheses.
- For polyatomic ions (ions made of several atoms), use their established names (e.g., NO₃⁻ = nitrate, SO₃²⁻ = sulfite).
- Example: Li₂O = lithium oxide; (NH₄)₃P = ammonium phosphide.
- For compounds with metals of variable charge: Cu(NO₃)₂ = copper(II) nitrate; Ni₂(SO₃)₃ = nickel(III) sulfite.
Key Terms & Definitions
- Covalent bond — bond between two nonmetals sharing electrons.
- Ionic bond — bond between a metal and a nonmetal involving electron transfer.
- Cation — positively charged ion.
- Anion — negatively charged ion.
- Polyatomic ion — charged ion composed of two or more atoms.
- Prefixes (mono-, di-, tri-, tetra-) — indicate the number of atoms in covalent compounds.
Action Items / Next Steps
- Review your periodic table and polyatomic ions chart.
- Practice naming additional compounds for mastery.