Overview
This lecture covers the rules and strategies for naming and writing formulas of ionic and covalent (molecular) compounds, including cases with transition metals and polyatomic ions.
Identifying Compound Types
- Ionic compounds consist of a metal and a nonmetal.
- Covalent (molecular) compounds consist of two nonmetals.
- Identifying the type of compound is the first step in naming.
Naming Ionic Compounds
- For ionic compounds without transition metals: name the metal, then the nonmetal ending in "ide."
- Charges must be balanced using subscripts in the formula.
- For ionic compounds with transition metals: name the transition metal, add its charge in Roman numerals in parentheses, then the nonmetal ending in "ide."
- The Roman numeral indicates the transition metal's charge, which can vary.
- Polyatomic ions (groups of atoms with a charge) must be memorized.
- Naming ionic compounds with a polyatomic ion: name the metal, then the polyatomic ion (usually ending in "ate" or "ite").
- If both a transition metal and a polyatomic ion are present: name the transition metal, Roman numeral for the charge, then the polyatomic ion.
Writing Names from Formulas (Ionic)
- Identify each element or polyatomic ion.
- Determine if the metal is a transition metal and use Roman numerals accordingly.
- To find the charge of transition metals, use the subscripts and known charges of other elements or ions in the formula.
Naming Covalent (Molecular) Compounds
- Covalent compounds use prefixes to indicate the number of each nonmetal atom (1 to 10).
- The first nonmetal uses a prefix (except "mono-"), the second nonmetal uses a prefix and ends in "ide."
- No charge balancing is needed for covalent compounds.
Key Terms & Definitions
- Ionic Compound — compound formed from a metal and a nonmetal; involves charge balancing.
- Covalent (Molecular) Compound — compound formed from two nonmetals; uses prefixes for atom counts.
- Transition Metal — metals in the center of the periodic table that often have multiple possible charges.
- Polyatomic Ion — a charged group of two or more covalently bonded atoms.
- Roman Numeral — indicates the charge of a transition metal in a compound name.
- Prefix — word part indicating the number of atoms (e.g., di- for 2, tri- for 3).
Action Items / Next Steps
- Memorize common ion charges, transition metal charges, and polyatomic ions.
- Learn prefixes for 1–10 for naming covalent compounds.
- Practice writing names and formulas for both ionic and molecular compounds.