Ionic Compounds Naming and Formulas

Naming Ionic Compounds

General Principles

  • Naming Convention: Metal name first, nonmetal name second (with ide ending).
  • Cation/Anion Identification: Identify cation (metal) and anion (nonmetal) before naming.

Examples of Naming

Example Compound: K2O

  1. Identify cation & anion.
    • Cation: K+ (Potassium, Group 1A)
    • Anion: O2− (Oxide, Group 6A)
  2. Name cation: potassium
  3. Name anion: oxide
  4. Final name: potassium oxide.

Additional Examples:

  • A. CaO: Calcium oxide
  • B. Al2S3: Aluminum sulfide
  • C. MgCl2: Magnesium chloride

Variable Charge Metals

  • Transition metals may have multiple charges; indicated by Roman numerals in name.
    • Example: Fe2+ is iron(II), Fe3+ is iron(III).
    • Example Compound: FeCl2
    1. Determining cation from anion charge.
    2. Name: iron(II) chloride.

Example for MnO2:

  • Step 1: Determine charge from O2−. Mn must be 4+ (manganese(IV) oxide).

Writing Formulas from Names

  • Procedure: From the ionic compound name, identify the metal and nonmetal and derive their symbols, balancing the charges.
  • Example: Tin(II) chloride: Sn2+ and Cl− lead to formula SnCl2.

Learning Checks

  • Write names/formulas for given ions and history of ionic compounds.
  • Questions on naming and writing formulas, e.g., nickel(II) sulfide as NiS.

Summary of Charges & Balancing

  • Balance cation and anion charges in forming compounds.
  • Charge balance provides subscripts for final formulas: e.g., ZnCl2 from Zn2+ and Cl−.