Naming Molecular Compounds: Ionic Compounds

Introduction to Naming Compounds

• Many substances have common names that don't reveal their chemical composition.
• The International Union of Pure and Applied Chemistry (IUPAC) sets the standard naming conventions.

Ionic Bonds and Naming

• Ionic Bonds: Formed when one atom gives an electron and another takes it.
  • Example: Sodium (Na) gives an electron to Chlorine (Cl) resulting in Na+ and Cl-.
• Naming Ionic Compounds:
  • Name the cation (metal) first, then the anion (nonmetal).
  • Change the anion's ending to "-ide".
  • Example: KCl is Potassium Chloride.

Examples of Ionic Compound Naming

• Calcium and Iodine: Calcium Iodide.
• Sodium and Nitrogen: Sodium Nitride.
• Potassium and Nitrogen: Potassium Nitride.

Writing Formulas from Names

• Sodium Chloride: NaCl (1:1 ratio).
• Barium Fluoride: BaF2 (1:2 ratio to balance charges).
• Aluminum Chloride: AlCl3 (1:3 ratio for charge balance).

Multivalent Metals

• Iron: Can be Fe2+ or Fe3+.
  • Notation example: Iron(II) or Iron(III).
  • Example: Iron(III) Chloride (FeCl3).

Determining Oxidation States

• Lead Oxide: PbO
  • Lead can be Pb2+ or Pb4+.
  • Use the charge of oxygen to determine lead’s oxidation state.

Polyatomic Ions

• Group of nonmetals acting as a unit.
  • Example: Hydroxide (OH-).
• Recognized by endings "-ate" or "-ite".

Examples

• Barium Hydroxide: Ba(OH)2 (need two OH- for each Ba2+).
• Iron(III) Carbonate: Fe2(CO3)3 (requires balancing charges to find ratio).
• Copper(II) Fluoride: CuF2 (balance charge of Cu2+ with two F-).

Special Cases with Polyatomic Ions

• Ammonium Phosphate: (NH4)3PO4
  • Ammonium is NH4+ and Phosphate is PO4 3-.
• Potassium Dichromate: K2Cr2O7 (balance K+ with dichromate's 2- charge).

Conclusion

• Use IUPAC rules and the periodic table to determine names and formulas.
• Use Roman numerals to indicate the charge of transition metals with multiple stable ions.
• Polyatomic ions require special notation and their full names as per reference charts.