Lecture on Formulas and Names of Ionic Compounds

Understanding Ionic Compounds

• Binary Ionic Compounds: Consist of two elements, typically a metal and a nonmetal.
• Polyatomic Ions: Groups of covalently bound atoms that have gained or lost electrons, forming cations or anions.
• Hydrates: Inorganic salts that incorporate water molecules into their structure in a defined ratio during crystallization.

Naming Binary Ionic Compounds

Type 1 Compounds

• Cations with single charge:

  • Typically main group metals (Groups 1A, 2A, 3A).
  • Metals lose electrons to achieve noble gas configuration.
  • Naming: metal name + "ion" (e.g., Lithium ion, Sodium ion).

• Anions:

  • Derived by dropping element’s name ending and adding "ide" (e.g., Fluoride from Fluorine, Oxide from Oxygen).
  • Combine cation and anion names to form the compound name (e.g., Lithium Fluoride).

Type 2 Compounds

• Transition Metals: Can have multiple charges.

  • Use Roman numerals in parentheses to indicate charge (e.g., Iron(III) ion).
  • Naming similar to Type 1 but include metal charge.

• Example:

  • FeCl2: Iron(II) Chloride,
  • FeCl3: Iron(III) Chloride.

Naming Polyatomic Ions

• Definition: Atoms covalently bonded, carrying a charge.
• Remembering Polyatomic Ions: Some require memorization, such as:
  • Cations: Hydronium (H3O+), Ammonium (NH4+).
  • Anions: Cyanide (CN-), Hydroxide (OH-), Carbonate (CO3^2-).
• Tricks for Oxyanions:
  • "-ate" is the parent compound (more common form).
  • "-ite" indicates one less oxygen.
  • Prefix "hypo-" and "per-" adjust for more or fewer oxygens.

Naming Hydrates

• Hydrates: Contain water molecules in a defined ratio.
• Naming: Name ionic portion first, then indicate water using prefixes (e.g., Mono-, Di-, Tri-, Tetra-...) followed by "hydrate".
  • E.g., Calcium Chloride Dihydrate (CaCl2·2H2O).

Sample Problems

Formula to Name

• MgBr2: Magnesium Bromide
• V3N5: Vanadium(V) Nitride
• Mn(C2H3O2)3: Manganese(III) Acetate
• CoF2·4H2O: Cobalt(II) Fluoride Tetrahydrate

Name to Formula

• Rubidium Sulfide: Rb2S
• Lead(IV) Oxide: PbO2
• Ammonium Phosphite: (NH4)3PO3
• Copper(I) Sulfite Monohydrate: Cu2SO3·H2O

Key Takeaways

• Mastery: Be able to both name compounds from formulas and derive formulas from names.
• Practice: Use periodic table and charge balancing to assist in understanding and memorization.

These notes summarize key elements and methodologies for naming ionic compounds, including hydrates and compounds involving transition metals or polyatomic ions. They provide a foundational understanding for studying chemistry and writing chemical formulas.