2.8 | Naming Inorganic compounds

Chemical Nomenclature

• Definition: The system of naming substances in chemistry; derived from Latin words nomen (name) and cala (to call).

• Importance: Understanding names and formulas of compounds is key in chemistry. There are over 50 million known compounds, making unique naming essential.

Classification of Compounds

• Organic Compounds:

  • Contain carbon and hydrogen.

  • Often combined with oxygen, nitrogen, or other elements.

  • Historically associated with living organisms.

• Inorganic Compounds:

  • Any compound that is not organic, including minerals and water.

  • Useful classification, though the distinction from organic is less relevant today.

Basic Rules for Naming Inorganic Compounds

Categories

1. Ionic Compounds

2. Acids

3. Molecular Compounds

Naming Ionic Compounds

• Structure: Composed of cations (positive) and anions (negative).

• Cation Naming:

  • Names the same as the metal, e.g.,

    • Na⁺ → Sodium ion

    • Zn²⁺ → Zinc ion

    • Al³⁺ → Aluminum ion

  • Variable Charge Metals: Use Roman numerals to indicate charge.

    • Fe²⁺ → Iron (II)

    • Fe³⁺ → Iron (III)

    • Cu²⁺ → Copper (II)

• Common Metals with Fixed Charges:

  • Group 1 and Group 2 metals, Al³⁺, Ag⁺, and Zn²⁺.

• Polyatomic Cations: Names end in "ion".

  • Examples: NH₄⁺ (Ammonium ion), H₃O⁺ (Hydronium ion).

Naming Anions

1. Monatomic Anions: Replace element name ending with -ide.

   • Examples: H⁻ → Hydride, O²⁻ → Oxide, N³⁻ → Nitride.

2. Polyatomic Anions (Oxyanions):

   • Names ending in -ate (higher oxygen) and -ite (lower oxygen).

   • Examples: NO₃⁻ (Nitrate), SO₄²⁻ (Sulfate) vs. NO₂⁻ (Nitrite), SO₃²⁻ (Sulfite).

   • Prefixes indicate number of oxygen atoms:

     • Per- (one more), Hypo- (one less).

Naming Formulas of Ionic Compounds

• Structure: Cation name + Anion name.

  • Examples:

    • CaCl₂ → Calcium chloride

    • Al(NO₃)₃ → Aluminum nitrate

    • Cu(ClO₄)₂ → Copper (II) perchlorate

Naming Acids

• Definition: Substances releasing H⁺ in water.

• Naming Convention:

  • Anions ending in -ide become acids and end with -ic, adding "hydro-" before acid.

  • Examples:

    • Cl⁻ → HCl (Hydrochloric acid).

  • For Oxyanions:

    • -ate becomes -ic, -ite becomes -ous.

    • Examples:

      • ClO₄⁻ → HClO₄ (Perchloric acid)

      • ClO₃⁻ → HClO₃ (Chloric acid)

      • ClO₂⁻ → HClO₂ (Chlorous acid)

      • ClO⁻ → HClO (Hypochlorous acid)

Naming Binary Molecular Compounds

Rules

1. Element further left in the periodic table is named first (with exceptions).

2. If in the same group, the element lower in the table is named first.

3. The second element receives an -ide ending.

4. Greek prefixes indicate number of atoms (except mono with first element).

   • Examples:

     • CO₂ → Carbon dioxide

     • N₂O₄ → Dinitrogen tetroxide

     • P₄S₁₀ → Tetraphosphorus decasulfide.