5: Nomenclature of inorganic compounds

Nomenclature of Inorganic Compounds

Systematic naming of inorganic compounds ensures precise communication in chemistry. Mastery of naming rules is essential for interpreting formulas and reactions.

Binary Ionic Compounds

Formed between metals and nonmetals. Name the cation (metal) first, then the anion (nonmetal) with the suffix -ide.

• Fixed-charge metals (Groups 1, 2, Al, Zn, Ag, Cd): Use the element name.
  Example: $NaCl \to$ Sodium chloride.
• Variable-charge metals (transition metals, Pb, Sn): Indicate charge with Roman numerals.
  Example: $FeCl_2 \to$ Iron(II) chloride; $FeCl_3 \to$ Iron(III) chloride.

Binary Covalent Compounds

Formed between two nonmetals. Use prefixes to denote atom counts:

Prefix	Number
mono-	1
di-	2
tri-	3
tetra-	4

Example: $N_2O_4 \to$ Dinitrogen tetroxide.
Exception: Omit mono- on the first element ($CO_2 \to$ Carbon dioxide).

Acids and Oxyanions

• Oxyanions: Polyatomic ions with oxygen.
  • -ate suffix: Most common form ($SO_4^{2-} \to$ Sulfate).
  • -ite suffix: One less oxygen ($SO_3^{2-} \to$ Sulfite).
  • Prefixes hypo- (least oxygen) and per- (most oxygen):
    Example: $ClO^- \to$ Hypochlorite; $ClO_4^- \to$ Perchlorate.
• Acids:
  • -ate becomes -ic acid ($H_2SO_4 \to$ Sulfuric acid).
  • -ite becomes -ous acid ($H_2SO_3 \to$ Sulfurous acid).
  • Binary acids use hydro- and -ic acid ($HCl_{(aq)} \to$ Hydrochloric acid).

Key Polyatomic Ions

Memorize common ions:

• Cations: $NH_4^+$ (Ammonium), $H_3O^+$ (Hydronium).
• Anions: $NO_3^-$ (Nitrate), $CO_3^{2-}$ (Carbonate), $PO_4^{3-}$ (Phosphate), $OH^-$ (Hydroxide).

Hydrates

Ionic compounds with water molecules use prefixes + hydrate:
Example: $CuSO_4 \cdot 5H_2O \to$ Copper(II) sulfate pentahydrate.

Summary of Rules

1. Identify compound type (ionic/covalent/acid).
2. For ionic: Name cation, then anion (-ide or polyatomic name).
3. For covalent: Use prefixes.
4. For acids: Adjust suffix based on anion (-ic for -ate, -ous for -ite).
5. Specify metal charges when variable.