Nomenclature & Ionic/Covalent Compounds - Quick Reference

IONIC COMPOUND

• Crystalline solids formed by oppositely charged ions; usually from metals reacting with nonmetals.
• Ions form to achieve a noble gas configuration (octet) via electron gain/loss.
• Giant ionic lattice held by strong electrostatic forces; high melting and boiling points; brittle.
• Conductivity: good conductors when molten or in aqueous solution due to mobile ions.
• Common example: sodium chloride, NaCl, dissociates in water to Na⁺ and Cl⁻ (ions are free to move). $ext{Na^+}, ext{Cl^-}$

MONOTOMIC CATIONS NAMING (Rule 1)

• Monatomic cation name = element name + ion. E.g., sodium ion = $ext{Na^+}$ ion.
• Different elements form different charges; some elements form more than one cation.
• Iron can form two cations: $ext{Fe^{2+}}$ and $ext{Fe^{3+}}$.
• Stock vs classical nomenclature:
  • Iron(II) ion = $ext{Fe^{2+}}$; Ferrous (classical) name.
  • Iron(III) ion = $ext{Fe^{3+}}$; Ferric (classical) name.

BINARY IONIC COMPOUNDS (METAL + NONMETAL) NAMING (Rule 2)

• Binary ionic compound = two different elements (one metal, one nonmetal).
• Name order: cation name (with charge if necessary) + anion name (stem + -ide).
• Examples:
  • $ext{CaCl_2}$ → Calcium chloride.
  • $ext{KF}$ → Potassium fluoride.

IONIC COMPOUNDS WITH POLYATOMIC IONS (Rule 3)

• Naming follows the same rule: cation name + polyatomic anion name.
• Example: $ext{CaCO<em>3}$ → Calcium carbonate (carbonate is the polyatomic anion, $ext{CO</em>3^{2-}}$).

COVALENT COMPOUND NAMING (Rule 4)

• Covalent bonds form when two or more nonmetals share electrons.
• Naming: first element named as is; second element uses stem + -ide; prefixes indicate the number of atoms.
• No prefix for 1 atom.
• Examples:
  • ext{PCl_4}
    ightarrow ext{Phosphorus tetrachloride}.
  • ext{C3H8}
    ightarrow ext{Tricarbon octahydride} ext{ (propane)}.

ACIDS NAMING (RULES 5–7)

• General: an acid is a molecular compound with one or more H atoms that produces $H^+$ in water.
• Acids containing -ide anions:
  • Use prefix hydro- and change -ide to -ic, then add acid.
  • Example: $ext{HCl}$ → Hydrochloric acid; anion Cl⁻ (chloride).
  • Example: $ext{HCN}$ → Hydrocyanic acid; anion CN⁻ (cyanide).
• Acids containing -ate anions:
  • Change -ate to -ic, then add acid.
  • Example: $ext{SO<em>4^{2-}}$ → Sulfuric acid; acid formula $ext{H</em>2SO_4}$.
• Acids containing -ite anions:
  • Change -ite to -ous, then add acid.
  • Example: $ext{SO<em>3^{2-}}$ → Sulfurous acid; acid formula $ext{H</em>2SO_3}$.

ADDITIONAL KEY POINTS

• Ionic compounds typically have high mp/bp due to strong lattice bonds.
• Covalent compounds typically have lower mp/bp and are often liquids/gases at room temperature; poorer electrical conductors in all states.
• For ionic compounds, the total positive charge must balance the total negative charge (net zero).
• In aqueous solutions, many ionic compounds dissociate into mobile ions, enabling conductivity.