Chapter 4, Section 3: Chemical Nomenclature

Molecular Compounds

• Naming Molecular Compounds:

  • Different than ionic compounds due to lack of cations and anions.
  • Use the element further to the left or bottom of the periodic table (more metallic) first.
  • Employ Greek prefixes for ratios.
  • Drop the "mono" prefix if the first element is singular.
  • Use the "-ide" suffix for the second element.

• Greek Prefix Reference:

  • Mono-, Di-, Tri-, Tetra-, Penta-, Hexa-, Hepta-, Octa-, Nona-, Deca-

Examples:

1. Carbon Dioxide (CO₂)

   • Carbon first (left side of periodic table).
   • No prefix for one carbon; "di" prefix for two oxygens.

2. Dinitrogen Tetroxide (N₂O₄)

   • Nitrogen first (left side of periodic table).
   • "Di" for two nitrogens; "tetraoxide" for four oxygens, vowel adjustment to "tetroxide".

3. Phosphorus Pentafluoride (PF₅)

   • Phosphorus first (left and bottom of periodic table).
   • Drop "mono" for one phosphorus; "penta" for five fluorines.

Special Types of Molecular Compounds: Acids

Binary Acids

• Contain hydrogen and one other element.
• Named as hydrogen compounds in gaseous state (e.g., hydrogen bromide).
• When dissolved in water (acidic), use "hydro-" prefix and "-ic" suffix.

Examples:

1. Hydrobromic Acid (HBr)

   • "Hydro" prefix for hydrogen.
   • "Bromic" from bromine, add "acid".

2. Hydrochloric Acid (HCl)

   • "Hydro" prefix for hydrogen.
   • "Chloric" from chlorine, add "acid".

Oxyacids

• Contain hydrogen, oxygen, and one other element, often with a polyatomic ion.
• Omit hydrogen, start with the anion.
• Change "-ate" endings to "-ic".

Examples:

1. Acetic Acid (HC₂H₃O₂)

   • Anion acetate (C₂H₃O₂⁻).
   • Change "acetate" to "acetic".

2. Nitric Acid (HNO₃)

   • Anion nitrate (NO₃⁻).
   • Change "nitrate" to "nitric".

3. Nitrous Acid (HNO₂)

   • Anion nitrite (NO₂⁻), one less oxygen than nitrate.
   • Change "nitrite" to "nitrous".

4. Sulfuric Acid (H₂SO₄)

   • Anion sulfate (SO₄²⁻), adjusted for charge balance with two hydrogens.
   • Change "sulfate" to "sulfuric" (use full name of element).

Additional Notes:

• Further details on naming conventions for polyatomic ions can be found in the textbook, Chapter 4.3.
• Suggested reading for comprehensive understanding of polyatomic ion naming.