Chapter 5 · Molecules and Compounds
5.6Nomenclature: Naming Compounds
8 min · two checks
Predict
Why can’t one naming rule cover every compound?
The idea
- Decide which naming system a formula needs.
- List the three systems you will practice next.
A name is a classification decision followed by a pattern. If the formula starts with a metal or with ammonium, treat it as ionic: name the cation, then the anion. If it contains only nonmetals and is not an acid in water, treat it as molecular: use prefixes to count atoms. If it is an acid (hydrogen plus an anion, dissolved in water, or written as HCl, HNO₃, and so on in the acid sense), use the acid pattern. Applying prefixes to NaCl (“monosodium monochloride”) is a category error, not extra precision.
The next three sections drill each pattern. This section’s skill is the fork in the road. Look at the first element. Look for a polyatomic ion you recognize. Look for hydrogen at the front of an acid. Then pick the system. A flowchart you draw yourself — metal? polyatomic? hydrogen acid? otherwise molecular — will outperform a memorized paragraph.
Keep these
- Classify before you name: ionic, molecular, or acid.
- Ionic names do not use numeric prefixes.
- Molecular names of binary compounds do use prefixes.