Chapter 5 · Molecules and Compounds
5.10Nomenclature Summary
9 min · two checks
Predict
You see the formula SCl₂. Which naming system, and what name?
The idea
- Route any binary formula to the correct name.
- Catch the common category mistakes.
Use a short decision path. If the compound is an acid in the hydrogen-anion sense, use the acid rules from the previous section. Otherwise, if it contains a metal or ammonium, it is ionic: name the ions, add a roman numeral when the metal’s charge is not fixed, and do not use prefixes. Otherwise it is molecular: prefixes, and -ide on the second element.
The errors that lose points are predictable. Prefixes on CaCl₂. A missing roman numeral on CuCl₂. A roman numeral on NaCl. Parentheses forgotten in Mg(NO₃)₂. Hydro- stuck on an oxyacid. -ic and -ous swapped. When you practice, say the category out loud before the name. Speed comes after the fork is automatic.
Keep these
- Acid, else ionic, else molecular.
- Roman numerals report charge. Prefixes report atom counts.
- Category mistakes are the main naming errors.