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Naming Binary Compounds

While there are 118 chemical elements, there many combinations of the elements which make a compound. For our purposes here, a compound is made up of two or more elements. A binary compound is made up of exactly two different elements. This topic introduces the rules in naming a binary compound – that is, naming a compound with exactly two elements.

Early scientists used common names to describe certain elements and compounds. An easy example of this is salt. The expression “salt” in everyday language refers to table salt used to preserve and flavor food. The word salt has been used for many hundreds of years – long before chemistry become a sophisticated science. To chemists, the expression “salt” means something very different than singular meaning of table salt. There are many different salts that are not table salt.

Table salt is sodium chloride (NaCl), a binary compound. Magnesium chloride (MgCl2) is also binary compound and a type of salt. While epsom salt (MgSO4-7H2O) is not a binary compound, it too is a type of salt. There are so many combinations of the elements that it would be impractical (impossible, really) to memorize a simplistic and unique name of every one of the millions of combinations of elements. So instead, there is an agreed upon naming method. You can think of it as a set of rules for naming compounds. In this topic, students become familiar with the rules to name compounds with exactly two different elements.

Lesson 1 (or “Day 1”) Material
Lesson 2 (or “Day 2”) Material
Lesson 3 (or “Day 3”) Material
Lesson 4 (or “Day 4”) Material


5:48 Formulas Lesson 2: Naming Binary Ionic Compounds

9:33 Formulas Lesson 1: Writing Formulas For Binary Ionic Compounds

8:21 How to Remember Some Common Polyatomics

Compare Contrast and Debate

Kick-Off Debate Background: Polyatomic ions are named somewhat consistently most of the time. One common examples, however, does NOT follow the standard naming rules. In particular, Hydroxide (an anion with chemical formula OH) seems to follow a different naming standard. Hydrogen Oxate might be a good name for the ion – which is more closely similar to the standardized name of the hydrogen phosphate ion  (HPO4 2-).

  • Position A: All of the historically used chemical names should remain in-tact. Even if inconsistently used, the cost/effort to change them would greatly exceed any benefit derived from simplification or standardization.
  • Position B: Migrating to pure/standardized names would provide more people with an opportunity to understand important chemical processes and concepts. With the number of “exceptions to the rules” – many people get turned-off from chemistry as believing it too difficult to understand.

Resources Documents and Links

Notes and Notices

Instructor Emphasis:

  • Science & Engineering Practice: Develop and use models.
  • Cross-Cutting Concept: Systems and System Models.