Naming Ionic Compounds

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The chemicals that you will encounter during your chemistry course(s) will undoubtedly fall into many different categories: ionic, binary molecular, acid, coordination compounds, and organic compounds. Each of these classes of compounds uses a unique naming system. In Chem I and II, you will be responsible for naming and writing formulas for commmon ionic compounds, binary molecular compounds, acids, and simple organic compounds.

Since each of these classes of compounds uses a unique naming system, the first step in correctly naming a compound is to identify the type of compound that it is. You can do this by looking at the formula for the compound.

Ionic Compounds: As a rule of thumb, ionic compounds generally consist of a metal and one or more non-metals. The main exception to this are those ionic compounds that contain the ammonium ion (NH4+). All compounds whose formulas begin with NH4+ are also ionic.

Binary Molecular Compounds: As a general rule, binary molecular compounds contain two different non-metals.

Acids: The formulas for inorganic acids (those that do not contain a C-C skeleton) will start with "H" (or H2 or H3, etc).

To name an ionic compound you simply need to find the names of the cation and anion present in the compound.

  1. Identify the cation:

  2. Identify the anion:

  3. Write the name of the ionic compound by writing the name of the cation followed by the name of the anion.

    • Use the list of ion names from your book, the syllabus, or the hand-out on my web-site to find the names of the ions. Remember, Chem I students are responsible for knowing the names and formulas of the ions listed in the syllabus. Chem II students are responsible for the names of all ions.

Example: Write the correct name for the compound whose empirical formula is Na2SO4.

  1. Na2SO4 is an ionic compound because it contains a metal (Na) and two non-metals (S and O).
  2. Identify the cation:
  3. Identify the anion:
  4. The correct name for Na2SO4 is sodium sulfate. Notice that the word "ion" is omitted from the name of the cation and anion when incorporating them into the name of the compound.

Example: Write the correct name for the compound whose empirical formula is (NH4)2CO3.

  1. Even though this compound is composed of only non-metals, it is still an ionic compound. (It starts with NH4.)
  2. Identify the cation:
  3. Identify the anion:
  4. The correct name for this compound is ammonium carbonate.

Example: Write the correct name for the compound whose empirical formula is SnO2.

  1. This compound is an ionic compound. It contains a metal (Sn) and a non-metal (O).
  2. Identify the cation:
  3. Identify the anion:
  4. The correct name for the compound is tin (IV) oxide.

Practice Problems

Name the following compounds:

  1. MgCl2
  2. KOH
  3. Ba(NO3)2
  4. NaHCO3
  5. Pb(SO4)2
  6. CuO
  7. NaClO

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