Binary ionic compound

A binary ionic compound is a salt consisting of only two elements in which both elements are ions, a cation and an anion. When naming these compounds, its composition must be considered. Type 1 binary ionic compounds are those in which the cation has only one form, or charge. Type 2 binary ionic compounds are those in which the cation can have multiple forms. Additionally, binary ionic compounds containing polyatomic ions have another distinct set of naming rules.

Naming Type I Binary Ionic compounds (metal and nonmetal):

The metals used have to be from Group 1, 2, or Al³⁺, Zn²⁺, Ag⁺.

1. The cation (which is a metal in most cases) is listed first and the anion (which is a nonmetal in most cases) second

2. The cation takes the name of its elemental form. For example, Li+ would be called "Lithium".

3. The anion name uses the first part of its elemental name, and subsequently adding the suffix "-ide". For example, Br^- would be called "Bromide"

   Examples:
   LiF (which is composed of Li+ cation and F− anion) = lithium fluoride
   BaO (which is composed of Ba2+ cation and O2- anion) = barium oxide

Naming Type II Binary Ionic compounds (metal and nonmetal):

Metals used are transition metals except for Al³⁺, Zn²⁺, Ag⁺.

1. The steps follow those of Type 1 Binary Ionic compounds however, since the cation can take on multiple charges, the charge must be written within parentheses in Roman numerals after stating the cation name.

   Examples:
   CoO (which is composed of Co²+ cation and O²- anion) = cobalt(II) oxide
   FeN (which is composed of Fe³+ cation and N³- anion) = iron(III) nitride

Note that there is another way to name Type 2 ionic compounds that is not as common. This involves using an alternate, Latin name for the cation. Common Type 2 cation include Iron, Copper, Cobalt, Tin, Lead, and Mercury.

Naming Binary Compounds with Polyatomic Ions:

1. The cation is listed first and the anion second.

2. The polyatomic ion names must be memorized.

3. No extra suffixes are added.

   Examples:
   NaCN (which is composed of Na+ cation and CN- polyatomic anion) = sodium cyanide
   NH4Cl (which is composed of NH4+ polyatomic cation and Cl- anion) = ammonium chloride

See also

Binary compound

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References: Zumdahl, Steven S. Chemical Principles, Fifth Edition. New York: Houghton Mifflin, 2005. 34-39.