Binary ionic compound

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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"

   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.

   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.

   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

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

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