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3.7: Ionic Bonding: Writing Chemical Names of Ionic Compounds Containing Main Group Elements

  • Page ID
    214686
  • Learning Objectives
    • Write the chemical names of ionic compounds containing main group elements.

    In the previous section, the process for writing the chemical formula of an ionic compound containing main group elements was presented and applied.  The chemical name of a compound is derived based on the information included in its chemical formula.  A chemical name should uniquely correspond to a single chemical formula.  In other words, no two chemical formulas should share a common chemical name.  The procedure for writing the chemical name of an ionic compound containing main group elements is explained in the following paragraphs.

    Naming Ionic Compounds Containing Main Group Elements

    The chemical name of an ionic compound is based solely on the identities of the ions that it contains.  Specifically, the names of the ions are modified by removing the word "ion" from each, and the remaining terms are written in the order in which they appear in the corresponding ionic chemical formula.  Since the subscripts in an ionic chemical formula are the result of achieving charge-balance between the compound's constituent ions, referencing subscripts in an ionic chemical name is considered redundant.  Therefore, ionic compounds do not include any numerical prefixes.  

    For example, consider K3N, which is the chemical formula for the ionic compound that is formed when nitrogen and potassium bond with one another.

    These elements bond with one another as ions, not as neutral atoms.  Therefore, more accurately, K3N is the chemical formula for the ionic compound that is formed when the nitride ion, N–3, the anion formed upon the ionization of nitrogen, and the potassium ion, K+1, the cation formed when potassium ionizes, bond with one another.  Recall that the suffix of an anion is "-ide," as a verbal indicator of its negative charge. 

    When naming an ionic compound, the word "ion" is removed from each of these terms, as no charges are explicitly-written in an ionic chemical formula.  Each constituent particle, such as N–3 and K+1, is charged and, consequently, has a name that includes the word "ion."  However, an ionic compound, such as K3N, is a net-neutral species, due to the charge-balance achieved between these particles.  Therefore, the term "ion" should not be incorporated into the chemical name of an ionic compound.  In this example, "nitride ion" is shortened to "nitride," and "potassium ion" simply becomes "potassium."

    Finally, since the cation is symbolized before the anion in an ionic chemical formula, the cation term appears first in the chemical name of an ionic compound.  Therefore, in this example, the term "potassium" is written before "nitride."  As the subscripts in an ionic chemical formula are not referenced in an ionic chemical name, the result of combining these terms, "potassium nitride," is the chemically-correct name for K3N.

    Example \(\PageIndex{1}\)

    Write the chemical name of Al2S3, the ionic compound that is formed when aluminum and sulfur bond with one another.

    Solution

    More accurately, Al2S3 is the chemical formula for the ionic compound that is formed when the aluminum ion, Al+3, the cation formed when aluminum ionizes, and the sulfide ion, S–2, the anion formed upon the ionization of sulfur, bond with one another.  

    When naming an ionic compound, the word "ion" is removed from each of these terms, as no charges are explicitly-written in an ionic chemical formula.  As a result, "sulfide ion" is shortened to "sulfide," and "aluminum ion" simply becomes "aluminum."  Finally, since the cation is symbolized before the anion in an ionic chemical formula, the cation term appears first in the chemical name of an ionic compound.  Therefore, the term "aluminum" is written before "sulfide."  As the subscripts in an ionic chemical formula are not referenced in an ionic chemical name, the result of combining these terms, "aluminum sulfide," is the chemically-correct name for Al2S3.

    Exercise \(\PageIndex{1}\)

    Write the chemical name that corresponds to each of the following chemical formulas. 

    1. CaO, the ionic compound that is formed when calcium and oxygen bond with one another.
    2. MgCl2, the ionic compound that is formed when chlorine and magnesium bond with one another.
    Answer a
    More accurately, CaO is the chemical formula for the ionic compound that is formed when the calcium ion, Ca+2, the cation formed when calcium ionizes) and the oxide ion, O–2, the anion formed upon the ionization of oxygen, bond with one another.

    When naming an ionic compound, the word "ion" is removed from each of these terms, as no charges are explicitly-written in an ionic chemical formula.  As a result, "oxide ion" is shortened to "oxide," and "calcium ion" simply becomes "calcium."  Finally, since the cation is symbolized before the anion in an ionic chemical formula, the cation term appears first in the chemical name of an ionic compound.  Therefore, the term "calcium" is written before "oxide."  As the subscripts in an ionic chemical formula are not referenced in an ionic chemical name, the result of combining these terms, "calcium oxide," is the chemically-correct name for CaO.
    Answer b
    More accurately, MgCl2 is the chemical formula for the ionic compound that is formed when the chloride ion, Cl–1, and the magnesium ion, Mg+2, bond with one another.  The word "ion" is removed from each of these terms, as no charges are explicitly-written in an ionic chemical formula.  As a result, "chloride ion" is shortened to "chloride," and "magnesium ion" simply becomes "magnesium."  Finally, the cation term appears first in the chemical name of an ionic compound, so the term "magnesium" is written before "chloride."  As the subscripts in an ionic chemical formula are not referenced in an ionic chemical name, "magnesium chloride," is the chemically-correct name for MgCl2.