Naming Ionic Compounds

Chemical Nomenclature is the systematic naming of chemical compounds. Here we examine just a few rules for chemical substances that can be named relatively easily.

  1. Name the cation (the more electropositive one) first and the anion (the more electronegative one) second.
  2. Monoatomic cations take their name from the element name.
  3. Monoatomic anions take their names from the first part of the element name and then add "-ide".

    H+ Hydrogen
    Na+ Sodium

    What are the names for NaCl, MgO, and HBr?

    NaCl = sodium chloride

    MgO = magnesium oxide

    HBr = hydrogen bromide

  4. When elements form more than one type of ionic compound Roman numerals are used to indicate the charge on the cation.
    Fe2+ and O2-give FeO = Iron(II) Oxide
    Fe3+ and O2- give Fe2O3 = Iron(III) Oxide
    Sn2+ and Cl- give SnCl2= Tin(II) Chloride
    Sn4+ and Cl- give SnCl4= Tin(IV) Chloride

    There is an older system of naming these compounds that uses the Latin name of the metal with the suffices of "-ic" and "-ous" to designate the higher and lower charge of the metal, respectively.

    So the examples above would be, under the older system,

    FeO = Ferrous Oxide
    Fe2O3 = Ferric Oxide
    SnCl2 = Stannous Chloride
    SnCl4 = Stannic Chloride

    Here are some other examples

    Ion Latin NameSystematic Name
    Au+ AurousGold(I)
    Au3+ AuricGold(III)
    Cu+ CuprousCopper(I)
    Cu2+ CupricCopper(II)

  5. For polyatomic ions, you should memorize the names below.

    NH4+ ammonium
    OH- hydroxide
    CN- cyanide
    C2O42- oxalate
    Cr2O72- dichromate
    NO3- nitrate
    SO42- sulfate
    PO43- phosphate
    ClO- hypochlorite
    ClO3- chlorate
    MnO4- permanganate
    HSO4- hydrogen sulfate or bisulfate
    Hg22+ Mercury(I)
    SCN- thiocyanate
    CrO42- chromate
    NO2- nitrite
    SO32- sulfite
    CO32- carbonate
    AsO43- arsenate
    ClO2- chlorite
    ClO4- perchlorate
    HSO3- hydrogen sulfite or bisulfite
    HCO3- hydrogen carbonate or bicarbonate

    • Ions and Ion Names:
    • Ionic Compound Names:

Homework from Chemisty, The Central Science, 10th Ed.

2.57, 2.59, 2.61, 2.63, 2.65, 2.67