Chemical Nomenclature

This problem set was developed by S.E. Van Bramer for Chemistry 145 at Widener University.

The following outline is to help you decide how to name a chemical compound. Use it as a flow chart to break down the different systems of naming to determine the name of a compound.

Formulas and Names of Binary Metal-Nonmetal Compounds

  1. The name of the metal is first (ie: NaCl, sodium chloride)

  2. The name of the nonmetal has -ide added (ie: NaCl sodium chloride)

  3. IF the metal has more than one possible charge
    1. With the Stock Method you must indicate which ion using the charge in roman numerals (ie: FeCl2 Iron (II) chloride).

    2. Alternatively the common name may be used if the metal has more than one possible ion. Here use the Latin root and then add -ous for the lower charge. -ic for the higher charge.
      1. FeCl2 ferrous chloride
      2. FeCl3 ferric chloride

    3. More examples showing the two different systems:

      Compound Stock MethodCommon Name
      FeF2iron (II) fluorideferrous fluoride
      FeF3iron (III)fluorideferric fluoride
      Hg2Br2mercury (I) bromidemercurous bromide
      HgBr2mercury (II) bromidemercuric bromide

Formulas and Names of Binary Nonmetal-Nonmetal Compounds

  1. Systematic Nomenclature:
    1. For names start with element to the left side on the periodic table

    2. add -ide to the second element

    3. use Greek prefixes for number of atoms: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

    4. Example:
      1. CO carbon monoxide
      2. CO2 carbon dioxide
      3. N2O5 dinitrogen pentoxide

  2. Common names: -ous and -ic (-ic has greater charge, OR has fewer atoms). Examples:

    FormulaSystematic NameCommon Name
    NO nitrogen monoxide nitric oxide
    N2Odinitrogen monoxide nitrous oxide
    NO2nitrogen dioxidenitrogen peroxide
    N2O5dinitrogen pentoxide nitric anhydride
    N2O3dinitrogen trioxide nitrous anhydride

Polyatomic Compounds.

  1. Names of Polyatomic Ions

    1. Anions are negative, Cations are positive

    2. ammonium ion NH41+

    3. -ide ions
      1. CN1- cyanide
      2. OH1- hydroxide

    4. Oxyanions
      1. -ate ate more oxygen.

        NO21- nitrite
        NO31- nitrate

      2. Sometimes oxyanions have an extra hydrogen

        HSO41-hydrogen sulfate (or bisulfate)

      3. If more than two possibilities:

        ClO1- hypochlorite
        ClO21- chlorite
        ClO31- chlorate
        ClO41- perchlorate

  2. Naming compounds with polyatomic ions
    1. Positive charge species on left (using Stock method or common name)

    2. Negative charge species on right (using name of polyatomic ion)

    3. Use parentheses as needed

      Formula Ions Name
      BaSO4 Ba2+ and SO42- barium sulfate
      Ca(NO3)2 Ca+2 and NO31- calcium nitrate
      Ca(NO2)2 Ca+2 and NO21- calcium nitrite
      Fe(NO3)2 Fe2+ and NO31- iron (II) nitrate or
      ferrous nitrate


  1. Hydro Acids: Hydro + halogen name + ic

    HCl hydrochloric acid
    HF hydrofluoric acid

  2. OxoAcids: polyatomic ion + acid.
    1. Recognize as polyatomic ions with a hydrogen at the beginning of the formula.

    2. Name with -ous and -ic suffix. (Works just like -ite and -ate suffix)

    3. -ic suffix is for acid with more oxygen atoms.

    4. Examples

      Formula Name Source
      HNO3nitric acidnitric from nitrate
      HNO2nitrous acidnitrous from nitrite

Please send comments or suggestions to

Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

© copyright 1996, S.E. Van Bramer
This page has been accessed times since 1/5 /96 .

Last Updated: Wednesday, September 08, 1999 12:35:50 PM