3.3 Naming Compounds (Nomenclature)

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Table of Contents
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    Types of Compounds
    Ionic Compounds metal w/nonmetal or involving polyatomic ions (ex. NaCl)
    Molecular Compounds two nonmetals (ex. H2O)
    Acids H with nonmetal or oxyanion (ex. HCl, H2SO4)

    Naming Ionic Compounds

    Naming Ionic Compounds
    1. Name the cation (metal or polyatomic ion).
    2. State the metal’s oxidation state as a roman numeral in parenthesis.
    (except Group I/II metals, Al3+, Zn2+, Cd2+, Ag+)
    3. Name the non-metal with an -ide ending (or name the polyatomic anion).

    NaCl                                             MgCl2


    CuS                                              Cu2S


    NH4Br                                          CuSO4


    Polyatomic Ions
    SO42- sulfate
    SO32- sulfite
    NO3- nitrate
    NO2- nitrite
    PO43- phosphate
    CO32- carbonate
    HCO3- bicarbonate
    OH- hydroxide
    MnO4- permanganate
    CrO42- chromate
    Cr2O72- dichromate
    NH4+ ammonium
    CN- cyanide
    ClO- hypochlorite
    ClO2- chlorite
    ClO3- chlorate
    ClO4- perchlorate
    (for Br and I also)

    Naming Ionic Compounds Practice

    Hover over the boxes below to reveal the name/formula of the molecular compound.

    barium nitrate
    iron (III) bromide
    zinc hydroxide

    (Don't forget that zinc is an exception--no roman numeral used.)

    potassium sulfite
    titanium (IV) oxide
    cadmium sulfide

    (Don't forget that zinc is an exception--no roman numeral used.)

    Naming Molecular Compounds

    Naming molecular compounds is generally easier than naming ionic compounds.  A molecular compound is composed of two or more nonmetals, and in this lesson you will specifically learn how to name molecular compounds comprised of exactly two nonmetals (known as binary molecular compounds).  There is no worrying about oxidation states and roman numerals as with some ionic compounds.  There is simply a numerical prefix added before the name of each element to indicate how many atoms of that element are in a molecule.  The rules and numerical prefixes are summarized in the tables below.

    Naming Molecular Compounds (Binary)
    1. Give the numerical prefix of the first element (omit if only one--mono).
    2. Name the first element.
    3. Give the numerical prefix for the second element.
    4. Name the second element with the -ide suffix.
    Naming Molecular Compounds dinitrogen tetroxide

    Name the following molecular compounds (examples in the video lesson):

    N2O4                                            CO2


    H2O                                              CO

    1 mono
    2 di
    3 tri
    4 tetra
    5 penta
    6 hexa
    7 hepta
    8 octa
    9 nona
    10 deca

    Naming Molecular Compounds Examples

    Below the names of several binary molecular compounds are summarized.  Note that when there is only one of the 1st element the prefix mono is omitted from the name, but when there is only one of the 2nd element the prefix mono is included.

    Chemical Formula 1st Prefix 2nd Prefix
    P4O10 tetra phosphorus deca oxide tetraphosphorus decoxide
    N2O5 di nitrogen penta oxide dinitrogen pentoxide
    SF6 n/a sulfur hexa fluoride sulfur hexafluoride
    N2O di nitrogen mono oxide dinitrogen monoxide
    CO n/a carbon mono oxide carbon monoxide

    Naming Molecular Compounds Practice

    Hover over the boxes below to reveal the name/formula of the molecular compound.

    carbon dioxide
    diphosphorus pentoxide
    carbon tetrachloride
    oxygen difluoride
    carbon disulfide
    phosphorus pentachloride

    Naming Acids

    Naming Binary Acids Naming Oxoacids
    Hydro-element-ic acid HClO      hypochlorous acid
    HNO2     nitrous acid HClO2     chlorous acid
    HNO3     nitric acid HClO3     chloric acid
    HClO4     perchloric acid

    How to Name Binary Acids

    A binary acid generally contains hydrogen and one other element such as HCl or H2S (HCN is considered a binary acid too).


    The names for binary acids all follow the same pattern:


    hydro-element-ic acid


    The only variance is the use of the root of the particular element. 


    Here are the names of some common binary acids:

    HBr     hydrobromic acid

    H2S    hydrosulfuric acid

    HI       hydroiodic acid

    How to Name Oxoacids (aka Oxyacids)

    Oxoacids (a.k.a oxyacids) are the acids of the polyatomic oxoanions.  These include the following:

    HNO3 is the oxoacid of the nitrate ion NO3-

    HNO2 is the oxoacid of the nitrite ion, NO2-


    To name the corresponding oxoacid, replace the -ic suffix with -ate or the -ite suffix with -ous and then add the word acid:

    HNO3       nitric acid

    HNO2       nitrous acid


    For Cl, Br, and I there are four oxoanions and therefore four corresponding oxoacids.  But the same procedure of replacing the suffixes is used so as long as you know the name of the oxoanion you should be able to name the corresponding oxoacid:

    ClO4- perchlorate HClO4 perchloric acid
    ClO3- chlorate HClO3 chloric acid
    ClO2- perchlorite HClO2 chlorous acid
    ClO- hypochlorite HClO hypochlorous acid

    Name the following molecular compounds (examples in the video lesson):

    HCl                                                         H2SO3


    H2S                                                        H2SO4



    Naming Acids Practice

    Hover over the boxes below to reveal the name/formula of the molecular compound.

    hydrochloric acid
    hydrosulfuric acid
    hydroselenic acid
    hydrofluoric acid
    phosphoric acid
    bromous acid
    carbonic acid
    hypoiodous acid
    HIO or HOI