2.3 Naming Molecular Compounds

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    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.

    Rules for Naming Molecular Compounds

    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
    Numerical Prefixes
    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.

    CO2
    carbon dioxide
    P2O5
    diphosphorus pentoxide
    CCl4
    carbon tetrachloride
    oxygen difluoride
    OF2
    carbon disulfide
    CS2
    phosphorus pentachloride
    PCl5