Naming Chemical Compounds

      Naming Ionic Compounds
      Naming Nonmetal Binary Compounds
      Naming Compounds with Transition Metals
      Naming Polyatomic Ions

Naming Ionic Compounds
When a metal and a nonmetal combine to form a new substance:

  • The first one retains its name
  • The second one gets the ending: "___ide"

    For example:
    When sodium (Na) combines with chloride (Cl) to form NaCl, the name of the resulting compound is sodium chloride.

    Here are some examples:

    Ionic Compounds
    Formula Name
    MgBr2 magnesium bromide
    CaO calcium oxide
    HF hydrogen fluoride
    LiH lithium hydride

    Naming Nonmetal Binary Compounds

    In the case where two nonmetals combine, we still use the previous rules:

  • The first one retains its name
  • The second one gets the ending: "___ide"
    but we also need to specify the NUMBER of each by using a prefix.

    I try to avoid memorization whenever possible, but unfortunately, these prefixes have to be memorized. You're probably familiar with many of them though, as they're used in the "nonchemistry world":

    Binary Compounds: Nonmetal Prefixes
    # atoms prefix example name
    1 mon(o)___ CO carbon monoxide
    2 di___ CO2 carbon dioxide
    3 tri___ BCl3 boron trichloride
    4 tetr(a)___ CCl4 carbon tetrachloride
    5 pent(a)___ PCl5 phosphorus pentachloride
    6 hex(a)___ SF6 sulfur hexafluoride
    7 hept(a)___ IF7 iodine heptafluoride

    Here are some examples:

    Formula Name
    NO nitrogen monoxide
    NO2 nitrogen dioxide
    N2O dinitrogen monoxide
    N2O3 dinitrogen trioxide
    N2O4 dinitrogen tetroxide
    N2O5 dinitrogen pentoxide
    NI3 nitrogen triiodide

    Be sure to note the spelling of that last example. It's not different in terms of the rules, so don't forget that second i:
    NI3 is nitrogen triiodide

    Naming Compounds with Transition Metals

    Transition metals, the group of metals located in the center region of the periodic table, have more than one possible cation. For example:
    Iron can exist as Fe2+ and as Fe3+

    Because of this, we need to specify the charge on the transition metal.

    We write Fe2+ this way:
            Iron(II) because it has a 2+ charge.

    We write Fe3+ this way:
           Iron(III) because it has a 3+ charge.

    Notice how Roman Numerals are used, within parentheses.

    And don't forget the first rule we used:

  • The first one retains its name
  • The second one gets the ending: "___ide"

    Once again, here are some examples:

    Formula Ions Involved Name
    FeCl2 Fe2+ Cl1- iron(II) chloride
    FeCl3 Fe3+ Cl1- iron(III) chloride
    PbBr4 Pb4+ Br1- lead(IV) bromide
    MnO2 Mn4+ O2- manganese(IV) oxide

    Note that last example, manganese(IV) oxide:
            Mn4+ O2-
    When you cross the charges, as some people do to determine the formula, you get:
            Mn2O4
    but this is not the empirical (simplest) formula! Therefore, we need to simplify it to:
            MnO2

    Naming Polyatomic Ions

    Polyatomic ions are a "cluster" of ions with a net electrical charge.
    The name is taken from the central atom.

    For example, the sulfate ion consists of four oxygen atoms surrounding a central sulfur atom. So the name reflects the central sulfur atom.
    Its formula is: SO42-
    And the net electrical charge is 2-.

    Sometimes, "versions" of a polyatomic ion exist. A sulfur atom may be surrounded by four oxygen atoms, as in the sulfate ion. It may also be surrounded by three oxygen atoms, as in the sulfite ion.

    When two different "versions" exist:

  • the ion with more atoms is named: "___ate"
  • the ion with fewer atoms is named: "___ite"

    So:
            SO42- is the sulfate ion and
            SO32- is the sulfite ion

    When four different "versions" exist:

  • the ion with the 4 surrounding atoms is named: "per___ate"
  • the ion with 3 surrounding atoms is named: "___ate"
  • the ion with 2 surrounding atoms is named: "___ite"
  • the ion with 1 surrounding atom is named: "hypo___ite"

    Here are some examples of polyatomic ions:

    Formula Name
    SO42- sulfate
    SO32- sulfite
    NO31- nitrate
    NO21- nitrite
    ClO41- perchlorate
    ClO41- perchlorate
    ClO31- chlorate
    ClO21- chlorite
    ClO1- hypochlorite
    BrO41- perbromate
    BrO31- bromate
    BrO21- bromite
    BrO1- hypobromite

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