NOMENCLATURE

  • Compounds composed of nonmetals only
    1. a)Organic
    2. b)Inorganic
    3. Binary
  • Compounds formed between metals and nonmetals.
    1. Cations of fixed ionic charge
    2. Binary
    2. Compounds containing 3 or more atoms
      1. Metals with multiple oxidation states
      2. Binary
    2. Compounds containing 3 or more atoms
      1. Aqueous solutions

    Binary compounds
    Name the less electronegative element first and the more electronegative element second.

    The more electronegative element is named by adding an "-ide" suffix to the element's unambiguous stem.

    IIIA IVA VA VIA VIIA
    B bor C carb N nitr O ox H hydr
      Si silic P phosph S sulf F fluor
          Se selen Cl chlor
          Te tellur Br brom
            I iod


    Compounds composed of nonmetals only

    Nearly all polar-covalent and covalent compounds involve two nonmetals bonded together. Although many nonmetals can exhibit different oxidation numbers, their oxidation numbers properly are not indicated by Roman numerals or suffixes. Instead, elemental proportions are indicated by using a prefix system for both elements.

    Formula Name
    SO2 sulfur dioxide
    SO3 sulfur trioxide
    N2O4 dinitrogen tetroxide
    Cl2O7 dichlorine heptoxide
    CS2 carbon disulfide
    As4O6 tetraarsenic hexoxide


    Compounds formed between metals and nonmetals.

    Binary ionic compounds contain metal cations and nonmetal anions. The cation is named first and the anion second according to the rule described previously.

    Formula Name
    KBr potassium bromide
    CaCl2 calcium chloride
    NaH sodium hydride
    RbS rubidium sulfide
    Al2Se3 aluminum selenide
    SrO strontium oxide

    Metals with multiple oxidation states

    The preceding method is sufficient for naming binary ionic compounds containing metals that exhibit only one oxidation number other than zero. Most transition elements, and few of the more electronegative representative metals exhibit more than one oxidation number. To distinguish among all possibilities, the oxidation number of the metal is indicated by a Roman numeral in parentheses following its name.

    Formula Ox. No. of Metal Name
    Cu2O +1 copper(I) oxide
    CuF2 +2 copper(II) fluoride
    FeS +2 iron(II) sulfide
    Fe2O3 +3 iron(III) oxide

    An older method is still in use but is not recommended by the IUPAC. This method uses "-ous" and "-ic" suffixes to indicate lower and higher oxidation numbers, respectively.

    Formula Ox. No. of Metal Name
    Cu2O +1 cuprous oxide
    CuF2 +2 cupric fluoride
    FeS +2 ferrous sulfide
    Fe2O3 +3 ferric oxide


    Compounds containing 3 or more atoms

    Pseudobinary compounds contain more than two elements. In these compounds one or more of the ions consist of more than one element but behave as simple ions. Some common examples of such anions are the hydroxide ion, OH    -, and the cyanide ion, CN-. As before, the name of the anion ends in "-ide." The ammonium ion, NH4+, is the common cation that behaves like a simple metal cation.

    Formula Name
    NH4I ammonium iodide
    Ca(CN)2 calcium cyanide
    NaOH sodium hydroxide
    NH4CN ammonium cyanide
    Cu(OH)2 copper(II) hydroxide or cupric hydroxide
    Fe(OH)3 iron(III) hydroxide or ferric hydroxide



    Aqueous solutions

    Binary acids are compounds in which H is bonded to the more electronegative nonmetals. These compounds act as acids when dissolved in water. The compounds are name as typical binary compounds. Their aqueous solutions are named by modifying the characteristic stem of the nonmetal with the prefix "hydro-" and the suffix "-ic" followed by the word "acid."

    Formula Name of Compound Name of Aqueous solution
    HCl hydrogen chloride hydrochloric acid
    HF hydrogen fluoride hydrofluoric acid
    H2S hydrogen sulfide hydrosulfuric acid
    HCN hydrogen cyanide hydrocyanic acid

    For ternary and higher compounds, the word "hydrogen" is dropped, and the name of the polyatomic ion is used. "-ate" is replaced with "-ic" and "-ite" is replaced with "-ous"

    Formula Name of Compound Name of Aqueous solution
    HNO2 hydrogen nitrite nitrous acid
    HNO3 hydrogen nitrate nitric acid
    H2SO4 hydrogen sulfate sulfuric acid
    H3PO3 hydrogen phosphite phosphorous acid
    H3PO4 hydrogen phosphate phosphoric acid


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