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Inorganic Nomenclature

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Advanced Placement Chemistry

Lesson plan #4

1 class period

Inorganic Nomenclature

Naming Inorganic Compounds

    • The names and formulas of compounds are essential vocabulary in chemistry.
    • There are now over 13 million known chemical substances. Naming them all would be a hopelessly complicated task if each had a special name independent of all others.
    • The rules for chemical nomenclature are based on the division of substances into different categories.

    • The major division is between organic compounds and inorganic ones.
    • Organic compounds contain carbon, usually in combination with hydrogen, oxygen, nitrogen, or sulfur.
    • All other compounds are called inorganic compounds.
    • We will consider three categories of substances:

    • Ionic compounds
    • Molecular compounds
    • Acids

Names and Formulas of Ionic Compounds

    • Positive Ions (Cations)

    • Cations formed from metal atoms have the same name as the metal:

    • Na+ sodium ion
    • Zn+ zinc ion
    • Al3+ aluminum ion
    • Ions formed from a single atom are called monatomic ions.

    • If a metal can form cations of differing charges, the positive charge is given by a Roman numeral in parenthesis following the name of the metal:

    • Fe2+ iron(II) ion
    • Fe3+ iron(III) ion
    • Cu+ copper(I) ion
    • Cu2+ copper(II) ion
    • Ions with different charges exhibit different properties, such as color.

    • Cations formed from nonmetal atoms have names that end in -ium:

    • NH4+ ammonium ion
    • H3O+ hydronium ion

    • Negative Ions (Anions)

    • Monoatomic (one-atom) anions have names formed by dropping the ending of the name of the element and adding the ending -ide.

    • H- hydride ion
    • O2- oxide ion
    • N3- nitride ion
    • A few simple polyatomic anions also have names ending in -ide:
    • OH- hydroxide ion
    • CN- cyanide ion
    • O22- peroxide ion

    • Polyatomic (many-atom) anions containing oxygen have names ending in -ate or -ite. These anions are called oxyanions. The ending -ate is used for the most common oxyanion of an element. The ending -ite is used for an oxyanion that has the same charge but one less O atom:

    • NO3- nitrate
    • NO2- nitrite
    • SO42- sulfate
    • SO32- sulfite
    • Prefixes are used when the series of oxyanions of an element extends to four members, as with the halogens. The prefix per- indicates one more O atom than the oxyanion ending in -ate; the prefix hypo- indicates one less O atom than the oxyanion ending in -ite:

    • ClO4- perchlorate (one more O than chlorate)
    • ClO3- chlorate ion
    • ClO2- chlorite ion (one less O than chlorate)
    • ClO- hypochlorite (one less O than chlorite)
    • Notice that if you learn the rules just indicated, you need to know only the name for one oxyanion in a series to deduce the names for the other members.

    • Anions derived by adding H+ to an oxyanion are named by adding as a prefix the word hydrogen or dihydrogen, as appropriate:

    • CO32- carbonate ion
    • HCO3- hydrogen carbonate ion
    • PO43- phosphate ion
    • H2PO4- dihydrogen phosphate ion
    • Notice that each H+ reduces the negative charge of the parent anion by one.

    • Ionic Compounds

    • Names of ionic compounds are the cation name followed by the anion name:

    • BaBr2 barium bromide
    • Al(NO3)3 aluminum nitrate
    • Cu(ClO4)2 copper(I) perchlorate (or cupric perchlorate)

Names and Formulas of Acids

    • Acids are an important class of hydrogen-containing compounds and are named a special way.
    • An acid is defined as a substance whose molecules yield hydrogen ions (H+) when dissolved in water.
    • Acids based on anions whose name end in -die.

    • Anions whose names end in -ide have associated acids that have the hydro- prefix and an -ic ending as in:

    • Cl- (chloride) HCl (hydrochloric acid)
    • S2- (sulfide) H2S (hydrosulfuric acid)

    • Acids based on anions whose names end in -ate or -ite.

    • Anions whose names end in -ate have associated acids with an -ic ending, whereas anions whose names end in -ite have acids with an -ous ending. Prefixes in the name of the anion are retained in the name of the acid.

    • ClO- (hydochlorite) HClO (hypochlorous acid)
    • ClO2- (chlorite) HClO2 (chlorous acid)
    • ClO3- (chlorate) HClO3 (chloric acid)
    • ClO4- (perchlorate) HClO4 (perchloric acid)

Prefixes used in naming binary compounds formed between nonmetals.

























Names and Formulas of Binary Molecular Compounds

  • The procedures used for naming binary (two-element) molecular compounds are similar to those used for naming ionic compounds.

  • The name of the element farthest to the left in the periodic table is usually written first.
  • If both elements are in the same group in the periodic table, the lower one is named first.
  • The name of the second element is given an -ide ending.
  • Greek prefixes are used to indicate the number of atoms of each element. The prefix mono- is never used with the first element. When the prefix ends in a or o and the name of the second element begins with a vowel, the a or o is often dropped.