Inorganic Nomenclature by linzhengnd


									Chemistry 11 Unit IV – Inorganic Nomenclature                                                     1
                            UNIT IV - INORGANIC NOMENCLATURE

A. The Chemical Elements

1.    The term 'INORGANIC NOMENCLATURE' refers to the naming of elements and
inorganic compounds.

Recall that ELEMENTS are the simplest form of matter that cannot be broken down by
chemical processes. The elements in the periodic table can be represented by one or two
letter symbols.

      The first letter in the symbol is ALWAYS in UPPER CASE (capitals) while
      the second letter, if present, is ALWAYS in LOWER CASE.

                    eg. Pb, C, Na, Cl

      Many elements use the first two letters of the elements name as their symbol.

                    eg. Al, Bi, Li

      When the first two letters have already been used by another element, the first and third
      letters are used.

      eg. Ar = argon        As= arsenic    At= astatine

      Still other elements which were known in ancient times have symbols taken from their
      Latin names.

             eg. Iron = ferrum = Fe                       lead = plumbum = Pb

      A few elements have single letters for their symbols.

             eg. B, C, F,H, I, K, N, O, P, S, U, V, W

2.    The elements on the periodic table can be divided into two general groups, METALS
      and NON METALS.
Chemistry 11 Unit IV – Inorganic Nomenclature                                               2
      Metallic elements are located on the bottom left side of the periodic table and share
      the following properties:

             a) High lustre (reflect light when polished)

             b) Malleable (can be beaten or rolled into sheet)

             c) Ductile (can be stretched into wires)

             d) High melting points

             e) Good conductivity of heat and electricity

             f) Most are solid at room temperature

      Nonmetallic elements are located on the upper right side of the table and share the
      following properties:

             a) dull and lack luster

             b) brittle if solid

             c) poor conductors of heat and electricity

             d) most are gases at room temperature
Chemistry 11 Unit IV – Inorganic Nomenclature                                               3
      There are also a number of elements that lie on the border between metals and nonmetals.
      These elements exhibit both metallic and nonmetallic properties and are
      referred to as 'semi-metals', 'metalloids', or 'semi-conductors'.

             White = metals
             Grey = non-metals

B. Naming IONS

1.    When you go across the columns in the periodic table, there is a pattern found between
      the columns of the table and the charges of the ions (combining capacities or
      ion charges).

      The elements in the middle of the periodic table are ignored for now because many of
      them can form two or more ions with different charges. The charges of these ions
      are indicated in their names.
Chemistry 11 Unit IV – Inorganic Nomenclature                                       4
      The following ions are commonly used and their charges should be memorized.

      Others: Zn, Ag

2.    It is important to remember that metal ions form POSITIVE IONS while nonmetals
      form NEGATIVE IONS (Hydrogen is an exception).

      Some important terms that you should know:

             a) ANIONS are ions with a negative charge

             b) CATIONS are ions with a positive charge

             c) MONATOMIC species are made up of only one atom

             d) DIATOMIC species are made up of two atoms

             e) POLYATOMIC species are made up of many atoms, in general this
                term applies to any species having >1 atom.
Chemistry 11 Unit IV – Inorganic Nomenclature                                                     5

      Use the name of the metal and add the word 'ION'

             eg.       sodium metal (Na) forms the sodium ion

                       aluminum metal (Al) forms the aluminum ion

      For metals that can form ions having more than one possible charge (middle portion of the
      periodic table), the STOCK SYSTEM of naming metal ions is used. For these ions, the
      charge is indicated by a ROMAN NUMERAL in parentheses, immediately
      following the name.
             eg.       Fe3+ = iron (III) ion        Fe2+ = iron (II) ion

                       Pb2+ = lead (II) ion         Pb4+ = lead (IV) ion


      For non-metals, take off the original ending of the elements name and put on an '-IDE'

            ELEMENT NAME           ELEMENT SYMBOL           ION NAME       ION SYMBOL

                   fluorine                    F            fluoride           F-
                   chlorine                    Cl          chloride           Cl-
                   bromine                     Br          bromide            Br-
                    iodine                     I             iodide            I-
                   oxygen                      O             oxide            O2-
                   sulphur                     S           sulphide           S2-
                   nitrogen                    N             nitride          N3-
               phosphorus                      P          phosphide           P3-
Chemistry 11 Unit IV – Inorganic Nomenclature                                                     6
4.    There are several POLYATOMIC ions that are commonly used. Most polyatomic ions
      will have the ending 'ATE' or 'ITE'. It is advisable to memorize the names and charges
      of some of the more common polyatomic ions.

                          2-                             2-                                  3-
      carbonate = CO3                  chromate = CrO4                 phosphate = PO4

                      -                                       2-                         -
      nitrate = NO3                    dichromate = Cr2O7              hydroxide = OH

                               -                          +                             2-
      acetate = CH3COO                 ammonium = NH4                  sulphate = SO4

                                   -                               -                     -
      permanganate = MnO4              hydrogen carbonate = HCO3       chlorate = ClO3

      Page 68-69 Exercise 1-3

C.    Writing and Naming Ionic Compounds

1. An ionic compound is made up of ions.

                       Compounds are NEUTRAL molecules.
 Therefore the sum of the positive ion charges = the sum of the negative ion charges.

Ionic compounds always consist of one positive ion and one negative ion. The first ion is
usually a metallic ion and the second ion is either a negative nonmetallic ion or a negative
polyatomic ion.

Compounds that only consist of two kinds of atoms are called BINARY COMPOUNDS.

Compounds with more than two kinds of atoms are called TERNARY COMPOUNDS. Ternary
compounds must contain a polyatomic ion.


Chemistry 11 Unit IV – Inorganic Nomenclature                                                      7
A CHEMICAL FORMULA consists of the symbols for the atom in the compound and
SUBSCRIPT numbers to indicate the number of each kind of atom.

                                                symbols for atoms

Writing the chemical formula for a chemical name involves three rules:

       i)     ALWAYS write the formula for the positive ion first and write the
              formula for the negative ion second.
                      eg. Oxygen and iron (III)  Fe              O2-

       ii)    Criss cross the number in front of the charges on the ions. If no number is
              shown (eg Cl-, Na+, NO3-) use a '1'. The 'criss-crossing' operation balances the positive
              and negative charges. If there is more than one of a particular polyatomic ion,
              brackets MUST be placed around the formula for the polyatomic ion.
                                            Fe3+       O2-

                                            Fe3+        O2-
                                                   2              3

       iii)   Tidy up the formula by:

              reducing the subscripts (put in lowest terms if possible)

              omit the superscript charges

              omit any subscripts that are '1'

              eg      Fe2O3
Chemistry 11 Unit IV – Inorganic Nomenclature                                                     8
Example IV.1 Writing Chemical Formulas

 Write the chemical formulas for the following:
        a) sodium oxide       =      ________________________________________________
        b) magnesium phosphide = ________________________________________________
        c) tin (IV) sulphate =       ________________________________________________
        d) chromium (II) phosphate = _______________________________________________


      Naming ionic compounds is essentially the reverse procedure of writing their formula.
      The only problem that may arise is when the metal has more than one possible
      charge because you will need to decide what charge the metal has in that
      particular compound.
      There are two possible situations that may arise when naming a compound:

              i)     if the first ion in the compound only has one possible charge, simply write
                     the names of the ions one after another (omit the word 'ion' from their

                     ZnCl2  Zinc2+ =zinc ion       Cl- = chloride ion  zinc chloride

                     Ca(NO3)2  Calcium2+ ion       NO3- = nitrate ion  calcium nitrate

              ii)  If the first ion is a metal known to possess more than one possible
              charge OR a metal which is not on the table of 'Names, Formulae and Charges of
                   Some Common Ions', un-criss cross the subscripts and use them as
              the charges (remember the first ion is positive, the second negative)
                            PbO2  (Pb2+)1 (O1-)2

                     Next, if the known charge on the negative ion should be doubled
                     (or tripled) the charge calculated by the uncriss cross method,
                     then double (or triple) the charges on both the positive and
                     negative ions.
                            (This allows for the possibility that the subscripts were reduced)

                     Since the oxide ion is known to always be O2-, the charges need to be doubled to
                                    (Pb4+)1 (O2-)2
Chemistry 11 Unit IV – Inorganic Nomenclature                                         9
                     Last, use stock notation to write the positive ion name, followed by
                     the negative ion name.

                                  (Pb4+)1 (O2-)2  lead (IV) oxide

Example IV.2 Naming Chemical Compounds
 Name the following compounds:
        a) CaI2      ____________________________________________
        b) Cu2S      ____________________________________________
        c) Ag3PO4 ____________________________________________
        d) Pb(SO4)2 ___________________________________________

You must memorize the 'common names' for two compounds:

              H2O = water         and    NH3 = ammonia
Page 70 – 71, Exercise 4 & 5

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