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Ionic Formulas

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					Ionic Formulas

Ionic formulas are constructed of particles with opposite charges. The positive particles are referred to as the
cations, the negatively charged particles are the anions. For this section, three types of ionic formulas will be
discussed.

Binary Ionic Formulas - Binary formulas contain two elements. For binary ionic formulas, the first element
in the formula will be the cation and second element will be the anion. An easy way to recognize this type of
formulas, is that the first element will be a metal and the second element will be a nonmetal. So, in general,
the first element in the compound will come from the left side of the periodic table and the second element
will be from the right side. To name a binary ionic compound you will consider the cation and anion
separately. The name of the cation is the regular name of the element.
The ending of the anion is changed to -ide.

Examples:

                                      NaCl - sodium chloride
                                      MgO - magnesium oxide
                                      CaBr2 - calcium bromide

Polyatomic Formulas - Polyatomic ions are made from more that one atom. This group of atoms act
together as one unit with a single charge. Each of the polyatomic ions have a unique name.

Table of Polyatomic Ions

                 1+                          1-                       2-                 3-
          ammonium , NH4 +       acetate, C2H302-          carbonate, CO32-       phosphate, PO43-
                                 bicarbonate, HCO3 -       chromate,CrO42-
                                 bisulfate, HSO4 -         dichromate,Cr2O72-
                                 bisulfite, HSO3 -         oxalate,C2O42-
                                 chlorate,ClO3-            peroxide,022-
                                 chlorite,ClO2-            silicate,SiO32-
                                 cyanide,CN-               sulfate,SO42-
                                 hydroxide,OH-             sulfite,SO32-
                                 hypochlorite,ClO-         tartrate,C4H4062-
                                 iodate,IO3-               thiosulfate,S2O32-
                                 nitrate,NO3-
                                 nitrite,NO2-
                                 perchlorate,ClO4-
                                 permanganate,MnO4-

Most of the polyatomic ions are anions. The formula for the compound will contain both a cation and an
anion to balance the overall charge of the compound. The cation is named normally and the anion is given
the name of the actual anion. An easy way to recognize these formulas is the fact that they are made up of
more that two elements and, usually, the first element is a metal.
Examples:

               Al(C2H3O2)3 - aluminum acetate              KCN - potassium cyanide
                    BaSO3 - barium sulfate                CaSO3 - calcium sulfite
                    Li3PO4 - lithium phosphate           NH4OH - ammonium hydroxide

Multiple Ionic Charges - The ionic charges of several transition metals are variable. For example the copper
ion can either be 1+ or 2+.

Table of Metal Ions with Multiple Valence Numbers


                   antimony (III) - Sb3+                iron (II) - Fe2+   mercury (I) - Hg2+2
                   antimony (IV) - Sb5+                iron (III) - Fe3+   mercury (II) - Hg2+
                   chromium (II) - Cr2+                 lead (II) - Pb2+     nickel (II) - Ni2+
                  chromium (III) - Cr3+               lead (IV) - Pb4+      nickel (III) - Ni3+
                        copper (I) - Cu +        manganese (II) - Mn2+           tin (II) - Sn2+
                                        2+                             4+
                       copper (II) - Cu        manganese (IV) - Mn              tin (IV) - Sn4+
The name of the compound should have a roman numeral placed between the name of the cation and the
anion to indicate the specific charge of the cation being used. To determine this charge you need to
determine what charge is needed to balance the overall compound. To do this multiply the charge of the
anion by the number of anions divide this by the number of cations. This will give the charge for the cation.

Examples:

                         FeO - iron II Oxide               PbO - lead II oxide
                       Fe2O3 - iron III oxide             PbO2 - lead IV oxide
                       CuOH - copper I hydroxide         CrNO3 - chromium II nitrate
                     Cu(OH)2 - copper II hydroxide       CrNO2 - chromium II nitrite


Binary Molecular Formulas - Molecules are compounds that use covalent bonds to join two atoms together.
Binary molecules will only have two elements in their formula. An easy way to determine if the compound
is named in this manner, is the fact that the two elements in the formula will both be nonmetals (or both are
from the right hand side of the periodic table). The names of the compounds will include a prefix to
indicate the number of atoms of each element. There is no need to balance this type of formula. The second
elements name is changed to end in -ide.

Table of Prefixes

                                        one - mono            six -   hexa
                                       two - di            seven -    hepta
                                     three - tri            eight -   octa
                                      four - tetra           nine -   nona
                                      five - penta            ten -   deca

An exception to using the prefixes is when the first element has only one atom. The prefix would be mono is
not used for this instance. Also determining where the words fit together will take some practice.
Examples:

                                         CO2 - carbon dioxide
                                               - carbon
                                         CCl4
                                              tetrachloride
                                         S3N2 - trisulfur dinitride


Acids - Acids dissociate into ions when disolved in water. All of the formulas for acids that are dealt with
in this section will start with the hydrogen ion. In order to name the compound as an acid, first name the
compound as if it were an ionic compound. Use hydrogen as the cation. Then change the name according to
the following table.

Table for Naming Acids


                     Ending of name as an ionic compound                 New form of name
                                     -ide                                hydro-root-ic acid
                                     -ite                                  root-ous acid
                                     -ate                                   root-ic acid
                                                 Examples:
                         Formula          Ionic Name              Acidic Name
                           HCl        hydrogen chloride         hydrochloric acid
                          HNO3         hydrogen nitrate            nitric acid
                          H2SO3        hydrogen sulfite          sulfurous acid

				
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