Naming+Chemical+Compounds

							                    Naming Chemical Compounds
  Rules for Naming Binary Ionic Compounds Containing a Metal Ion With a
                             Variable Charge
A binary ionic compound is composed of ions of two different elements - one of which is a
metal, and the other a nonmetal. For example, iron(III) iodide, FeI3, is composed of iron ions,
Fe3+ (elemental iron is a metal), and iodide ions, I- (elemental iodine is a nonmetal).

Rule 1. The cation is written first in the name; the anion is written second in the name.

Rule 2. The name of the cation is the same as the (neutral) element from which it is derived. The
charge on the cation is indicated using a Roman numeral, in parentheses, immediately following
the name of the cation (e.g., Fe3+ = "iron(III)").

Rule 3. The anion is named by adding the suffix -ide to the root of the element name (e.g., I- =
"iodide").

        Rules for Naming Ionic Compounds Containing Polyatomic Ions
Polyatomic ions are ions which consist of more than one atom. For example, nitrate ion, NO3-,
contains one nitrogen atom and three oxygen atoms. The atoms in a polyatomic ion are usually
covalently bonded to one another, and therefore stay together as a single, charged unit.

Rule 1. The cation is written first in the name; the anion is written second in the name.

Rule 2. When the formula unit contains two or more of the same polyatomic ion, that ion is
written in parentheses with the subscript written outside the parentheses.
        Note: parentheses and a subscript are not used unless more than one of a polyatomic
        ion is present in the formula unit (e.g., the formula unit for calcium sulfate is
        "CaSO4" not "Ca(SO4)").


Rule 3. If the cation is a metal ion with a fixed charge, the name of the cation is the same as the
(neutral) element from which it is derived (e.g., Na+ = "sodium"). If the cation is a metal ion with
a variable charge, the charge on the cation is indicated using a Roman numeral, in parentheses,
immediately following the name of the cation (e.g., Fe3+ = "iron(III)").

Rule 4. If the anion is a monatomic ion, the anion is named by adding the suffix -ide to the root
of the element name (e.g., I- = "iodide").
                             How to Name Ionic Compounds?
        The first word in the name is the name of the cation, and the second word is the name of
the anion. There is no exception to this rule.
        The best way to go about naming ionic compounds is to take a look at the formula and
figure out the names of the cation and anion. When you've got that, just stick them together and
you've got the name of the compound.
        If the cation is a main block element, the name of the cation will just be the name of the
element. So, the Na+ ion is the "sodium" ion. If the cation is a transition metal, check out
whether or not there is more than one possible charge (oxidation number) for that element. For
example, iron can have a charge of either +2 or +3. As a result, the cation whether it has a +2 or
a +3 charge must be specified. Next, put the number after the name of the element in Roman
numerals. For example, the Fe+3 ion just has the name "iron (III)".
If the anion has only one atom in it, then the name of the anion is the same as the name of the
element EXCEPT the end of the element name is taken off and "-ide" is added to the end. Thus,
oxygen becomes "oxide", sulfur becomes "sulfide", phosphorus is "phosphide", etc. If the anion
has more than one atom, then it is a "polyatomic ion", meaning that the anion has more than one
atom. If necessary look up the polyatomic ion name in a table. Thus, OH- is "hydroxide", SO42- is
sulfate, et cetera.

                         Handy methods for naming compounds
                      Naming ionic compounds from the formula
Using an example: Fe2(SO4)3

Step One: Name the cation and anion
The cation is always the first thing, and the anion is always the second thing. In this case,
recognize that Fe is "iron", and that SO4 is the "sulfate" ion. Generally, if one of these ions has
more than one atom in it, look it up in a chart.

Step Two: Figure out if a Roman numeral is needed in the name.
If the cation in the compound is not a transition metal, then a Roman numeral is not needed and
the naming is done. If there is, then it is necessary to figure out whether or not the cation can
exist in more than one charge. If not, then a Roman numeral is not needed. If so, then move on to
Step Three...

Step Three: Figure out what the Roman numeral should be
 A good rule of thumb is that usually the number of anions in the molecule is equal to the charge
on the cation, and that the number of cations is equal to the number of anions. Using the
example, there are three sulfate ions, meaning that iron has a charge of +3. Likewise, since there
are two iron atoms, the sulfate has a charge of -2. Since iron has a charge of +3 in this
compound, the name in this example is iron (III) sulfate.
Step Four: Check the work
Look at the answer from the last step, and ask whether the charges are OK. Is +3 a charge that
iron can have? Is -2 the charge of the sulfate ion? In this case, the answer to both questions is
"yes", and the answer of iron (III) sulfate stands.

But... what if a mistake found when the work is checked?
In this case, find another way to solve the problem. Take the example of FeS. If the problem is
solved using the first three steps, it is found that the formula should be iron (I) sulfide. However,
if the check of this work as in step four, it is found that iron cannot have a charge of +1, only +2
or +3, and sulfur can only have a charge of -2. In a case like this, another way must be found to
solve the problem.
When this happens, look at the anion. In the example of FeS, the anion is the sulfide anion, S-2. If
there is one sulfide ion, this means that the total negative charge in the molecule is -2. As a
result, iron must have a charge of +2 to counterbalance the -2 charge of sulfur. Since iron has a
charge of +2, the name of the compound is iron (II) sulfide.

       Giving the formula of an ionic compound if you're given the name
Copper (II) fluoride will be used as an example to find the formula of an ionic compound:

Step One: Translate the name into the ions
In copper (II) fluoride, the cation is the copper (II) ion and the anion is the fluoride ion.
Hopefully, the copper (II) ion is simply Cu2+ and the fluoride ion is F-. If not, then go back and
review the rules for naming ions above.

Step Two: Put brackets around the ions, but leave the charges on the outside.
In this case, the copper (II) ion would be [Cu]2+ and the fluoride ion would be [F]-1. Never
change anything in these brackets, ever!

Step Three: Put the ions next to each other.
When this is done, [Cu]2+[F]-1 is obtained

Step Four: Cross the charges:
The charge on the cation will be equal to the number of anions, and the charge on the anion will
be equal to the number of cations. In this example, one copper atom (because the charge on
fluorine is -1) and two fluoride ions (because the charge on copper is +2) is obtained. This gives
a formula of: [Cu][F]2

Step Five: Take the brackets away. The final formula for copper (II) fluoride is then CuF2

Exceptions:
IF the charges on the ions can be divided by the same number, then do it before step four. For
example, manganese (IV) oxide, in step three both manganese (IV) and oxygen have charges that
can be divided by two. Instead of crossing the +4 for manganese and the -2 for oxygen, simplify
it so that a +2 for manganese and a -1 for oxygen is crossed.
IF a polyatomic ion, such as sulfate or ammonium, it is necessary to replace the brackets with
parentheses in step five. For example, if [NH4]2O is obtained as the formula for ammonium
oxide at the end of step four, simply replace the brackets with parentheses in step five to give
(NH4)2
                        Other stuff that might have been forgotten above
In no particular order, here's some other stuff about ionic compounds:
     Ionic compounds are usually formed when metal cations bond with nonmetal anions. The
       only common exception to this is when ammonium is the cation - there's no metal in
       ammonium, but it forms ionic compounds anyhow.
     Ions are atoms that have satisfied the octet rule (which states that every atom wants to
       have eight valence electrons, just like the nearest noble gas). If two neutral elements, and
       one wants to gain electrons to be like the nearest noble gas and the other wants to lose
       electrons to be like the nearest noble gas, chances are that they will react with each other
       and make an ionic compound.

                           Polyatomic ions (memorize them!!)

Sulfate               SO42-                   Permanganate          MnO4-
Sulfite               SO32-                   Chlorate              ClO3-
Acetate               C2H3O2-                 Perchlorate           ClO4-
Phosphate             PO43-                   Ammonium              NH4+
Phosphite             PO33-                   Nitrate               NO3-
Carbonate             CO32-                   Nitrite               NO2-
Hydroxide             OH-                     Dichromate            Cr2O72-
Cyanide               CN-                     Chromate              CrO42-

                               Binary Covalent Compounds

The first element in the compound is named first using the name of the element.

The second element is named as though it were an anion (using the root name of the
element and adding the suffix -ide). Even though we know there are no anions in a covalent
compound, the second element is named using the -ide suffix just like in ionic compounds.

Prefixes are used to denote the numbers of each atom present. Since there are no formal
charges on the atoms in covalent compounds, it is more difficult to predict the proportions that
the atoms combine in. This information must be provided in the name of the compound. (note:
the prefix mono is never used with the first element).

       Mono = one             Hexa = six
       Di = two               Hepta = seven
       Tri = three            Octa = eight
       Tetra = four           Nona = nine
       Penta = five           Deca = ten