Chemical Nomenclature: Who Are You?
Ionic Compounds
In order to name a chemical compound we must have some knowledge of the type of compound
we are naming. We will begin with Ionic Compounds as they have the simplest rules and once we
master the techniques of naming ionics we can move on to more complicated Covalent Molecules.
*Generally an ionic compound is made of a metal and a non-metal.
*If there is any doubt use the electronegativity difference to be sure (EN) (we will revisit this later)
*If a polyatomic ion is present the compound is ionic
Stepwise Method for Naming Ionic Compounds
1. Name the metal first (ie. NaCl, sodium chloride)
2. The name of the nonmetal has -ide added (ie: NaCl sodium chloride)
3. If the metal has more than one possible charge, we must indicate which
oxidation state (charge) is present using the Stock Method; it indicates the
ion by writing the charge in roman numerals (ie: FeCl2 Iron (II) chloride).
Polyatomic Ions
A polyatomic ion is a molecule that, rather than being neutral carries a charge
(either positive or negative). There are many polyatomic ions, all that we will
examine can be found on your Magic Sheet. A sample of some polyatomics
can be found in the table to the right.
Naming a Compound with a Polyatomic Ion
The process is nearly identical to a binary ionic.
Consider NaNO3:
1. Name the metal, sodium (Na)
2. Name the polyatomic ion, nitrate (NO3-)
3. Name the compound, sodium nitrate
Compound
FeF2
FeF3
Hg2Br2
HgBr2
Name of Ion
cyanide
sulfate
phosphate
carbonate
chromate
silicate
nitrite
nitrate
hydroxide
ammonium
Stock Method
iron (II) fluoride
iron (III) fluoride
mercury (I) bromide
mercury (II) bromide
Formula
CNSO4-2
PO4-3
CO3-2
CrO4SiO3NO2NO3OHNH4+
Charge
-1
-2
-3
-3
-1
-1
-1
-1
-1
+1
Using a Polyatomic Ion to Determine the Charge on a Metal
Consider Fe(OH)2
1. Use the polyatomic ion to determine the charge of the metal, OH- is -1, 2 OH-‘s in the formula therefore Fe must be +2
2. Name the metal using Stock Method, iron (II) (Fe)
3. Name the anion, hydroxide (OH-)
4. Name the compound, iron (II) hydroxide
Number
Prefix
1
monoHydrates
2
diMany ionic compounds also have water molecules attached to the formula; these do not
3
triaffect the name of the ionic compound; however we must have a way to account for
4
tetrathem within the name. We refer to them as hydrates. We use the covalent prefixes to
5
pentaindicate the number of H2O molecules present in a hydrate. Covalent prefixes  
6
hexa.
7
heptaConsider CuSO4 5H2O
8
octacopper (II) sulfate pentahydrate
9
nona10
decaCovalent Molecules
When we name a covalent molecule the process is very similar to that used for an ionic compound. The
difference lies in the use of prefixes. ***Covalent molecules are typically made up of two or more nonmetals and we cannot determine the number of atoms in a covalent compound simply by naming the
first and second element.***
For example: carbon (C) and oxygen (O) can combine to form CO and CO2 (also CO32- but we will
neglect this for the time being). If we were to use the ionic naming system we would get for each case
carbon oxide, which does not tell the two molecules apart. To this end we need to use the prefixes:
mono, di, tri, tetra etc.
To name covalent compounds use the following method
prefix + first element + prefix + root of second element + ide (the prefix "mono" is assumed, and therefore dropped)
Exceptions:
1. H2O is water, not dihydrogen oxide.
2. NH3 is ammonia, not nitrogen trihydride.
3. CO is carbon monoxide, but in all other cases, the mono is dropped.
Examples
1. SO2 (sulfur dioxide)
2. Si3P6 (trisilicon hexaphosphide)
3. BF3 (boron trifluoride)
4. CO2 (carbon dioxide)
5. S5F (pentasulfur fluoride)
Naming Acids, that pesky H atom!
An acid is a special kind of compound. When it is dissolved in water, an acid releases a hydrogen ion (H+) into solution.
Even though many acids are made from two non-metals (H and F, Cl, Br, I) we treat them as ionic compounds.
We can tell a compound is an acid by indicating its state:
o HCl(g) is hydrogen chloride gas
o HCl(aq) is hydrochloric acid because (aq) means aqueous or dissolved in water
To name an acid if it is binary (having hydrogen and either F-, Cl-, Br- or I-)
1. hydro ________ic acid (fluor, chlor, brom, iod)
2. HBr(aq) is hydrobromic acid
To name an acid with a polyatomic ion
1. Replace the suffix “ate” with “ic” and add “acid” to complete the name
2. Replace the suffix “ite” with “ous” and add “acid” to complete the name
3. HNO3 (aq) (hydrogen nitrate, becomes “nitric acid”)
4. HNO2 (aq) (hydrogen nitrite becomes “nitrous acid”)
Complete each of the following exercises for practice
Name
Formula
CuSO4 . 5H2O
Sodium hydroxide
K3As
Cupric chloride
FeCO3
Sodium phosphate tetrahydrate
Sb2(Cr2O7)3
Rubidium selenide
Ca3P2
Cobalt (III) nitrate
Na3PO3
Manganese (II) arsenide
Cs2C2O4
Bismuth (V) phosphate
Hg(NO3)2
Barium bromide
Li2SiO3
Palladium (IV) sulfite
Na2S2O3
Strontium telluride
KMnO4
Mercurous cyanide
MgSO4 . 6H2O
Sodium bicarbonate
NH4ClO4
CS2
N2H4
SiF6
dinitrogen monoxide
P2O5
oxygen difluoride
PCl3
SiO2
sulfur trioxide
hydrochloric acid
HBr (aq)
HI (aq)
HNO2 (aq)
HNO3 (aq)
perchloric acid
H2SO4 (aq)