3.3 Naming Compounds (Nomenclature)
| Types of Compounds | |
|---|---|
| Ionic Compounds | metal w/nonmetal or involving polyatomic ions (ex. NaCl) |
| Molecular Compounds | two nonmetals (ex. H2O) |
| Acids | H with nonmetal or oxyanion (ex. HCl, H2SO4) |
Naming Ionic Compounds
| Naming Ionic Compounds |
|---|
| 1. Name the cation (metal or polyatomic ion). |
| 2. State the metal’s oxidation state as a roman numeral in parenthesis. (except Group I/II metals, Al3+, Zn2+, Cd2+, Ag+) |
| 3. Name the non-metal with an -ide ending (or name the polyatomic anion). |
NaCl MgCl2
CuS Cu2S
NH4Br CuSO4
| Polyatomic Ions | |
|---|---|
| SO42- | sulfate |
| SO32- | sulfite |
| NO3- | nitrate |
| NO2- | nitrite |
| PO43- | phosphate |
| CO32- | carbonate |
| HCO3- | bicarbonate |
| OH- | hydroxide |
| MnO4- | permanganate |
| CrO42- | chromate |
| Cr2O72- | dichromate |
| NH4+ | ammonium |
| CN- | cyanide |
| ClO- | hypochlorite |
| ClO2- | chlorite |
| ClO3- | chlorate |
| ClO4- | perchlorate |
| (for Br and I also) | |
Naming Ionic Compounds Practice
Hover over the boxes below to reveal the name/formula of the molecular compound.
(Don't forget that zinc is an exception--no roman numeral used.)
(Don't forget that zinc is an exception--no roman numeral used.)
Naming Molecular Compounds
Naming molecular compounds is generally easier than naming ionic compounds. A molecular compound is composed of two or more nonmetals, and in this lesson you will specifically learn how to name molecular compounds comprised of exactly two nonmetals (known as binary molecular compounds). There is no worrying about oxidation states and roman numerals as with some ionic compounds. There is simply a numerical prefix added before the name of each element to indicate how many atoms of that element are in a molecule. The rules and numerical prefixes are summarized in the tables below.
| Naming Molecular Compounds (Binary) |
|---|
| 1. Give the numerical prefix of the first element (omit if only one--mono). |
| 2. Name the first element. |
| 3. Give the numerical prefix for the second element. |
| 4. Name the second element with the -ide suffix. |
Name the following molecular compounds (examples in the video lesson):
N2O4 CO2
H2O CO
| Prefixes | |
|---|---|
| 1 | mono |
| 2 | di |
| 3 | tri |
| 4 | tetra |
| 5 | penta |
| 6 | hexa |
| 7 | hepta |
| 8 | octa |
| 9 | nona |
| 10 | deca |
Naming Molecular Compounds Examples
Below the names of several binary molecular compounds are summarized. Note that when there is only one of the 1st element the prefix mono is omitted from the name, but when there is only one of the 2nd element the prefix mono is included.
| Chemical Formula | 1st Prefix | 2nd Prefix | |||
|---|---|---|---|---|---|
| P4O10 | tetra | phosphorus | deca | oxide | tetraphosphorus decoxide |
| N2O5 | di | nitrogen | penta | oxide | dinitrogen pentoxide |
| SF6 | n/a | sulfur | hexa | fluoride | sulfur hexafluoride |
| N2O | di | nitrogen | mono | oxide | dinitrogen monoxide |
| CO | n/a | carbon | mono | oxide | carbon monoxide |
Naming Molecular Compounds Practice
Hover over the boxes below to reveal the name/formula of the molecular compound.
Naming Acids
| Naming Binary Acids | Naming Oxoacids | |
|---|---|---|
| Hydro-element-ic acid | HClO hypochlorous acid | |
| HNO2 nitrous acid | HClO2 chlorous acid | |
| HNO3 nitric acid | HClO3 chloric acid | |
| HClO4 perchloric acid | ||
How to Name Binary Acids
A binary acid generally contains hydrogen and one other element such as HCl or H2S (HCN is considered a binary acid too).
The names for binary acids all follow the same pattern:
hydro-element-ic acid
The only variance is the use of the root of the particular element.
Here are the names of some common binary acids:
HBr hydrobromic acid
H2S hydrosulfuric acid
HI hydroiodic acid
How to Name Oxoacids (aka Oxyacids)
Oxoacids (a.k.a oxyacids) are the acids of the polyatomic oxoanions. These include the following:
HNO3 is the oxoacid of the nitrate ion NO3-
HNO2 is the oxoacid of the nitrite ion, NO2-
To name the corresponding oxoacid, replace the -ic suffix with -ate or the -ite suffix with -ous and then add the word acid:
HNO3 nitric acid
HNO2 nitrous acid
For Cl, Br, and I there are four oxoanions and therefore four corresponding oxoacids. But the same procedure of replacing the suffixes is used so as long as you know the name of the oxoanion you should be able to name the corresponding oxoacid:
| ClO4- perchlorate | HClO4 perchloric acid |
| ClO3- chlorate | HClO3 chloric acid |
| ClO2- perchlorite | HClO2 chlorous acid |
| ClO- hypochlorite | HClO hypochlorous acid |
Name the following molecular compounds (examples in the video lesson):
HCl H2SO3
H2S H2SO4
H2Se
Naming Acids Practice
Hover over the boxes below to reveal the name/formula of the molecular compound.