Chemical Nomenclature

Chemical nomenclature is an important aspect of chemistry.   Therefore, it is essential to be able to go between name and formula easily.  Historically, chemistry has been plagued with common names.  Chemicals were named whatever someone wanted to call them.  With rare exception, we don’t use common names anymore.  However, there are two chemicals that you must know that use common names. They are water (H2O) and ammonia (NH3).  Most people at least know the formula for water, if you don’t, you do now!
The names of the elements are common names.  There is no system to their names so you just have to learn them.  There is also a small group of compounds that exist as diatomic molecules.  That is they exist with two of the same element in the compound.  For these compounds, the name of the compound is the same as the name of the element because the compound only contains that element.  They are shown below:

Name                Formula

Hydrogen             H2
Nitrogen             N2
Oxygen             O2
Fluorine             F2
Chlorine             Cl2
Bromine             Br2
Iodine                 I2
Astatine             At2

One good way to remember them is they are all of the —gens. (Hydrogen, nitrogen, oxygen and the halogens (F2, Cl2, Br2, I2, At2).
Nowadays, however, there is a system for chemical nomenclature. It is called the IUPAC (International Union for Pure and Applied Chemistry) systematic nomenclature.  It is important to learn this system so you become fluent in the language of chemistry.  This handout is designed to help you.