NOMENCLATURE
Whenever you have a compound, it can be given a name as well as a chemical formula.
There are 3 rules for determining these names:
1. Take the elements in the formula: for example, NaCl.
a. Simply add the names of the resulting ions together, Sodium and chloride, to
give you sodium chloride.
2. However, what happens when you get a compound like PCl3?
a. You can’t simply call it phosphorous chloride. This is because this doesn’t tell
you how many chlorine atoms there are, so what is to distinguish it from PCl5
for example?
b. The solution is to add a prefix to the chloride bit.
i. The prefix is used to denote the number of atoms of an element in a
compound:
 “mono” = 1
 “di”
=2
 “tri”
=3
 “tetra” = 4
 “penta’ = 5
c. So the proper name for PCl3 is phosphorous trichloride.
(And PCl5 would be Phosphorous Pentachloride.)
d. Another example of this is CO2 and CO.
i. CO2 is carbon dioxide.
ii. CO is carbon monoxide.
3. The final rule states that if there is oxygen as well as two or more elements in a
compound, then you change the suffix from “ide” to “ate”
a. For example, NaClO3
i. This is not called sodium trioxide chloride. Instead, you take out the
oxide, and replace the “ide” at the end of chloride with “ate”.
b. This gives you Sodium Chlorate. This is the proper name for the molecule.