What is Naming Chemical Compounds?

Chemical compounds are formed when elements are joined together by chemical bonds. These bonds are so strong that the compound behaves like a single substance. Compounds have properties of their own, unique to the elements from which they are made. A compound is a type of molecule with more than one element. You can go here to learn more about Molecules and Compounds.

How Compounds are Named

Chemists have a special way of naming compounds. This is a standard method of naming compounds used by scientists around the world. The name is built from the elements and the construction of the molecule.

Basic Naming Convention

First we will see how to name two-element molecules (binary compounds). The name of a two-element compound has two words.

To get the first word, we use the name of the first element or the element to the left of the formula. To get the second word, we use the name of the second element and change the suffix to “ide” at the end of the word.

Some examples of adding the “ide”:

O = oxygen = oxide
Cl = chlorine = chloride
Br = bromine = bromide
F = fluorine = fluoride

Examples of binary compounds:

NaCl – sodium chloride
MgS – magnesium sulfide
InP = indium phosphide

What if there is more than one Atom?

In the case of more than one atom (for example, there are two oxygen atoms in CO2), you prefix the element based on the number of atoms. Here is a list of prefixes used:

# Atoms
1
2
3
4
5
6
7
8
9
10

Prefix
mono-
di-
tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-

** Note: the “mono” prefix is not used on the first element. For example CO = carbon monoxide.

Examples:

CO₂ = carbon dioxide
N₂O = dinitrogen monoxide
CCL₄ = carbon tetrachloride
S₃N₂ = trisulfur dinitride

How is the order of the elements determined?

When there are two elements in a compound, which element appears first in the name?

If the compound consists of a metallic element and a non-metallic element, the metallic element comes first. If there are two non-metallic elements, the first name is the element on the left side of the periodic table.

Examples:

In a compound containing iron and fluoride, the metal (iron) comes first.

In a compound containing carbon and oxygen, the element on the left of the periodic table (carbon) comes first.

More Complex Naming Rules

See some more complex naming rules below.

Naming Metal-Nonmetal Compounds

If either compound is a metal, the naming convention changes slightly. Using the root method, a Roman numeral is used after the metal to indicate which ion is using the charge.

Examples:

Ag₂Cl₂ = silver (II) dichloride
FeF₃ = iron (III) fluoride

Naming Polyatomic Compounds

Polyatomic compounds use a different suffix. Most of them end with “-ate” or “-ite”. There are a few exceptions that end in “-ide,” including hydroxide, peroxide, and cyanide.

Examples:

Na₂SO₄ = sodium sulfate
Na₃PO₄ = sodium phosphate
Na₂SO₃ = sodium sulfite

Naming Acids

Hydrogen acids use the prefix “hydro-” and the suffix “-ic”.

HF = hydrofluoric acid
HCl – hydrochloric acid

Oxygen-containing oxoacids use the suffix “-ous” or “-ic”. The “-ic” suffix is used for acids with more oxygen atoms.

H₂SO₄ = sulfuric acid
HNO₂ = nitrous acid
HNO₃ = nitric acid