Chemistry Essentials for Dummies

Chapter 6. Covalent Bonding

Naming Covalent Compounds Made of Two Elements

Binary compounds are compounds made up of only two elements, such as carbon dioxide (CO2). Chemists use prefixes in the names of binary compounds to indicate the number of atoms of each nonmetal present. Table 6-2 lists the most common prefixes for binary covalent compounds.

Table 6-2. Prefixes for Binary Covalent Compounds

Number of Atoms

Prefix

Number of Atoms

Prefix

1

mono-

6

hexa-

2

di-

7

hepta-

3

tri-

8

octa-

4

tetra-

9

nona-

5

penta-

10

deca-

In general, the prefix mono- is rarely used. Carbon monoxide is one of the few compounds that uses it.

Take a look at the following examples to see how to use the prefixes when naming binary covalent compounds (I’ve italicized the prefixes):

CO2: Carbon dioxide

P4O10: Tetraphosphorus decoxide (chemists try to avoid putting an a and an o together with the oxide name, as in decaoxide, so they normally drop the a off the prefix)

SO3: Sulfur trioxide

N2O4: Dinitrogen tetroxide

This naming system is used only with binary, nonmetal compounds, with one exception: MnO2 is commonly called manganese dioxide.