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.

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.