Barrons SAT Subject Test Chemistry, 13th Edition

2. The second element is named as if it were an anion and uses its elemental
   name.


3. Prefixes are used to denote the number of the second element present.
   These prefixes are shown in the table below.


4. The prefix mono- is never used for naming the first element. For example,
   CO is called carbon monoxide, not monocarbon monoxide.

Prefixes Used to Indicate Numbers in Covalent Compounds

The following are examples of covalent compounds formed from the
nonmetals nitrogen and oxygen, using the rules above.

Compound

Systematic Name

Common Name

N 2 O

Dinitrogen monoxide*

Nitrous oxide

NO

Nitrogen monoxide*

Nitric oxide

NO 2

Nitrogen dioxide^

N 2 O 3

Dinitrogen trioxide^

N 2 O 4

Dinitrogen tetroxide*^

N 2 O 5

Dinitrogen pentoxide*^

*Notice that for ease of pronunciation, the final “a” or “o” of the prefix is
dropped if the element begins with a vowel.
To write the formula for binary covalent compounds, use the same steps as
when writing the formula of ionic compounds.

1. The symbol of the first element in the formula is written first, followed by
   the second element.