Compounds from Two Nonmetals
No.

1
2
3
4
5
6
7
8
9
10

Prefix

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

Nonmetals and metalloids are chemically similar and form many binary molecular compounds. Some examples show how the names work. Note that the second element ends in -ide.

NO2 nitrogen dioxide
CO carbon monoxide
N2O dinitrogen oxide (old: nitrous oxide)
N2O4 dinitrogen tetroxide (not tetraoxide)
PCl5 phosphorus pentachloride
H2O water (not dihydrogen oxide)
NH3 ammonia (not nitrogen trihydride)

We will see these elements again later when they show up combined in oxyanions such as ClO3-, chlorate - a new set of names to learn there.