Naming Molecular Compounds
Name ________________
Chem Worksheet 9-2
A molecular compound is a group of atoms held together by a covalent bond. Compounds made
entirely of non-metals are generally molecular compounds. Carbon tetrachloride, CCl4, is an example of a
molecular compound. When naming these compounds prefixes are used to denote how many of each atom
is bonded in the compound. However, the prefix mono- is not used with the first element in the compound,
even if there is only one element. The ending of the second element in the compound is always changed to
–ide, in the same way the ending is changed for monatomic anions.
Rules for naming Molecular Compounds
1. Name the first element using the element’s full name.
2. Name the second element using the –ide ending.
3. Use prefixes to tell how many of each element is present.
(do not use the prefix mono- on the first element).
Naming Prefixes
1
mono2
di3
tri4
tetra5
penta6
hexa7
hepta8
octa9
nona10
deca-
Examples
#1. Write the chemical formula for diphosphorus pentoxide
- this compound contains two phosphorus atoms and five oxygen atoms:
P2O5
#2. Name the following compound: IF7.
iodine heptafluoride
- there is one iodine and there are seven fluorine atoms:
(the prefix mono- is not used on the first element and that the ending of fluorine is changed to –ide.)
Fill in the following table with the missing information.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Formula
SO2
N2O4
P4O10
NO2
N2Cl4
S2Cl2
P2S5
© John Erickson, 2005
Name
Sulfur trioxide
Chlorine dioxide
Carbon disulfide
Xenon difluoride
Iodine trichloride
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
Formula
SF6
SeO2
N2O
BrF5
ClF3
CH4
Name
Tetraphosphorus hexasulfide
Ammonia
Boron trichloride
Carbon dioxide
Carbon monoxide
Iodine monochloride
WS9-2NamingMolec