Naming Covalent
Compounds
SLO 4/14/16
Students will be able to interpret chemical
formulas and naming.
9.3
Naming Binary Molecular
Compounds

Carbon and oxygen combine to form carbon
monoxide (CO) and carbon dioxide (CO2), but
these two invisible gases are very different.
Naming Binary Molecular
Compounds
9.3

Sitting in a room with small amounts of CO2 in the
air would not present any problems. If the same
amount of CO were in the room, you could die of
asphyxiation. A naming system that distinguishes
between these two compounds is needed.
Why is the naming system different
for ionic and covalent compounds?
 Ionic compounds combine on the basis of
charge.


There is only 1 possible combination for most
ions
There are limited possibilities for those with
more than one charge
 Covalent compounds combine by sharing
electrons and can share in different wayssingle, double, or triple bonds, and different
numbers of each element

Since there are many combinations, we need
a different system
Prefixes are used in naming
molecular compounds
 A prefix in the name of a binary molecular
compound tells how many atoms of an element are
present in each molecule of the compound.
Naming Covalent Compounds
1. Name 1st element in the compound & add a
prefix to indicate how many are present.

Don’t use mono- on the first element
2. Name 2nd element by using the root of the
element & adding the suffix –ide.

Then add a prefix to indicate how many are
present.
3. When the name of the element begins with “a”
or “o” and the prefix ends in “a” or “o”, drop the
vowel at the end of the prefix. (For example
monoxide, not monooxide.)
Diatomics
 Diatomic elements are just named using the
element name,

O2 is just oxygen
Writing Covalent Formulas
1. Write the elements indicated in the name
2. Write the subscript after the correct element

The prefixes tell you the subscript of each
element within the formula

Dihydrogen monoxide: H2O
Examples of Covalent Naming
 SO3
 Sulfur Trioxide
 CO
 Carbon Monoxide
 PCl5
 Phosphorous Pentachloride
 SF6
 Sulfur hexafluoride
Classwork
 Reading Assignment: Section 9.3
 Written Assignment: pg. 283, #30, 31, 32