Molecular Compounds
Lesson 9
Chemistry 10
Objective: You will be able to
-identify molecular compounds
-compare characteristics of molecular
compounds to ionic compounds
-write chemical formulas for, and name
molecular compounds.
What is a molecule?
Look at the diagram below. What kind of things
do you notice?
How is this different from ionic compounds?
Periodic table and covalent bonds
Molecules are formed when two or more
nonmetals combine by sharing valence electrons.
Example: CO2 (g)
What is the name of this compound?
Naming these compounds
These molecules must be named differently.
Prefixes are used to indicate how many of each
atom is present in the compound.
Prefixes: mono - 1
di - 2
tri - 3
tetra - 4
penta - 5
hexa - 6
hepta - 7
octa - 8
nona - 9
deca - 10
Examples: CO (g)
N2O (g)
SO3 (g)
CCl4 (l)
PF5 (g)
SF6 (g)
IF7 (g)
C8H18 (l)
Cr(NO3)3•9H2O (s)
Na2CO3•10H2O (s)
Notice from the previous examples how the
name tells us exactly how the molecule is
constructed.
Examples
Try writing the formula for these compounds.
1. nitrogen triiodide
2. dinitrogen trioxide
3. phosphorous pentachloride
Special Names
Some molecular compounds have common
names dating far back into antiquity. These
names must be memorized.
Diatomic Elements
Some elements only exist as molecules at room
conditions (SATP)
These are:
hydrogen H2(g)
nitrogen
N2(g)
oxygen
O2(g)
fluorine
F2(g)
chlorine
Cl2(g)
bromine
Br2(l)
iodine
I2(s)
Special Names
The other molecular elements are:
phosphorous
P4(s)
sulfur
S8(s)
Other common molecular compounds are:
Assignment
Molecular Worksheet p. 2
Reading p.