1. Molecular Compounds
Science 10

2. Molecular Compounds
IUPAC NAME
FORMULA
water
H2O(l)
hydrogen peroxide
H2O2(l)
ammonia
NH3(g)
hydrogen sulphide
H2S(g)
methane
CH4(g)
propane
C3H8(g)
methanol
CH3OH(l)
ethanol
C2H5OH(l)
sucrose
C12H22O11(s)
There are about 5 million different molecular compounds
Luckily, you only have to memorize 9 of them

3. Molecular Compounds cont.
Molecular compounds are made up of molecules
They form when two non-metal atoms share a pair of electrons
This sharing of electrons is called a covalent bond
Each pair of shared electrons forms one covalent bond
Atoms may form multiple covalent bonds
Covalent bonds are strong
a lot of energy is needed to break them

4. Molecular Properties Can be solid, liquid or gas at room temperature
Do not conduct electricity when in water
Low melting and boiling points

5. Molecular Elements Some elements exist as molecules Monatomic elements
Exist on their own as one atom
Examples include C, Si, noble gases, and all metals
Diatomic elements
Are composed of two atoms
H2(g), N2(g), O2(g), F2(g), Cl2(g), Br2(l), I2(s) and At2(s)
Polyatomic elements
Are composed of more than two atoms
P4(s) and S8(s)

6. Molecular Elements cont.

7. Naming Molecular Compounds
For naming molecular compounds follow these steps:
ALWAYS use lowercase letters
Check to see if it is a formula you should know (from the previous list that must be memorized) and use that name
If it is not on that list, name the first element
Name the second element with “-ide” at the end
Add prefixes indicating number of atoms (except when there is only one atom of the first element - then no prefix is used)

8. Prefixes for Molecular Compounds1
mono- 2
di- 3
tri- 4
tetra- 5
penta- 6
hexa- 7
hepta- 8
octa- 9
nona- 10
deca-

9. Practice as a Class Name Formula P2O5 dinitrogen trioxide
carbon disulfide
PCl3

10. Try it!
Work on your molecular compounds worksheet