1. Today’s goals
Learn the naming system for molecules—covalently bonded substances.
Memorize the prefixes necessary to describe the number of atoms in each molecule.
Apply to naming of formulas.

2. Homework Review

3. Ionic or molecular?
KCl
NO3
KClO3

4. Naming Molecular Compounds
Before we do this there is a small matter of exceptions to the rules in ionic naming.
Mercury—always appears as two.
Peroxide—always two. H2O2
H in front is a + so is an acid—we will name those later.
H on the right is a negative ion, so is a “hydride”.
So H can be both.

5. Naming Molecular Compounds
This system is a little bit different.
It is used when non metals combine.
Since there is no way to tell how many atoms combine we simply tell you in the name.
However, to let you know it is molecular, we use a different system for one, two three etc.

6. The numbering system No Roman Numerals are used.
We have abbreviations for 1-10, called prefixes that are used in front of the name.
1. mono hexa
2. di hepta
3. tri octa
4. tetra nona
5. penta 10. deca
Binary compounds still end in “ide”.
There are some exceptions: mono is not used in front of compounds. No names start with “mono”.

7. To Name:
1. Use the name of the first element.
Put a prefix in front unless there is only one atom.
Change the second name to end in “ide”
Use a prefix!!
Examples:
N2O dinitrogen monoxide
PCl phosphorus trichloride
SF sulfur hexaflouride

8. There’s no plus or minus….so who goes first?
The element with the lower group goes first.
Example: Nitrogen and oxygen combine.
Put nitrogen first---NO2
Exception!!! With oxygen and a halogen, the halogen goes first. Ex chlorine dioxide. ClO2
If you are in the same group, the element with the higher period goes first.

9. Name it!!
CO2
N2O5
SF6
SO3
S2Cl2
Si3N4
carbon dioxide
dinitrogen pentoxide
sulfur hexaflouride
sulfur trioxide
disulfur dichloride
trisilicon tetranitride

10. Exceptions to the “rules”
Some compounds have common names we use instead of their chemical names.
Water---H2O (dihydrogen monoxide)
Ammonia—NH3 (nitrogen trihydride)
Methane—CH4 (carbon tetrahydride)
Sugar—C6H12O6 (hexacarbon ??? Now you see)

11. Let’s practice!!