Rule 1: Use number prefixes to tell how many of each
type of atom is in the molecule.
| 1 = mono | 6 = hexa | |
| 2 = di | 7 = hepta | |
| 3 = tri | 8 = octa | |
| 4 = tetra | 9 = nona | |
| 5 = penta | 10 = deca |
Exception: We do not use the prefix mono for the first atom in the name, only the second.
Note: When the second element is oxygen, usually the "a" at the end of the prefix is eliminated (tetroxide).
Rule 2: The ending of the name of the second atom is changed to "ide".