Naming Binary Molecular Compounds

2 elements covalent bond

3 Rules to Name

1. Name the first element using the entire name2. Second element in the formula- use the root

word and end in –ideex: Oxygen Sulfur Hydrogen

OxideSulfideHydride

3. Add a prefix to both words to indicate the number of atoms

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

2 Exceptions to the rule

1. When the formula contains one atom of the first element, omit mono

ex: CO2 Carbon DioxideNot: Monocarbon Dioxide

2 Exceptions to the rule

2. Drop the final letter in the prefix if the element begins with a vowel

- For prefixes 1 & 4-9ex: CO Carbon monoxide

Not: Carbon monooxide

Example 1

S4N2

sulfur nitrogen

tetra di

nitride

tetrasulfur

dinitride

Example 2

SO3

Only one atom of sulfur

sulfur

- so no prefix needed

oxide

tri

oxygen

tri

Example 3

P4S5

tetra sulfide

penta

sulfurpenta

tetra

phosphorus

Example 4

CO

Only one atom of carbon

carbon

- so no prefix needed

oxide

mono

oxygen

mon NOT monooxide

Example 5

NH3

Only one atom of nitrogen

nitrogen

- so no prefix needed

hydride

tri

hydrogentri More Common

Name is “ammonia”

Example 6

CH4

Only one atom of carbon

carbon

- so no prefix needed

hydride

tetra

hydrogen

tetra More Common Name is “methane”

Example 7-9

Example 7: As2O3

Diaresenic trioxide

Example 8: N2O5

Dinitrogen pentoxide

Example 9: P4O10

Tetraphosphorus decaoxide