Naming Molecules
Using the Traditional System
Learning Goals
Aim: How do we name molecules using the traditional
system
Key Words: molecules, Stock System, IUPAC, traditional
system, Greek numerical prefixes & electromagnetism.
Essential Questions:
1.  What do the roman numerals in a stock system name
indicate? What do the Greek numerical prefixes in a
traditional name indicate?
2.  What are the rules for naming a molecule using the
traditional system? Explain.
3.  What is the process for writing a chemical formula
based on a traditional system molecule name.
Do Now
Transfer The Stock System name of the following molecular
compounds from your homework to the board.
Stock System Name (IUPAC)
Traditional Name
2. CO2
carbon dioxide
4. SO3
sulfur trioxide
7. N2O3
dinitrogen trioxide
14. SCl6
sulfur hexachloride
12. PCL5
potassium pentachloride
15 P2O5
diphosphorous pentaoxide
16 CCl6
carbon hexachloride
19 OF2
oxygen difloride
Greek Numerical Prefixes
1
2
3
4
5
6
7 8
9
10
Rules
1.  The least electromagnetic element is named first,
using the element’s full name.
2.  The most electromagnetic element is named
second as an Anion with suffix "-ide.”
3.  Prefixes are used to denote the number of atoms
for each of the elements.
4.  "Mono-" is not used in the name of the first element.
Practice
Formula
Common Name
CH4
methane
NH3
ammonia
H2O
water
Traditional System Name
Learning Check
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a. CO
______________________________________________
b. SO2
______________________________________________
c. CO2
______________________________________________
a. nitrogen dioxide
________________________________
b. carbon disulfide
________________________________
d. PCl3 ______________________________________________
c. disulfur dibromide
________________________________
e. N2O4 ______________________________________________
d. dichlorine heptoxide
________________________________
e. silicon tetrafluoride
________________________________
f. SF6
______________________________________________
g. P4O10 ______________________________________________
f. tetraphosphorus hexasulfide ________________________________
h. N2O3 ______________________________________________
i. Cl2O
______________________________________________
j. NF3
_____________________________________________________________
%
g. iodine pentafluoride
________________________________
h. xenon trioxide
___________________________________________ %
Class Notes
I.  Naming Molecules Using the Traditional System
A.  Rules
1.  The least electromagnetic element is named first, using the element’s
full name.
2.  The most electromagnetic element is named second as an Anion with
suffix "-ide.”
3.  Prefixes are used to denote the number of atoms for each of the
elements.
4.  "Mono-" is not used in the name of the first element.
B.  Greek Numerical Prefixes
1. 
2. 
3. 
4. 
mono-­‐‑ di-­‐‑
tri-­‐‑
tetra-­‐‑ 5.  penta-­‐‑
6.  hexa-­‐‑
7.  hepta-­‐‑
C.  Examples include the following:
o  CH4
carbon tetrahydride
o  NH3
nitrogen trihydride
o  H2 O
dihydrogen Oxide
8.  octa-­‐‑
9.  nona-­‐‑
10.  deca-­‐‑