Name: _______________________________
Notes for learning the “Nomenclature” (official naming system) for Binary Molecular Substances
When given a formula for a molecular substance, first determine if it is a formula for one of the 7 diatomic elements, or if it is
the formula for a binary compound.
If you are given the formula for a molecular element, such as “H2”, call it the element’s name, as you have been doing.
Examples: H2 = “hydrogen”, N2 = “nitrogen”, O2 = “oxygen”, F2 = “fluorine”, Cl2 = “chlorine”, Br2 = bromine, I2 = iodine.
If you are given a formula for a binary molecular compound, you may notice that the LESS electronegative element (the
more electropositive element) always come firsts. So, you should address the name of that element first.
Name the first element in 2 steps:
1. Write down a prefix IF there is more than one atom of the first element in the formula.
1. Prefix choices: 2 = di, 3 = tri, 4 = tetra, 5 = penta, 6 = hexa, 7 = hepta, 8= octa, 9 = nona, 10 = deca.
11 = undeca, 12 = dodeca.
2. Write the entire element’s name (as it is written on the periodic table)
Example: for PCl3
the molecule’s name begins with “phosphorus”
Example: for H2O
the molecule’s name begins with “dihydrogen”
Example: for OCl2
the molecule’s name begins with “oxygen”
Example: for ClF2
the molecule’s name begins with “chlorine”
Example: for Cl2O
the molecule’s name begins with “dichlorine”
Name the second element in 3 steps:
1. Write down a prefix, EVEN IF there is only 1 atom of the first element in the formula. 1 = mono. Other prefixes same
as above.
2. Write down the root (or stem) of the second element’s name (similar to what you used for ionic compound anions)
3. Write down the ending replacement, “-ide”.
Example: for PCl3
the molecule’s entire name is “phosphorus trichloride”
Example: for H2O
the molecule’s entire name is “dihydrogen monoxide”
Example: for OCl2
the molecule’s entire name is “oxygen dichloride”
Example: for ClF2
the molecule’s entire name is “chlorine difluoride”
Example: for Cl2O
the molecule’s entire name is “dichlorine monoxide”
Confusing Ideas:
The element chlorine’s molecular formula is “Cl2” and to name this formula you should write, “chlorine”.
But, when “Cl2” is the second part of a binary molecular compound, such as in “OCl2”, the “Cl2” part is called “dichloride”.
And, when “Cl2” is the first part of a binary molecular compound such as in “Cl2O”, the “Cl2” part is called “dichlorine”.
Writing a formula when given a name ….Think backwards.
1.
Are you given the name of a binary molecular compound or a diatomic element?
a. If it’s a diatomic element, Write down the symbol (from the periodic table) and add a subscript of 2.
Example: Write the formula for “hydrogen”. Answer: H2
2. Are you given the name of a binary molecular compound?
a. Write down the symbol of the 1st element, follow it by a subscript (if a prefix was given as part of its name).
b. Write down the symbol of the 2nd element, follow it by a subscript (if the prefix indicates more than 1 atom).
If you need further clarification in order to begin the practice sheet, you should read pp. 268 – 270 in your textbook.
There will be ~ 30 points of naming and formula writing for molecular substances on the unit 3 test.
Name: ____________________________________
Practice naming the following molecular substances:
Practice writing formulas for the following molecular substances:
1.
PCl3
a. dinitrogen tetroxide
2.
O2
b. Carbon tetrachloride
3.
Si2Br6
c. oxygen
4.
CCl4
d. diphosphorus pentoxide
5.
H2O
e. disulfur dichloride
6.
P2O5
f.
7.
Cl2
g. iodine heptafluoride
8.
SiO2
h. Fluorine nitrogen trifluoride
9.
P4F5
i.
dinitrogen monoxide
10. N2O5
j.
iodine
11. N2O3
k. Dinitrogen trioxide
12. SF6
l.
13. SO3
m. phosphorus pentabromide
14. ClF3
n. Hydrogen
15. SeO2
o. Selenium hexafluoride
16. CO2
p. carbon disulfide
17. H2
q. Bromine
18. P4S5
r.
19. N2O5
s. chlorine dioxide
20. CO
t.
21. N2
u. iodine pentafluoride
22. SF6
v. dinitrogen trioxide
tetraphosphorus decoxide
silicon dioxide
hexaboron monosilicide
fluorine
w. nitrogen
23. SbBr3
24. ClO2
25. PI3
x. Phosphorus pentabromide
y. Dinitrogen tetroxide
z. Sulfur dioxide
aa. Nitrogen