Transcript Chapter 9 Chemical Names and Formulas

H2O
Chapter 4
“Chemical Names
and Formulas”
Modified and adapted from
Pre-AP Chemistry
Charles Page High School
Stephen L. Cotton
Section 4.3
Naming and Writing Formulas
for Molecular Compounds
 OBJECTIVES:
–Interpret the prefixes in the
names of molecular
compounds in terms of
their chemical formulas.
Section 4.3
Naming and Writing Formulas
for Molecular Compounds
 OBJECTIVES:
–Apply the rules for naming
and writing formulas for
binary molecular
compounds.
Molecular Compounds
 Compounds
where
- both elements have neg. charges
- both elements are from right side
- both element are non-metals
- electrons are shared, not transferred
- they generally have low MP & so can be
a S/L/G
Molecular compounds are…
 made
of just nonmetals
 smallest piece is a molecule
 can’t be held together by
opposite charge attraction
 can’t use charges to figure out
how many of each atom (there
are no charges present)
Molecular compounds are easier!
 Ionic
compounds use charges to
determine how many of each.
–You have to figure out charges.
–May need to criss-cross numbers.
compounds: the name
tells you the number of atoms.
 Molecular
– Uses prefixes to tell you the exact
number of each element present!
Molecular Compounds
 Binary
molecule
– 2 atoms w/ covalent bond

Rules for naming binary molecules
• 1st element has normal name
• 2nd element has ending changed to -ide
• Use prefixes to say how many of each element
• Do not use a prefix with the first element if there
is only one.
– (ex. CO - carbon monoxide)
Molecular Naming Prefixes
1
2
3
4
5
mono
di
tri
tetra
penta
6
7
8
9
10
hexa
hepta
octa
nona
deca
Prefixes

To write the name, write two words:
Prefix & name
Prefix & name -ide
Prefixes

To write the name, write two words:
Prefix name Prefix name -ide
 One exception is we don’t write
mono if there is only one of the first
element.

Prefixes

To write the name, write two words:

Prefix name Prefix name -ide
One exception is we don’t write mono if
there is only one of the first element.
 Normally, we do not have double
vowels when writing names (oa oo)

Name the compounds
Formula
CO2
CO
PCl3
N2P4
SO4
N2O5
S4Cl9
Name
Name the compounds
Formula
CO2
CO
Name
Carbon Dioxide
Carbon Monoxide
PCl3
Phosphorus Trichloride
N2P4
Dinitrogen Tetraphosphide
SO4
Sulfur Tetroxide
N2O5
Dinitrogen Pentoxide
S4Cl9
Tetrasulfur Nonachloride
Write the formulas
1.
2.
3.
4.
5.
6.
7.
8.
9.
dinitrogen monoxide
phosphourus trichloride
sulfur hexafluroride
carbon disulfide
carbon tetrabromide
dinitrogen tetrahydride
boron trichloride
diphosphourus trioxide
hexaselenium monochloride
Write the formulas
1.
2.
3.
4.
5.
6.
7.
8.
9.
dinitrogen monoxide
phosphourus trichloride
sulfur hexafluroride
carbon disulfide
carbon tetrabromide
dinitrogen tetrahydride
boron trichloride
diphosphourus trioxide
hexaselenium monochloride
N2O
PCl3
SF6
CS2
CBr4
N2H4
BCl3
P2O3
S6Cl
Molecular Compounds
–Diatomic molecules
–2 of the same nonmetals
covalently bonded
–are gases
–(ex. H2 = hydrogen gas)
Yes
PxQy
P=H?
Acid Compound
No
>2 Elements?
Yes
No
Yes
P=Metal?
No
2 of Same Elements?
Yes
No
Name Binary
Molecule
-use Prefixes
Name Diatomic
Molecule
Practice by naming these:
 N2O
 NO2
 Cl2O7
 CBr4
 CO2
 BaCl2
= dinitrogen monoxide
(also called nitrous oxide or laughing gas)
= nitrogen dioxide
= dichlorine heptoxide
= carbon tetrabromide
= carbon dioxide
(This one will not use prefixes, since it is
an ionic compound!)
Write formulas for these:
 diphosphorus
pentoxide
 tetraiodine nonoxide
 sulfur hexafluoride
 nitrogen trioxide
 carbon tetrahydride
 phosphorus trifluoride
 aluminum chloride (Ionic compound)
Answers
P2O5
 I4O9
 SF6
 NO3
 CH4
 PF3
 AlCl3
