BINARY MOLECULAR
COMPOUNDS
 molecule:
electrically neutral group of
atoms that acts as a unit
 composed of nonmetals
 electrons are shared (covalent):
NO CHARGES
 no criss-cross, no reducing subscripts
 can combine in more than one way
NAMING BINARY
MOLECULES
 prefixes
used to denote multiple
atoms of one element in a molecule
1
2
3
4
5
mono- 6
di7
tri8
tetra- 9
penta- 10
hexaheptaoctanonadeca-
NAMING BINARY
MOLECULES
element in name ends in –ide
 for oxides: if the prefix ends in
a or o, LEAVE OUT the a or o
 monooxide becomes monoxide
 tetraoxide becomes tetroxide,
etc.
 2nd
NAMING BINARY
MOLECULES
 if
there is ONE atom of the first
element, omit the prefix mono–
 ex: CO
carbon monoxide
NOT monocarbon monooxide
WRITING NAMES
CO
carbon monoxide
CO2 carbon dioxide
N2O dinitrogen monoxide
Cl2O8 dichlorine octoxide
WRITING NAMES
OF2
oxygen difluoride
N2O5 dinitrogen pentoxide
P4O10 tetraphosphorus decoxide
SO3
sulfur trioxide
WRITING FORMULAS
nitrogen trifluoride
disulfur dichloride
NF3
S2Cl2
dinitrogen tetroxide N2O4
carbon tetrachloride CCl4
DIATOMIC MOLECULES
 molecules
with 2 atoms of the same
element
 there are 7 – know them!
N2 O2 H2 Cl2 I2 F2 Br2
or
Br2 I2 N2 Cl2 H2 O2 F2
LEWIS DOT DIAGRAMS
(ELECTRON DOT DIAGRAMS)
 show
the valence electrons as
dots
 inner electrons and atomic nuclei
are represented by the symbol
LEWIS DOT DIAGRAMS
(ELECTRON DOT DIAGRAMS)
1A: 1 valence e group 2A: 2 valence e-, etc.
 group
LEWIS DOT DIAGRAMS
(ELECTRON DOT DIAGRAMS)
 diatomic
molecules
LEWIS STRUCTURES: STEPS
1. Count valence electrons and bonds
using periodic table and octet rule –
make a chart to get valence and
shared electrons
2. Choose an arrangement of atoms
(carbon in center, hydrogen or
halogens on outside)
LEWIS STRUCTURES: STEPS
3. Put in calculated number of bonds;
single bonds first, then multiple
bonds if necessary.
4. Where necessary to complete
octets, put in non-bonding electrons
in pairs.
LEWIS STRUCTURES: STEPS
5. Check work by counting electrons in
Lewis structure and comparing
calculated number of valence
electrons.
LEWIS STRUCTURES
CH2O
C
H
H
O
V
4
1
1
6
12
lO
S
4
H–C–H
1
1
2
8 / 2 = 4 bonds
LEWIS STRUCTURES
NH3
N
H
H
H
V
5
1
1
1
8
S
H–N–H
3
H
1
1
1
6 / 2 = 3 bonds
LEWIS STRUCTURES
SO32–
S
O
O
O
V
6
6
6
6
24
+2
26
S
2
2O–S–O
2
2
O
2
8
-2
6 / 2 = 3 bonds