Molecular Models Activity
carbon tetrachloride
ammonia
methane
hydrogen monochloride
water
trichloromethane
ethane
urea
ethyne
propane
dihydrogen monosulfide
butane
carbon dioxide
nitrogen triiodide (video)
supplies
Lewis Structures
1) Count up total number of valence electrons
2) Connect all atoms with single bonds
- “multiple” atoms usually on outside
- “single” atoms usually in center;
C always in center,
H always on outside.
3) Complete octets on exterior atoms (not H, though)
4) Check
- valence electrons math with Step 1
- all atoms (except H) have an octet; if not, try multiple bonds
- any extra electrons? Put on central atom
Bonding and Shape of Molecules
Number
of Bonds
Number of
Unshared Pairs
0
3
0
4
0
3
1
2
2
Shape
Examples
-Be-
Linear
BeCl2
Trigonal planar
BF3
Tetrahedral
CH4, SiCl4
Pyramidal
NH3, PCl3
Bent
H2O, H2S, SCl2
B
C
:
2
Covalent
Structure
:
N
O:
Carbon tetrachloride
Cl
Cl C Cl
Cl
CCl4
Cl
C
Cl
109.5o
Cl
Cl
Tetrahedral geometry
Carbon tetrachloride – “carbon tet” had been used as dry cleaning solvent
because of its extreme non-polarity.
Methane
H
HCH
H
H
C
H
109.5o
H
H
Tetrahedral geometry
Methane –The first member of the paraffin (alkane) hydrocarbons series.
a.k.a. (marsh gas, CH4).
Water
d(-)
SO2
Bent
geometry
O
H
H
d(+)
Polar molecule
Ethane
C = 1s22s22p2
H H
HC CH
H H
Lewis dot notation
ball-and-stick
C2H6
molecular formula
space-filling molecule
Ethane
H H
HC CH
H H
Lewis dot notation
ball-and-stick
C2H4
molecular formula
space-filling molecule
Ethyne
No octet
each C “feels” 6 electrons
HC CH
C2H2
HC CH
each C “feels” 7 carbons
Ethyne – a.k.a. “acetylene”
6 electrons = triple bond
HC CH
Stable octet
Dihydrogen monosulfide
SO2
S
H
H
Bent
Carbon dioxide
O C O
CO2
O
C
Linear
geometry
O
O C O
Ammonia
..
..
NH3
N
HH H
N
H
H
H
Trigonal
Pyramidal
geometry
N
H
107o
H
H
Hydrogen monochloride
H Cl
HCl
d(+)
d(-)
HCl(g) + H2O(l)  HCl(aq)
hydrogen
chloride
Polar molecule
water
hydrochloric
acid
Trichloromethane
d(+)
H
Cl C Cl
Cl
CHCl3
H
C
Cl
109.5o
Cl
Cl
Tetrahedral geometry
H
Cl C Cl
Cl
d(-)
Polar molecule
Urea
NOT “di-urea”
H
H
N
O C
N
H
H
CO(NH2)2
Urea – The first organic compound to be synthesized (Wohler, 1828).
Propane
H H H
HC C CH
H H H
C 3H 8
H
H
C
H
H
C
H
C
H
H
H
Butane
H H H H
HC C C CH
H H H H
H H H
H-C-C-C-C-H
H H H
H
C4H10
H
H
C
H
H
H
C
H
H
C
H
H
C
H
H
Nitrogen triiodide
..
N
I
I
I
NI3
N
I
107o
I
I
Trigonal
Pyramidal
geometry
Video clip:
(slow motion)
detonation of NI3
Supplies







15 black
8 green
1 yellow
4 blue
4 red
42 hydrogen
67 bonds
(carbon)
(chlorine and iodine)
(sulfur)
(oxygen)
(nitrogen)
(hydrogen)
(bonds)
C
Cl
S
I
Cl
Cl C Cl
Cl
H
HCH
H
CCl4
CH4
HC CH
C2H2
H Cl
HCl
O N
H
O C O
CO2
H
Cl C Cl
Cl
CHCl3
S
H H
SH2
H H H H
HC C C CH
H H H H
N
H HH
H H H
HC C CH
H H H
N
I
I
I
Decomposition of Nitrogen Triiodide