1. Molecular Models Activity
carbon tetrachloride
methane
water
ethane
ethyne
dihydrogen monosulfide
carbon dioxide
ammonia
hydrogen monochloride
trichloromethane
urea
propane
butane
nitrogen triiodide (video)
supplies

2. Bonding and Shape of Molecules
Number
of Bonds
Number of
Unshared Pairs
Covalent
Structure
Shape
Examples 2 3 4 1 2
-Be-
Linear
Trigonal planar
Tetrahedral
Pyramidal
Bent
BeCl2
BF3
CH4, SiCl4
NH3, PCl3
H2O, H2S, SCl2 B C N : O :

3. 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)
- no unpaired electrons (free radicals)
4) Check
- valence electrons match with Step 1
- all atoms (except H) have an octet;
if not, try multiple bonds
- any extra electrons?
Put on central atom

4. Carbon tetrachloride Cl Cl C Cl Cl Cl C CCl4 Tetrahedral geometry
Carbon tetrachloride – “carbon tet” had been used as dry cleaning solvent
because of its extreme non-polarity.

5. Methane H H C H H H C Tetrahedral geometry
Methane –The first member of the paraffin (alkane) hydrocarbons series.
a.k.a. (marsh gas, CH4).

6. Water
d(-) .. ..
SO2
Bent
geometry H O
d(+)
Polar molecule

7. Ethane H H H C C H H H C2H4 C = 1s22s22p2 ball-and-stick
Lewis dot notation
C2H4
molecular formula
space-filling molecule

8. Ethane H H H C C H H H C2H6 ball-and-stick Lewis dot notation
molecular formula
space-filling molecule

9. Ethyne H C C H C H C H H C C H C2H2 No octet 6 electrons = triple bond
each C “feels” 6 electrons H C C H C H C H
Stable octet
C2H2 H C C H
each C “feels” 7 carbons
Ethyne – a.k.a. “acetylene”

10. Dihydrogen monosulfide.. ..
SO2 H S
Bent

11. Carbon dioxide O C O O C O O C
Linear
geometry
CO2

12. Ammonia N
107o H .. .. N H N H N H H
NH3 H
Trigonal
Pyramidal
geometry

13. : : : : Amino Acids – Functional Groups NH21- R- COOH NH21- NH3 NH41+
Amine
Base Pair
Carboxylic Acid
NH21-
R- COOH
lose H+ H+
NH21-
NH3
NH41+ : N H : 1+ : 1- N N : H H H H H
amine
ammonia
ammonium ion

14. Hydrogen monochlorideCl H H Cl Cl
HCl
d(+)
d(-)
HCl(g) + H2O(l)  HCl(aq)
hydrogen
chloride
water
hydrochloric
acid
Polar molecule

15. Trichloromethane H H Cl C Cl Cl C Cl Cl Cl H C Cl d(+) CHCl3 d(-)
Tetrahedral geometry
Polar molecule

16. Urea H H H H N N O C O C N N H H H H CO(NH2)2 NOT “di-urea”
Urea – The first organic compound to be synthesized (Wohler, 1828).

17. Propane H H H H H H C C C H C C C H H H H H H H H H
C3H8

18. Butane H H H H H C C C C H H H H H H H H H H - C - C - C - C - H

19. Nitrogen triiodide N I I I .. N I NI3 Trigonal Pyramidal geometry
Video clip:
(slow motion)
detonation of NI3

20. Supplies 15 black (carbon) 8 green (chlorine and iodine)
1 yellow (sulfur)
4 blue (oxygen)
4 red (nitrogen)
42 hydrogen (hydrogen)
67 bonds (bonds)

21. C Cl I S N O H Cl H Cl C Cl H C H O C O Cl H S H H C C H H H Cl C Cl
CHCl3
HCl

22. H H H H H H H H C C C C H H C C C H H H H H H H H N N I I H H H I

23. Decomposition of Nitrogen Triiodide

25. Decomposition of Nitrogen Triiodide
Molecules store energy (chemical potential energy) in the bonds that hold them together. When the bonds are broken, energy is released.
2 NI3(s) N2(g) I2(g)

26. N H .. .. C H O .. H H .. O CH4, methane NH3, ammonia H2O, water O
lone pair
electrons O O
O3, ozone

27. The VSEPR Model .. .. .. The Shapes of Some Simple ABn Molecules O S O
Linear
Bent
Trigonal
planar
Trigonal
pyramidal
AB6 F P F S F Cl
Students often confuse electron-domain geometry with molecular geometry.
You must stress that the molecular geometry is a consequence of the electron domain geometry.
The best arrangement of a given number of electron domains is the one that minimizes the repulsions among them. F Xe
T-shaped
Square
planar
Trigonal
bipyramidal
Octahedral
Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 305