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. 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

3. 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 :

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 C2H6 C = 1s22s22p2 ball-and-stick
Lewis dot notation
C2H6
molecular formula
space-filling molecule

8. Ethane H H H C C H H H C2H4 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. Hydrogen monochlorideCl H H Cl Cl
HCl
d(+)
d(-)
HCl(g) + H2O(l)  HCl(aq)
hydrogen
chloride
water
hydrochloric
acid
Polar molecule

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

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

16. Propane H H H H H H C C C H C C C H H H H H H H H H
C3H8

17. 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

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

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

20. C Cl I S N O H Cl H Cl C Cl H C H O C O Cl H S H H H H C C H Cl C Cl

21. 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

22. Decomposition of Nitrogen Triiodide