HANDOUT
MODELS OF MOLECULES
The properties of a substance are dependent on the number and kinds of atoms present in a
molecule and their geometric arrangement. The detailed information required to build accurate models
has been obtained by complicated experiments. We can, however, learn a lot about molecules by
looking at models.
When constructing models, we must do so in accordance with all the laws and rules of electron
behavior. The octet rule is usually obeyed and electron pairs repel one another and seek to be as far
away from one another as possible. By studying the arrangements of the bonds and by knowing the type
of bond formed we can also learn about the polarity of a molecule. It must be remembered that we live
in a three dimensional world, and that the shapes of molecules are also three dimensional.
In using the molecular model kits, we will use the following conventions:
Black = Carbon
Yellow = Hydrogen
Orange = Bromine
Red = Oxygen
Green = Chlorine
Blue = Nitrogen
Purple = Iodine
PROCEDURE:
A. Methane, CH4
1.
Draw the Lewis dot structure for methane.
2.
Construct the model using carbon as the central atom surrounded by the four hydrogen atoms.
The hydrogen atoms are placed as far apart from one another as possible.
3.
Is this C-H bond polar or nonpolar?
4.
Looking carefully at the molecular model, is the molecule polar or nonpolar?
5.
Is the angle formed between the hydrogens greater than 90? Is the angle greater than
Revised 3\93
120?
2
B. Water, H2O
1.
Draw the Lewis Dot structure for Water.
2.
Make the model of water.
3.
Is the O-H bond polar or nonpolar?
4.
Is the molecule polar?
5.
Are there any nonbonding pairs of electrons? If so, how many?
C. Carbon Tetrachloride, CCl4
1.
Draw the Lewis Dot diagram.
2.
Is the C-Cl bond polar?
3.
Is this molecule polar?
4.
What type of bond is present in this compound?
D. Nitrogen, N2
1.
Draw the Lewis Dot diagram for Nitrogen.
2.
Construct the model of Nitrogen.
3.
Is this a polar or nonpolar molecule?
4.
Are there any unshared pairs of electrons present? If so, how many?
3
For Additional Practice:
Draw Lewis structures for these covalent molecules, which contain only single bonds.
H2S
PH3
C2H6
C8H18
Draw Lewis structures for these molecules which contain double or triple bonds.
CO2
C2H4
N2
SO3
Classify the bonding in each compound below as ionic or covalent.
H2O
H2SO4
NaBr
CaCl2
MgO
NH3
F2
CF4
4
Name the following binary compounds:
1.
KI
11.
SnO
2.
CaF2
12.
CaCl2
3.
MgO
13.
FeS
4.
AsCl3
14.
NaH
5.
HgCl2
15.
CdS
6.
NaCl
16.
CuCl
7.
Rb2S
17.
CaH2
8.
HI
18.
Na2O
9.
SnCl2
19.
MgBr2
10.
Fe2O3
20.
Ag2S
Name the following ternary compounds:
1.
ZnSO4
7.
FeSO4
2.
AgNO3
8.
CuCO3
3.
CaCO3
9.
Fe(OH)3
4.
Na3PO4
10.
Ca3(PO4)2
5.
AlPO4
11.
Hg(NO3)2
6.
Al(NO3)3
12.
CdCO3
5
Give the formula for the following:
1.
Carbon Monoxide
17.
Boron Triiodide
2.
Lead (II) Acetate
18.
Magnesium Nitrate
3.
Copper (I) Sulfide
19.
Silver Oxide
4.
Ammonium Hydroxide
20.
Cesium Chloride
5.
Sulfuric Acid
21.
Sodium Sulfide
6.
Potassium Oxide
22.
Calcium Hydride
7.
Beryllium Bromide
23.
Lithium Nitrate
8.
Barium Fluoride
24.
Ammonium Iodide
9.
Zinc (II) Acetate
25.
Calcium Oxide
10.
Nitric Acid
26.
Silver (I) Nitrate
11.
Sodium Hydroxide
27.
Arsenic Trichloride
12.
Potassium Dichromate
28.
Copper (I) Cyanide
13.
Nickel (II) Sulfate
29.
Lithium Hydroxide
14.
Dinitrogen Monoxide
30.
Iron (III) Acetate
15.
Nitrogen Dioxide
31.
Silver (I) Dichromate
16.
Carbon Tetrabromide
32.
Carbon Disulfide