Lab
#8 Three-dimensional Models of Covalent Molecules
Objective:
Build three-dimensional models of some simple covalent molecules. Predict their shapes and polarities from knowledge
of bonds and molecule polarity rules.
Observations:
1.
In the molecular model building kit, the black balls have 4 holes. These represent carbon.
2.
In the molecular model building kit, the yellow balls have 1 hole. These represent hydrogen.
3.
In the molecular model building kit, the green balls have 1 hole. These represent a halogen.
4.
In the molecular model building kit, the orange balls have 1 hole. These represent a halogen.
5.
In the molecular model building kit, the purple balls have 1 hole. These represent a halogen.
6.
In the molecular model building kit, the blue balls have 3 hole. These represent nitrogen.
7. In the molecular model building kit, there are wooden sticks which represent bonds.
8.
In the molecular model building kit, there are spring which represent double or triple bonds.
Data:
Molecular Model Data
Name Formula Structural Shape Molecular Polarity
Representation (Polar or
Non Polar)
Hydrogen H2
Linear
Non-polar
Water H2O
Bent
Polar
Methane CH4
Tetrahedron
Non-polar
Chlorine Cl2 Linear
Non-polar
Ammonia NH3
Triangular Pyramidal Polar
Hydrogen
Fluoride HF
Linear
Polar
Ethyne C2H2
Linear
Non-polar
Dichloromethane CH2Cl2
Tetrahedron
Polar
Nitrogen
N2
Linear
Non-polar
Carbon Dioxide
CO2 Linear
Non-polar
Methanol
CH3OH
Tetrahedron
Polar
Hydrogen Peroxide H2O2 Bent
Polar
Oxygen
O2 Linear
Non-polar
Hydrogen Sulfide H2S
Bent
Polar
Calculations:
N/A
Conclusions:
1. A molecule can be non-polar with
polar bonds due to symmetry.
2. Triangular pyramidals and bent
molecules are always polar.
3. The holes in the balls represent the number of electrons
needed by the molecule to obtain an octet.
4. There is no shape that is always
non-polar.
5. Diatomic molecules are always
linear and non-polar.
Questions:
1. Which molecules were non-polar because all bonds were
non-polar?
The molecules that were non-polar due to their non-polar bonds were hydrogen, chlorine, nitrogen, and
oxygen.
2. Which molecules had polar covalent bonds but were non-polar because of symmetry?
The molecules that were no-polar due to symmetry were methane, ethyne, and carbon dioxide.
3. Which two shapes appeared to produce polar molecules every time?
Bent molecules and triangular pyramidals are always polar.
4. Name two types of substances that do not contain molecules with covalent bonds.
The two type substances that do not contain molecules with covalent bonds are metallic compounds, and
ionic compounds.
