Purpose Construct Models of Various Simple Covalent Molecules Using a Model Building Kit

Student page

Purpose Construct models of various simple covalent molecules using a model building kit.

Materials

Molecular model kit

Student worksheet

Scientists have been diagramming the 3D arrangement of molecules since 1874 when J.H. van’t Hoff discovered this aspect of their structure. In this lab, you will use a kit to model the 3D structure of a number of molecules, including some of those van’t Hoff discussed. After building the models, draw them on your paper in their 3D representation. Draw e-dot diagrams for each molecule as well.

Pre-lab Questions

1. How do electrons behave during covalent bonding?

2. Examine the various atom models and note the number of holes in each. What do these holes represent?

3. What do the connectors between the spheres serve as in our model?

4. Chlorine has 17 electrons. But the electron dot diagram only has 7. Why?

5. How many electrons make up a bond?

6. What types of elements do we expect to bond together covalently?

Procedure

1. Follow along as your teacher builds H2 with you. Notice that the chart is already filled in for you.

2. Build the remaining molecules remembering these two rules:

a. All holes on each sphere must be filled.

i. Exception: Nitrogen usually has 4 holes, but you will use only 3.

b. Connectors cannot return to the same sphere.

3. Use appropriate available resources for help if needed.

FORMULA / ELECTRON – DOT / DRAW IN BONDS / DRAW MODEL
H2 / H ·· H / H ¾ H /
O2
N2
F2
H2O
NH3
CO2
HCl
HCN
CH4

Analysis

1. The first three molecules created are known as diatomic elements. What does this mean?

2. What is the main difference between H2, O2, and N2 based on your chart?

3. Is CH3 a stable covalent compound? Why or why not?

4. How do you know that oxygen only has two places for bonding with another atom?

5. Which of the following is not a covalent compound? Why?

a. CCl4

b. CH4

c. NH3

d. Al2O3