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The Atomic DashboardTM
Worksheet: Atomic and Molecular Models
Name _______________________Period _________ Date _______________
In this assignment, you will use the Atomic Dashboard’s interactive periodic table to learn how
atoms and molecules are represented as models. Computer generated 3D atomic and
molecular models, like 2D symbolic and mathematical models, are part of the language of
chemistry. Chemistry takes place at the nanoscale level -- a level that cannot be observed with
the naked eye, nor in most cases, even with a microscope. As a result, the ability to understand
atomic and molecular models and what they represent is essential to learning chemistry.
Procedure:
1. Read the instructions and questions below to preview your assignment. !
2. Open the Atomic Dashboard. !
3. Click on the top left box labeled “H” for the element hydrogen. Hydrogen’s
Properties box will open. At the top center of the Properties box, examine the 2D
model of a hydrogen atom. The model is called a Bohr diagram or electron shell
diagram. !
Observations:
1. Describe what information you think that the Bohr diagram of hydrogen is representing.
A Bohr diagram is a simplified model of an atom -- its nucleus and electrons that surround the
nucleus. In the case of hydrogen, one electron is shown in a circular orbit around its nucleus. A
Bohr model is also sometimes called a planetary model because, like the sun and surrounding
planets, the electrons orbit the nucleus much like planets orbiting the sun. The attractive
gravitational force in the solar system and the attractive force between the positively charged
nucleus and the negatively charged electrons in the atom are represented mathematically in a
similar manner.
4. In the Properties Box, under “Atomic Properties,” click on 1s1 to load a 3D atomic
orbital model of hydrogen. In the model window, use the
examine this model of a hydrogen atom. !
5. Open the “Glossary” (“Help” menu). !
6. Click on and read the definition of “atomic orbital.” !
and
controls to
2. Describe how an orbit (in the Bohr model) is different from an orbital (in the Schrödinger
Model).
Bohr orbit = distinct circular path.
Schrödinger orbital = a cloud of probability.
7. In the Periodic Table, click the top left box labeled “He” for the element helium. !
8. Open the Glossary (Help menu) and click on and read the definition of “atom.” !
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3. Helium is one of the noble gases. What does that mean according to the definition that
you just read?
That an atom of helium is also a molecule of helium because atoms of helium can exist
independently in nature i.e. they do not need to be bonded to other atoms to be stable.
.
9. In helium’s Properties box, click on 1s2 to load a 3D atomic orbital model of helium.
In the model window, use the
and
controls to examine this model of a
helium atom. !
10. In the lower left of helium’s Properties box, use the “Select an Element Model”
dropdown menu to select “Helium (gas)”. !
11. For a moment, observe the model of helium molecules as a gas in the Model
Window. Then click the “Stop Simulation” at the bottom of the Model Window. !
4. In the gas model of helium, how are helium atoms/molecules represented? Why do you
think this model represents helium differently from the orbital model? Is that a good or a
bad thing?
In the gas model, each helium atom’s orbital cloud of electrons is represented as a solid
sphere.
Solid sphere models more practically and effectively illustrate helium’s properties as a gas.
Neither -- models are meant to simplify our world and facilitate understanding. As George E.
P. Box, a statistics professor at the University of Wisconsin-Madison once said, "Essentially,
all models are wrong, but some are useful."
12. Click on the element box in the second row of the periodic table labeled “O’ for
oxygen. !
13. In the lower left of oxygen’s Properties box, use the “Select an Element Model”
dropdown menu to select “Pure Element” >> “Oxygen (molecule)”. In the Model
Window, you should see what’s called a ball and stick model of an oxygen
molecule. !
5. Describe what you think the ball and stick model of the oxygen molecule represents.
The spheres: two atoms of oxygen The sticks: two bonds/forces between the oxygen
atoms that attract the atoms together to form a molecule of oxygen
14. At the bottom of the Model Window, use the dropdown menus to change the “Model
Type” to “Bond Pairs, “ and “Model Options” >> “Lone Pairs” >> “Show Lone
Pairs.” !
15. Compare the 3D model of the oxygen molecule in the Model Window to the Bohr
diagram of the oxygen atom at the top of its Properties box. !
6. How many oxygen atoms are represented in the model in the Model Window? What do
the small red spheres in the model in the Model Window represent?
Two oxygen atoms.
The small spheres represent each of the two atoms’ outer shell/orbit electrons.
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