Adapted from: Schwaner, T.D., Petty, J. T., Schwaner, L.A.
(1994). Modeling Atoms and Molecules: A New Lesson for Upper
Elementary and Middle School Students, The American Biology Teacher,
56:8, pp. 488-491.
- University of Virginia
- Physics Department
Cloud Model of
the Atom I
A Physical Science Activity
2003 Virginia SOLs
- describe the arrangement of electrons in atoms according to their energy
- describe the structure of a water molecule.
This activity offers a three dimensional model of atoms based on
the cloud or quantum model. Students use B.B.'s to represent
electrons inside of balloon electron clouds. The activity can be
conducted as a student-centered activity where students work in small
groups, or the teacher can lead the class through the steps with
discussion. There are shortcomings within the model in that no
nucleus is represented and the student must imagine its presence. Of
particular value in the model of the more complex atom, oxygen,
however, is the arrangement of electrons into two distinct orbital
levels as represented by one balloon inside the other.
To print out the Student Copy only,
- 1 12-inch and 1 5- inch balloon of identical color (described
as "red" in the procedure)
- 2 5-inch balloons of identical color but of a different color
than the first set of balloons (described as "green" in the
- 10 BB's
- Place 1 BB in each of the small green balloons. Carefully
(without inhaling the B.B.) blow up each green balloon so it is
approximately the size of a hen's egg. Tie each off. Each now
represents the simplest possible atom, hydrogen. Strictly
speaking, the model of hydrogen is incomplete as no nucleus is
present, but one can imagine the presence of a nucleus at the
center of the balloon. Rotate one of the balloons so the BB moves
around on the inner wall. Then, add energy to the atom model by
spinning the balloon faster. As in a real atom, the electron
reflects the added energy. In a real atom, the electron will
"jump" to a new energy level. In the model, the electron simply
- For a more complex atom, place 2 BB's in the small red
balloon. Place 6 BB's in the large red balloon. Insert the
uninflated small red balloon into the large red balloon. Hold the
ends of the balloons together and carefully inflate the small red
balloon while it remains inside the large balloon. Only inflate it
enough so the walls stand out away from the B.B.'s. Tie it off.
Next, inflate the large red balloon while continuing to push the
small red balloon farther inside. Continue to inflate the large
red balloon until it is significantly larger than the small
balloon now inside. Tie off the large balloon. This atom now
contains 8 electrons and represents oxygen. Point out to the
students that the 8 electrons are grouped as 2 in the inner
orbital (balloon) and 6 in the outer. Though this model is still
deficient in that atoms are not distributed into orbitals, it
still demonstrates that they occupy varying distances from the
- The oxygen atomic model and hydrogen atomic models can further
be combined to represent a water molecule that would demonstrate
the stability of an octet of electrons in the outer valence levels
of atoms involved in chemical bonds.
- Students research historical development of atomic models.
- Students research chemical properties of an element.
Students with Special Needs
This activity requires fine motor skills if it is to be conducted as a student-centered
activity. It will work well as a teacher-centered demonstration if students
are not able to manipulate the materials comfortably.
Click here for further
information on laboratories with students with special needs.
- Students describe how to construct a model of atoms different
than those in the activity using the materials included in the
- Students build atomic models using materials they choose.