University of Virginia
Physics Department

Cloud Model of the Atom II

A Physical Science Activity

Student Activity

Materials

• Large round balloon (12 inch inflated)
• Small round balloon (water balloon size)
• 4 mm round B.B.'s
• 2 mm round B.B.'s (or small, lightweight beads)

Procedure

1. Select an atom between 1 and 20 from the periodic table that you wish to build. Determine the number of protons, neutrons, and electrons in the atom.
2. Retrieve the appropriate number of 4-mm B.B.'s to represent the protons and neutrons in the nucleus. Place these B.B.'s in the small round balloon.
3. Next place the appropriate number of small (2 mm) B.B.'s into the larger balloon.
4. Insert the small balloon into the large balloon and hold the ends together.
5. Carefully inflate the small balloon while it is in the larger balloon. It should only be slightly inflated such that its walls stand out and it retains a round shape. Tie off the small balloon.
6. Inflate the large balloon while forcing the small one farther in. Continue to blow up the large balloon until it is fully inflated and much larger. Tie it off.
7. Write the symbol of the element, its atomic number and atomic mass on the outside of the balloon.

Data Sheet

 1. Which atom did you model? Write its name and symbol in the space below.     2. How many protons, neutrons, and electrons are in your model? Number of Protons: _____________________ Number of Neutrons: _____________________ Number of Electrons: _____________________   3. What object(s) represent the protons, neutrons, and electrons in your model? Protons: _______________________ Neutrons: _______________________ Electrons: ______________________   4. Which part of your model has the greatest mass? ____________________________ (This part of the model with the greatest mass represents the nucleus of the atom. In a real atom, it is the heaviest part and has the greatest density too.)   5. Where are the electrons in your model? __________________________________ (In a real atom, the electrons are arranged at different levels from the nucleus, but are far from the nucleus. Most of an atom is empty space! In the model, the "empty space" is not really empty but occupied by air.)