University of Virginia
Physics Department

## Atomic Model Construction

A Physical Science Activity

2003 Virginia SOLs

• PS.1
• PS.3
• PS.4

Objectives

Students will

• calculate numbers of protons, neutrons, and electrons in an atom from data presented on the periodic table;
• construct models of atoms that demonstrate understanding of electron arrangements according to the Bohr model.

Motivation for Learning

Computer Demonstration: Atomic Modeling

To give students an idea of the shapes and scales of atoms, link to http://www.colorado.edu/physics/2000/applets/a2.html for a fully interactive periodic table. This table allows teachers and students to explore moving atomic models of each of the first 36 elements. Click on any element's chemical symbol to analyze it. Zoom in on the nucleus to show the closely compacted structure and note how far the electrons orbit from it. The table also provides electron shell configurations and electron potential energies. Remind students of the limitations of the modeling system: electrons follow three-dimensional spherical paths, not simple cirlcular ones as depicted. Also remind them that protons and neutrons are around 2000 times more massive than electrons.

Background Information

Making models of atoms is an activity many teachers use with their students. It emphasizes to the students that atoms are not two-dimensional, fixed entities. Students can make the models in school or at home, and they can use a wide variety of objects-only a few are suggested here. The models constructed have shortcomings in that they are stagnant, and the electrons may appear to be at specified, rather than most probable, distances from the nucleus.

### Student Activity

Materials

• Periodic Tables
• Rings in various sizes (could be wire, wooden, embroidery hoops, etc.)
• Styrofoam balls
• Small objects such as pompoms, jelly beans, gum drops, mini marshmallows
• Optional - fishing line or thin string

Procedure

1. Have students select an atom above element number 11 (sodium) to model. (This assures the element will have at least three energy levels).
2. The student then finds the number of protons, neutrons and electrons in the chosen atom.
3. Student constructs a three dimensional model of the atom using the styrofoam ball as the nucleus with the appropriate number of small objects (pompoms, for example) attached to it to represent protons and neutrons. The electrons are attached to the rings in the configuration matching the electron arrangement of the atom as calculated by the student.
4. The models are fun for the students to display within the classroom and they will serve as reminders of the atomic structure as more complex issues are encountered.
5. If the students wish to make mobiles out of their creations, hang the models from the ceiling or other support with the fishing line or string.

 Figure 1: A model of a chlorine atom using "Play Dough" as protons (red), neutrons (yellow), and electrons (blue) attached to metal craft rings (12 in., 5 in., and 3 in.)

 Figure 2: Atomic model of a sodium atom using pipe cleaners, ¼ in. pom poms (protons are red and neutrons are white), and small beads as electrons.

 Figure 3: Atomic model of an aluminum atom using ¼ in. pom poms as protons (white) and neutrons (black), 1/8 in. pom poms as electrons, and craft wire.

Extensions

Students can explore the interactive online periodic table at http://www.colorado.edu/physics/2000/applets/a2.html. Each student compares the model he/she has created in the student activity with the online version of the atom and notes the successes and deficiencies of each model.

Students with Special Needs

This may be a difficult activity for students who are unable to manipulate small objects. Rather than working independently, however, students could work with partners or within small groups.

Click here for further information on laboratories with students with special needs.

Assessment

1. Accuracy of model.
2. Students describe structure of another atom.
3. Students critique other students' models for accuracy.