## Reflection: Rigor Atom Model Demonstration - Section 4: Student Activity

I point out that in science we use models to represent the physical world we are studying. Often these models have limitations and we must understand these limitations to fully understand the principles involved.

The atomic model often used in classrooms is the planetary model, developed by Neils Bohr in 1909. (I have a picture of Bohr hanging on the front of my classroom, see History of Science lesson.)

While this model provides a good understanding of the concepts it has its limitations. First electrons don't travel in nice neat paths, but rather in a cloud around the nucleus. Second, the electrons are depicted as being almost the same size as the protons and neutrons. I explain to students that they should think of a bowling ball as the size of the proton and a flake of dust as the electron. Finally the electrons are much too close to the nucleus. At the scale size of a bowling ball and a flake of dust the electron should be placed almost eleven miles away.

While it is important to use models, understanding their limitations and pointing them out to students provides a richer understanding of science.

Limitations of scientific models
Rigor: Limitations of scientific models

# Atom Model Demonstration

Unit 4: Atomic Structure
Lesson 1 of 5

## Big Idea: Using a large hulla-hoop atom model the teacher will demonstrate atomic structure, number, and mass.

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175 minutes

### Sean Gillette

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