Atomic Models

WHAT TO DO

1. Pour enough of the small candies into the bowl to cover the bottom with one layer of candy. Each small candy represents one small atom. Do you see any patterns?


2. Gently shake the bowl from side to side and watch how the “atoms” move. Keep shaking until all of the atoms line up in straight lines. Do any of the rows go all the way from one side of the bowl to the other? What happens at the edges? Are there any gaps or cracks in the patterns you see?


3. Add the larger candies—approximately ¼ the number of small candies. Each large candy represents one large atom. Use your hands to mix up the balls and distribute the larger ones throughout. Again, gently shake the mixture back and forth and watch what happens to the atoms. Can you get them to line up again? Where do the large atoms go? Do you get different outcomes depending on how hard to shake?


4. Try more things! What happens if you add even more of the larger candies, or just a few? What if you add enough small candies to have more than one layer? What if you have lots of large candies and only a few small ones? What if you make a nice clear arrangement with gentle shaking and then shake harder? Or dump in all the candies at once and don’t shake at all? Or mix three different sizes, or two candies of the same size but different colors? Just like there are lots of different sizes and shapes and mixtures for round candies, there are lots of different ways that atoms can be mixed, with lots of different possibilities for what happens.

Cleanup:

You can munch on your candy or reuse the ball bearings for another purpose.

WHAT’S HAPPENING?

Everything around us is made of tiny building blocks called atoms – so tiny a powerful microscope is needed to see them. Scientists create bigger models of things we can’t see to help us understand how those things work. The different candies you used in this activity represent the atoms that make up all materials, and the model you made actually shows some of the same patterns and structures that you would see with a microscope.

Just as you added energy by gently shaking the bowl, materials scientists add energy (heat) to atoms to make them line up into an orderly structure. This is how atoms are arranged in a section of a typical metal. You may have noticed some boundaries where the candies on either side of the bowl line up in different directions. These boundaries are the edges between different crystals in the metal—defects in the structure where the material loses energy.

When you added the larger candies, you created a mixture similar to an alloy, a combination of metals that contains atoms of different sizes. The larger atoms break up the regular structure of the smaller atoms and the boundaries between crystals. These different arrangements of atoms can lead to some very different behaviors of the materials at a large scale.

SO WHAT?

Crystals can have atoms arranged in a very ordered structure, like the balls that were originally resting at the bottom of the bowl. This is called a crystalline structure. Or the arrangement can be disordered due to defects in the pattern or different types of atoms. This is called an amorphous structure. Defects in crystals aren’t necessarily a bad thing—they actually determine how different materials act or behave in our daily lives. For example, a baseball bat made with an amorphous metal is stronger and transfers more energy back to the ball because of how the atoms are arranged, but it is more costly than a standard bat. And stainless steel, which is made of disordered crystals, is a poor conductor of electricity while pure copper and pure silver, made of more ordered crystals, are much better conductors of electricity.

Scientists observe the atomic crystal structure of materials to determine how the materials will behave in the world. They can look at materials up close—even at the atomic level—using a high-resolution electron microscope. However, using this technology is very expensive and takes a long time compared to using other techniques. This technology can also be dangerous; it uses a very high voltage and emits X-rays, so they are built with many safeguards in place.

Scientists In Action For scientists Nasim Alem and Ritesh Uppuluri, microscopes gave them their first peek into a world that’s too small to see with our eyes. What can they discover by looking at tiny patterns of atoms?

For Teachers

The information below may not include every area that this activity can be linked to NGSS concepts.

Performance Expectations

• 2-PS1-3: Make observations to construct an evidence-based account of how an object made of a small set of pieces can be disassembled and made into a new object.


• 5-PS1-4: Conduct an investigation to determine whether the mixing of two or more substances results in new substances.


• MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures.

Disciplinary Core Ideas:

PS1.A: Structure and Properties of Matter

2nd Grade

• A great variety of objects can be built up from a small set of pieces.

5th Grade

• Matter of any type can be subdivided into particles that are too small to see, but even then the matter still exists and can be detected by other means. A model showing that gases are made from matter particles that are too small to see and are moving freely around in space can explain many observations, including the inflation and shape of a balloon and the effects of air on larger particles or objects.

Middle School

• Substances are made from different types of atoms, which combine with one another in various ways. Atoms form molecules that range in size from two to thousands of atoms.


• Solids may be formed from molecules, or they may be extended structures with repeating subunits (e.g., crystals)

PS1.B: Chemical Reactions

5th Grade

• When two or more different substances are mixed, a new substance with different properties may be formed.

Please click on the PDF below for a more detailed description of how this activity ties to NGSS

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