# How to Make a 3-D Bohr Model

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In your introductory chemistry classes you will have to become familiar with a number of the early models of atoms, which represent scientists' early concepts of the structure of atoms. One of these models is the Bohr model, in which atoms consist of a positively charged nucleus surrounded by rings of electrons that orbit the nucleus in a system similar to the solar system. One of the best ways to learn about atomic models is to create them yourself, which you can easily do with styrofoam balls and pipe cleaners.

Look at a periodic table to determine the number of protons, neutrons and electrons in the atom that you wish to model. The bigger number on the periodic table for a particular atom is called the atomic mass and is equal to the sum of the number of protons and neutrons. The smaller number is equal to the number of electrons. Therefore, for beryllium, which has the numbers "4" and "9.01218," there must be four protons, four electrons and five neutrons (9 - 4 = 5).

Separate the larger styrofoam balls from the smaller ones. Paint four of the larger styrofoam balls in one color and five of them in another color. Allow them to dry.

Paint four of the smaller styrofoam balls in a third color and allow them to dry.

Connect the styrofoam balls in Step 2, which represent protons and neutrons, to each other in a cluster, using toothpicks.

Create two electron orbits with pipe cleaners. Each orbit should consist of a circle with two of the smaller styrofoam balls from Step 3, representing electrons, strung on it on opposite ends.

Place the electron orbits around the balls representing protons and neutrons. Connect the electrons to the proton and neutron ball with toothpicks in order to keep the whole model together. Cement the toothpick connections with glue, if necessary.

#### Things You'll Need

• Styrofoam balls (two different sizes)
• Paint (three colors)
• Pipe cleaners
• Toothpicks
• Glue (optional)

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