Atomic Model

Nuclear Science Merit Badge requirement 2b states:  

Choose an element from the periodic table. Construct 3-D models for the atoms of three isotopes of this element, showing neutrons, protons, and electrons. Use the three models to explain the difference between atomic number and mass number and the difference between the atom and nuclear and quark structures of isotopes.

For this project, my son chose carbon and made models of the ¹²C, ¹³C and ¹⁴C isotopes.  ¹²C has 6 protons, 6 neutrons and 6 electrons.  ¹³C is the same except it has 7 neutrons.  ¹⁴C is also the same, except it has 8 neutrons.  

For this project, you need styrofoam balls, toothpicks, bamboo skewers, 3 colors of paint and paint brushes.  

Put a toothpick in each styrofoam ball to make it easier to paint.  Use an old box or piece of styrofoam to hold the painted balls.  It was hard to puncture the box with the toothpick, so I drilled a bunch of holes with a 1/16" bit.  

Once all the balls are painted and dry.  Put together your isotopes.  For this model, the protons are red, neutrons blue, and electrons yellow.  You can use whatever colors you like.  Stick the protons and neutrons together with toothpicks to make the nucleus.  

Carbon atoms have 6 electrons in 2 orbitals.  2 are in the first inner orbital and 4 in the second outer orbital.   The bamboo skewers for the inner orbital were cut to 8" and the ones for the outer orbital were left at 12".  All of the blunt ends were sharpened with a pencil sharpener.

The last step was to mark the protons (red) with a "+" and the electrons were marked with a "-" using a Sharpie.  A label maker was used to mark them as ¹²C, ¹³C and ¹⁴C.  Fishing line was used to hang them from the ceiling in his room.  

You could also complete this requirement with marshmallows and toothpicks.  This would be more economical and much easier.  It would also be simple to scale this up to a troop level activity.  

The image below represents 3 isotopes of hydrogen.  From left to right are:  Protium ¹H, Deuterium ²H, and Tritium ³H.  The pink marshmallows represent protons.  Neutrons are white.  The small green marshmallows are electrons.  I made the plus and minus markings with a Sharpie since I'm not going to eat these.  If you wanted to have a troop activity where the Scouts would be able to consume their models afterwards, you could use edible gel pens.  You can find these in the baking aisle of the grocery store along with other cake decorating supplies.  You could use plain white marshmallows, but the colored ones are more fun if you can find them.