How to Build a Model of an Calcium Atom

Updated February 21, 2017

A popular project for chemistry classes is to make a model of an atom. The calcium atom has a relatively large number of protons, neutrons and electrons when compared to other types of atom, but you can still make a three-dimensional model of an atom of this element. Most of the items needed can be found in any craft store. Be sure that the items you choose to represent the protons and neutrons are much larger than those you use for your electrons.

Set aside 20 large marshmallows (or cotton balls) for the protons. Use a marker to colour all of these the same colour. In the Periodic table, calcium has an atomic number of 20 and an atomic weight of 40.

Subtract the atomic number (20) from the atomic weight (40) to get the number of neutrons to make (20). Colour 20 more large marshmallows or cotton balls a different colour from that you used in step 1.

Glue all of the coloured marshmallows or cotton balls together into a large ball. This will be the nucleus of the atom.

Cut two pieces of floral wire about 3 inches long. Cut another eight pieces about 4 inches long. Eight more pieces should be cut to 5 inches long and two need to be 6 inches long.

Skewer 20 mini marshmallows or jelly beans onto the end of all of the cut pieces of floral wire. You can also use glue to attach these. These mini-marshmallows are the electrons, and the floral wire of differing sizes represent the different orbitals. Floral wires of matching size are the same orbital.

Put a dab of glue onto the other end of the floral wire and push this into the large marshmallow nucleus. Be sure that the floral wires of similar lengths hold the marshmallows at the same distance from the nucleus. For instance, the two shortest wires will hold the mini-marshmallow electrons the same distance from the nucleus.


Toothpicks or wooden skewers can be used instead of floral wire.

Things You'll Need

  • Floral wire
  • Scissors
  • Glue
  • Large marshmallows (or large cotton balls)
  • Markers
  • Mini marshmallows or jelly beans
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