Abstract
By using differently sized foam polystyrene balls with lead weights, a particle model expressing the weight and size of atoms was created. The size of each ball was chosen so that its radius would be approximately 5×10^8 times as large as the radius of a real atom. As for the weight, by removing the inner part of the foam polystyrene near the centre of the ball or by putting a small piece of lead in the ball, each ball was made to be 6×10^<23> times as heavy as a real atom, so that its weight measured in grams was coincident with the atomic mass. The model we developed was used in junior high school science classes, and the responses from the students were positive.
