Molecular Model Photo Gallery Back to Models Index Excerpt from The Packing of Marbles in Balloons      In an effort to determine how the mutually attracting particles in the nucleus of an atom might arrange themselves, an analogy was devised, using marbles in balloons. By using the appropriately sized marbles in an appropriate spherical balloon, the inflated surface develops flat faces with rounded corners, without nubbling by protruding marbles, but with sufficient surface tension to force the mass of marbles, when agitated, into a close-packed arrangement.      The balloons containing the marbles were inflated with water and agitated, then the water adjusted to the correct degree of inflation. By knowing the weight of the marbles, the balloon, and the water, the percent void (the volume-percent of water in the balloon) was calculated. By freezing the water-filled balloon it is possible to peel off the balloon and study the marbles on the surface, and then by melting off the surface marbles, to observe the structure of the marbles in the core.