Maxperson
Morkus from Orkus
Usually I agree with your positions. In this case I present a possible basis for differences between the prime material and elemental planes.
The prime material has all four or five (in my personal model) elements. This mixing could if you wanted it to, be the basis for an entirely different set of rules around atomic theory in a game world.
2c
KB
For sure you could play it that way, but Gygax wrote the the elemental planes were the building blocks for the others. That sounds as small as it gets, which to me would include the atoms, molecules and elements. Especially when you consider that in 1e the elemental plane of earth has all of the gems, minerals and metals of the prime planes in it as native sources to find. Lastly, I found this gem in the 1e Manual of the Planes, "Toward the positive material plane, the water becomes warmer and more agitated until cohesiveness between water molecules breaks down and the plane of quasi-elemental steam is reached." It doesn't get clearer than that. Atoms and molecules exist on the elemental planes, just as they do on the prime planes.