What major conclusion was drawn from the Geiger-Marsden experiment regarding the structure of the atom?

The Geiger-Marsden experiment, also known as the gold foil experiment, provided significant insight into the structure of the atom. Through this experiment, alpha particles were fired at a thin foil of gold. Most of the alpha particles passed through the foil without any deflection, while a small fraction were deflected at large angles, and a very few even bounced back.

From this behavior, one major conclusion was drawn: the atom contains mostly empty space. The fact that so many alpha particles passed through the gold foil indicates that the majority of the atom is not dense; instead, it is primarily composed of empty space. This was a revolutionary conclusion that contradicted the prevailing model of the atom at the time, which suggested a more solid structure.

The results also indicated that the positive charge and most of the atom's mass are concentrated in a small central region, which we now know as the nucleus. However, that specific finding about the central concentration of mass and charge does not change the conclusion about the overall structure indicating that the atom is predominantly empty space. Thus, this conclusion is fundamental to our understanding of atomic structure as defined in modern physics.