Final answer:
Rutherford's experiments led to the conclusion that an atom's positive charge is concentrated in a tiny, central nucleus.
Step-by-step explanation:
From his experiments, Rutherford concluded that the positive charge of an atom is concentrated in a tiny area at the center of the atom. This region, known as the nucleus, contains most of the atom's mass and positive charge, and is composed of protons and neutrons. The discovery undermined the then-prevailing plum pudding model, which assumed that positive charge was distributed evenly throughout the atom. Instead, Rutherford's model describes the atom as mostly empty space, with electrons orbiting a central, densely packed nucleus.