Rutherford model

Meaning: Rutherford's model, based on the gold foil experiment of Geiger and Marsden, pictures the atom as a tiny, dense, positively charged nucleus holding nearly all the mass, with electrons moving around it in mostly empty space. Alpha particles (He²⁺) were fired at thin gold foil. Most passed nearly straight through, so the atom is mostly empty space. A small fraction deflected at large angles and a very few rebounded almost backward, so the positive charge sits in a small core that repels the positive alpha particles. This replaced Thomson's plum pudding model, which spread positive charge throughout the atom.

On the MCAT: Passages describe a scattering experiment and ask what an observation implies. Straight passage means empty space; large deflection means a positive, concentrated nucleus; rare backscatter means the nucleus is very small compared with the atom. A nucleus of higher charge (larger Z) deflects alpha particles more strongly.

Common confusion: Rutherford's model does not include quantized energy levels or explain line spectra; those come from Bohr. In classical physics, orbiting electrons would radiate energy and spiral into the nucleus, a flaw that Bohr's quantized orbits addressed.