Final answer:
Ernest Rutherford determined that atoms could break apart into smaller atoms, releasing energy.
Step-by-step explanation:
Ernest Rutherford is the scientist who determined that atoms could break apart into smaller atoms, releasing energy in the process. Rutherford performed a series of experiments using a beam of high-speed, positively charged alpha particles that were produced by the radioactive decay of radium. He aimed the beam of alpha particles at a thin piece of gold foil and examined the resultant scattering, which led him to revise the model of the atom.