This document appears to list scientists and the years they proposed theories or conducted experiments related to atomic structure and subatomic particles. It mentions Leucippo and Democritus proposing an early model of matter being made of indivisible particles, Dalton proposing atoms as the basic unit of matter, Thomson discovering the electron, Rutherford proposing a nuclear model of the atom with electrons orbiting a nucleus, Chadwick discovering the neutron, Bohr creating an early quantum mechanical model of the hydrogen atom, Lewis developing the covalent bond theory of chemical combination, and Schrödinger proposing wave mechanics and the wave nature of subatomic particles.