Structure of the Atom. Lecture 1. Early Theories of Matter. Democritus (460-370 B.C.) – Greek Philosopher Proposed that matter was not infinitely divisible Matter was made up of tiny individual particles called atomos Atomos could not be created, destroyed, or further divided
Rutherford concluded that the atom was composed of a tiny, dense region, he called the nucleus, which contained all of an atom’s positive charge and mass surrounded by mostly empty space containing the electrons.
James Chadwick (1932) showed that the nucleus also contained another subatomic particle, a neutral particle he called the neutron.