Matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. D.O.B - 460 BCE.
He deduced that all elements are composed of atoms. Atoms are indivisible and indestructible particles. D.O.B - 1766
Provided the first hint that an atom is made of even smaller particles. D.O.B - 1856.
He was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons. D.O.B - 1871
Electrons move in definite orbits around the nucleus, much like planets circle the sun. These orbits, or energy levels, are located at certain distances from the nucleus. D.O.B -
He discovered the presence of the neutron. D.O.B - 1891
According to the theory of wave mechanics, electrons do not move about an atom in a definite path, like the planets around the sun.