|Event Date:||Event Title:||Event Description:|
|Sir Isaac Newton's Experiments and Theories||Newton described universal gravitation and the three laws of motion which dominated the scientific view of the physical universe for the next three centuries. Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws by demonstrating the consistency between Kepler's laws of planetary motion and his theory of gravitation, thus removing the last doubts about heliocentrism and advancing the scientific revolution|
|Experiments of John Dalton||Dalton’s idea was that each chemical element is composed of a unique type of atom, and that the atoms differed by their masses. He devised a system of chemical symbols and, having ascertained the relative weights of atoms, arranged them into a table. In addition, he formulated the theory that a chemical combination of different elements occurs in simple numerical ratios by weight, which led to the development of the laws of definite and multiple proportions.|
|Discovery of the Electron||J. J. Thomson dramatically changed the modern view of the atom with his discovery of the electron. Thomson's work suggested that the atom was not an "indivisible" particle as John Dalton had suggested but, a jigsaw puzzle made of smaller pieces.|
|The origination of the Quantum Theory||The quantum theory revolutionized our understanding of atomic and subatomic|
|Development of a model of an atom by Nagoaka||Nagaoka developed an early, incorrect "planetary model" of the atom. The model was based around an analogy to the explanation of the stability of the Saturn rings (the rings are stable because the planet they orbit is very, very massive). The model made two predictions: a very massive nucleus (in analogy to a very massive planet) ; electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces).|
|Measuring the charge of an electron-Robert A. Millikan||Millikan measured the charge on an electron with his oil-drop apparatus.|
|Discovery of alpha and beta radiation and the nucleus of the atom||Ernest Rutherford discovered alpha and beta radiation along with the nucleus of an atom. His theories revolutionized the scientific views of the time.|
|Experiments of H.G.J Moseley||The physicist H.G.J. Moseley conducted a series of experiments where he bombarded targets made out of different kinds of metals with cathode rays.
He found that the heavier the atomic mass of the element, the shorter was the wavelength and the more penetrating were the X-rays.
|Refining the theory on electrons||Neils Henrick Bohr further refined the nuclear model by proposing that electrons moved only in restricted, successive orbital shells and that the outer, higher-energy orbits determined the chemical properties of the different elements. Furthermore, Bohr was able to explain the spectral lines of the different elements by suggesting that as electrons jumped from higher to lower orbits, they emitted energy in the form of light.|
|Discovery of the Neutron||James Chadwick discovered a third type of subatomic particle, which he named the neutron.|