He also integrated the Planck quantum theory, stating that when electrons change orbits they emit a quantum of discrete energy.Įrwin Shrodinger described how electrons move in wave form, and developed the Schrodinger equation which describes how the quantum state of a system changes with time. Neils Bohr developed the Bohr atomic model, with electrons travelling in orbits around the nucleus, and chemical properties being determined by how many electrons are in the outer orbits. He used a gold foil experiment, observing the scattering of alpha particles, and demonstrated for the first time the existence of the atomic nucleus. Structure of an atom developed (1909-1911)Įrnest Rutherford known as the father of nuclear physics, developed the theory for the structure of the atom.
This is known as the elementary charge, one of the fundamental physical constants. Robert Millikan measured the charge of a single electron. This was the basis of nuclear energy.Ĭharge of an electron measured (1908-1917) His quanta are now called photons by physicists.Īlbert Einstein, creates special and general theories of relativity, and hypothesizes about the particle nature of light. Max Planck introduced what would be known as quantum theory, stating that electromagnetic energy could only be emitted in quantized form. JJ Thomson discovers the electron, using properties of cathode rays. Pierre and Marie Curie theorized that radioactive particles cause atoms to break down, then releasing radiation that takes the form of energy and subatomic particles. These rays weren't deflected by a magnetic field produced in the cathode ray tube. Wilhelm Rontgen discovered that certain chemicals glowed when exposed to cathode rays.
Sir William Crookes constructed a primitive cathode ray tube, which later became the basis for television. Also proposed that these atoms are spherical, and are in motion. John Dalton, a British chemist and physicist, developed a theory that matter is simply composed of atoms of different weights and is combined in ratios by weight. Democritus, a Greek philosopher, co-originated the thought (with his teacher, Leucippus) that all matter is composed of indivisible elements.