Development of Atomic Theory

By chernandez3
  • 442

    BC, Greek Era - Democritus

    Theorized that all matter is made of atoms which became known as the atomic theory. Came up with the idea that atoms are in a void.

  • Isaac Newton

    Proposed a mechanical universe with small solid masses in motion. Law of mechanics which shows that everything moves around no matter how small. Contributed to our understnading of atoms- This has told us that atoms are made out of small moving particles.

  • John Dalton

    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. Also proposed that these atoms are spherical, and are in motion.

  • X-rays developed

    Wilhelm Rontgen discovered that certain chemicals glowed when exposed to cathode rays. These rays weren't deflected by a magnetic field produced in the cathode ray tube. He named these X-rays. While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays.

  • Radiation, Energy, and the Atom

    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.

  • Electrons Discovered

    JJ Thomson discovers the electron, using properties of cathode rays.

  • Early Quantum Theory Developed

    Max Planck introduced what would be known as quantum theory, stating that electromagnetic energy could only be emitted in quantized form. His quanta are now called photons by physicists.

  • Einstein and The Nature of Light

    Albert Einstein, creates special and general theories of relativity, and hypothesizes about the particle nature of light. This was the basis of nuclear energy.

  • Charge of an Electron is Measured (1908-1917)

    Robert Millikan measured the charge of a single electron. This is known as the elementary charge, one of the fundamental physical constants

  • Structure of an Atom Developed (1909-1911)

    Ernest Rutherford known as the father of nuclear physics, developed the theory for the structure of the atom. He used a gold foil experiment, observing the scattering of alpha particles, and demonstrated for the first time the existence of the atomic nucleus.

  • Bohr Improves the Atomic Model

    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 also integrated the Planck quantum theory, stating that when electrons change orbits they emit a quantum of discrete energy.

  • Math Describes Electron Charges

    Erwin 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.

  • The Neutron is Discovered

    James Chadwick discovers the neutron component of the atomic nucleus, explaining the nuclear fission of uranium 235. This also made it possible to produce elements heavier than uranium in the lab.

  • Nuclear Fission Developed

    Otto Hahn, regarded as the father of nuclear chemistry, discovers nuclear fission, along with Lise Meitner.