TIMELINE of Atomic Theory

Timeline created by JesseLiu
In History
  • -500 BCE


    Alchemists expanded the Empedocles theory. They tried to obtain the real element base on the 4 element fire, wind, water, and earth, which laid the foundation of the period table
  • -442 BCE


    Democritus first proposed the theory of atomic-- " consists of invisible particles called atoms and a void (empty space). " He believes that if you cut a matter until it can not be divided, the smallest piece call atoms, which is divisible in physically.
  • John Dalton

    John Dalton
    Dalton's law concluded that all matter is made up of particles called atoms, meanwhile, all atoms of the same element are identical in mass and size, but they are different in mass and size when they are not the same atoms of the same element.
  • Marie Sklodowska Curie

    Marie Sklodowska Curie
    Marie Sklodowska Curie finds the radioactive elements polonium and radium. Curie creates the word "radioactivity" to describe why the uranium remained constant, whatever the condition or form of the uranium. She conjectures that the ray comes from the element's atomic structure, which makes a huge contribution to the development of atomic theory.
  • Thomson

    Thomson discovered the electrons by equipment cathode ray, tube. He first proposes that an atom should contain a positive charge and a negative charge
  • Hantaro Nagaoka

    Hantaro Nagaoka
    Hantaro Nagaoka argues against J.J Thompson states" the atom was a positive charged sphere with electrons scattered throughout it." He believes that positive center (Nucleus) was surrounded by rings of electrons. He names his model as “The Saturnian Model”
    as it looks like Saturnian.
  • Bohr

    Bohr's well-known contribution to atomic theory is the Bohr model. He first finds that electrons spin in different orbits around the nucleus, meanwhile, it shows that an atom is a tiny and positive charge nucleus around the orbiting electrons.
  • Rutherford

    Rutherford believed that there is something error in Thomson's model. Thus, he designs the famous gold foil experiment by using alpha practices and reverse Thomson's model, which demonstrates there is a tiny nucleus in an atom.
  • Einstein

    The best-known hypothesis of Albert Einstein is relativity, which is E = mc^2. It demonstrates the relationship between energy and matter. He is also well-known as the chemistry area of quantum mechanics. He proposes the law of the photoelectric effect, which become the foundation of the quantitative laws of photochemistry
  • Henry Moseley

    Henry Moseley
    Henry organized elements by atomic number instead of atomic mass, which makes the atomic table more precise.
  • Planck

    Max Planck propose that quantum theory of energy. His discovery speed up the understanding of atomic and subatomic processes.
  • deBroglie

    Louis deBroglie propose deBroglie hypothesis which all matters have properties of wave and particles based on de Broglie wavelength.
  • Satyendra Nath Bose

    Satyendra Nath Bose
    Bose was named for him. He made a very great contribution of Bose statistics. His research now is proof that is marked the profound importance in the classifications of fundamental particles and the development of nuclear physics.
  • Pauli

    Wolfgang Pauli is famous for the exclusion principle and the theory of non-relativistic spin. He stated that there is not an atom that contains two electrons that can own the same four quantum numbers.
  • Schrödinger

    Schrödinger expand the Bohr model further. He describes the probability of finding an electron in a certain position in math. Unlike the Bohr model, it predicts the likelihood of the position of the electrons. If the cloud is most dense, the chance of finding the electron is greatest.
  • Heisenberg

    Werner Heisenberg proposed uncertainty principle, which you can't get the location of a particle and its momentum(velocity) at the same time
  • Chadwick

    Chadwick's well-known research is neutron. He shot the alpha particles at beryllium atoms, which cause unknown radiation. It made of particles with a neutral electrical charge and the approximate mass of a proton. It is known as the neutron.
  • Irene Joliot Curie

    Irene Joliot Curie
    Irene Joliot Curie discovers how to create man-made Radioactivity
  • Robert J. LeRoy

    Robert J. LeRoy
    Robert J. LeRoy has two main achievements in the chemistry area; One is the development of the Leroy-Bernstein theory and the second one is coming up with Le Roy radius which is significant to the spectroscopy of molecules
  • Richard F.W. Bader

    Richard F.W. Bader
    Richard F.W. Bader discovers that the electron density is vital in explaining the conduct of atoms in molecules, which demonstrate atomic orbitals do not exist in the molecules.
  • Period:
    -492 BCE
    -432 BCE


    Empedocles states that all matters are comprised of 4 elements, which are fire, air, water, and earth.