Atomic Theory Timeline

By 28SRiveros
  • 430 BCE

    Democritus

    Democritus
    Believed that atoms were uniform, solid, hard, incompressible, and indestructible, and that they moved in infinite number through empty space until stopped.
  • 427 BCE

    Plato

    Plato
    Theorized that the soldi forms of matter are composed of indivisible elements shaped like triangles.
  • 330 BCE

    Solar System Model

    Solar System Model
    Proposed by Plato. It placed the planets in the solar system in order from the Earth.
  • 700

    The Alchemists

    The Alchemists
    Believed that all metals were formed from mercury and sulfur.

  • Robert Boyle

    Robert Boyle
    Created Boyle's law that stated that a gas's pressure and volume are inversely proportional.

  • Amadeo Avogrado

    Amadeo Avogrado
    Made two hypotheses stating 1) that equal volumes of gas contains equal numbers of molecules and 2) that elementary gases such as hydrogen, nitrogen, and oxygen were composed of two atoms.

  • Antone Lavoisier

    Antone Lavoisier
    Made the law of conservation of mass that stated that in a chemical reaction, mass is neither created nor destroyed.

  • John Dalton

    John Dalton
    Suggested that all matter was compromised of indivisible and indestructible atoms with distinct masses and properties.

  • Billiard Ball Model

    Billiard Ball Model
    Created by John Dalton. This model defined an atom to be a ball-like structure.

  • Dmitri Mendeleev

    Dmitri Mendeleev
    Created the periodic table by arranging the atoms in order of increasing atomic mass.

  • JJ Thompson

    JJ Thompson
    Discovered the electron and then went on to propose a model for the structure of the atom.

  • Pierre and Marie Curie

    Pierre and Marie Curie
    Discovered the strongly radioactive elements polonium and radium.

  • Plum Pudding Model

    Plum Pudding Model
    Created by JJ Thompson. Showed the electrons embedded in a uniform sphere of positive charge like blueberries stuck to a muffin.

  • Albert Einstein

    Albert Einstein
    Mathematically predicted the size of both atoms and molecules.

  • Robert Millikan

    Robert Millikan
    Precisely determined the magnitude of the electron's charge.

  • Ernest Rutherford

    Ernest Rutherford
    Described the atom as having a tiny dense, and positively charged core called the nucleus.

  • Neils Bohr

    Neils Bohr
    Proposed a model of the atom where the electron was only able to do certain orbits around the atom's nucleus.

  • Henry G.J. Mosely

    Henry G.J. Mosely
    Arranged the elements in the periodic table according to atomic numbers.

  • Werner Heisenberg

    Werner Heisenberg
    Formulated a type of quantum mechanics based on matrices.

  • Erwin Schrodinger

    Erwin Schrodinger
    Formulated a wave equation that accurately calculated the energy levels of electrons in atoms.

  • Electron Cloud Model

    Electron Cloud Model
    Made by physicist Erwin Schrodinger. Represents the area around an atom's nucleus where electrons are most likely to be found.

  • James Chadwich

    James Chadwich
    Discovered the neutron.