History of Atomic Theory

  • 700 BCE

    Acharya Kanad

    Acharya Kanad
    Some consider him as the actual father of "Atomic Theory". Named them anu and thought of how they might interact with each other, as we know today as atoms. How everything was made up of smaller indivisible objects that had similar properties to each type but could build different things together.
  • 400 BCE

    The Beginning: Democritus

    The Beginning: Democritus
    Democritus devised and atomic theory and presented the idea that everything was made up of smaller indivisible objects.
    His theory states:
    - Everything is composed of “atoms”, which are physically, but not geometrically, indivisible
    - Between atoms, there lies empty space
    - Atoms are indestructible
    - Atoms have always been, and always will be, in motion
    - There are an infinite number of atoms, and kinds of atoms, which differ in shape, and size.
  • Period: 380 BCE to

    Aristotle: Stagnation

    Aristotle halted the advancement of scientific discovery related to the atomic theory. He believed everything was made up of earth, air, fire, and water. He also had the backing of the catholic church, anyone who didn't believe his model was shunned or killed. For almost 2000 years he held of the scientific advancement of atomic theory
  • 800


    Famous for the claims of turning lead into gold. Alchemy was the belief that everything is spiritually connected even medals, and that medals weren't stuck to one spot on the periodic table but rather different forms of the same thing. Hence lead being an immature younger form of gold. Spanning from the time of Aristotle to the scientific revolution
  • John Dalton

    John Dalton
    The thinking of Democritus returns as John Dalton's Atomic theory:
    - Everything is composed of atoms, which are the indivisible building blocks of matter and cannot be destroyed.
    - All atoms of an element are identical.
    - The atoms of different elements vary in size and mass.
    - Compounds are produced through different whole-number combinations of atoms.
    - A chemical reaction results in the rearrangement of atoms in the reactant and product compounds.
  • JJ Thomson

    JJ Thomson
    Thomson discovered the electron and proved Dalton wrong in that atoms where made up of smaller parts. He discovered them with an experiment using a cathode ray tube. He developed the plum pudding model. Negatively charged particles within a positively charged area.
  • Marie Curie

    Marie Curie
    Marie discovered radioactivity, along with the radioactive elements Polonium and Radium. Along with developing X-rays.
  • Hantaro Nagaoka

    Hantaro Nagaoka
    Famous for developing the Saturnian model of the atom. In which electrons orbit a mass of positively charged material like the rings of Saturn.
  • Ernest Rutherford

    Ernest Rutherford
    Rutherford furthered the developments of Thompson's model and discovered the nucleus. He proposed the idea that the negatively charged atoms orbited around the positive nucleus.
  • Albert Einstein

    Albert Einstein
    E=MC^2, famous for his theory of general relativity.
  • Max Planck

    Max Planck
    Best Known for his development of the quantum theory of energy. Planck's constant is used to describe the actions of waves and particles at the atomic level. His findings used by Rutherford to build his atomic model.
  • Lois de Broglie

    Lois de Broglie
    in his 1924 PhD he accurately predicted the wave nature of electrons.
  • Satyendra Nath Bose

    Satyendra Nath Bose
    He derived Planck's quantum radiation law without using classic physics, which he did by counting the states of identical properties.
  • Werner Heisenberg

    Werner Heisenberg
    Famous for his uncertainty principle. Heisenberg stated that the position and momentum of a electron cannot be know at the same time. And stated electrons do not travel in neat orbits.
  • Wolfgang Pauli

    Wolfgang Pauli
    Pauli's Principle States that no two electrons in an atom can have the same sets of quantum numbers.
  • Erwin Schrödinger

    Erwin Schrödinger
    Schrödinger is famous for developing the cloud model of the atom, staying that electrons go about an atoms more so in a messy cloud than in neat orbits. he could also mathematically determine where these electrons would most likely be.
  • James Chadwick

    James Chadwick
    In 1932 he discovered the neutron in the nucleus of an atom after bombarding beryllium atoms with alpha particles, and how they affect the atomic weight of an atom.
  • Niels Bohr

    Niels Bohr
    Niels Bohr created the basis of quantum theory. How electrons an be viewed as a particle or a wave but not at the same time. He also developed the new model of the atom with Rutherford
  • Lise Meitner

    Lise Meitner
    Discovered that nuclear fission can produce enormous amounts of energy.
  • Dorothy Hodgkin

    Dorothy Hodgkin
    Developed protein crystallography and advanced the X-Ray version of it to help determine the 3D Structures of Molecules.
  • Richard F. W. Bader

    Richard F. W. Bader
    States that electron density in molecules matters along with that there are no atomic orbitals.
  • Rudolph Arthur Marcus

    Rudolph Arthur Marcus
    Studied how swapping element's electrons could drive chemical reactions.
  • Robert J. LeRoy

    Robert J. LeRoy
    Famous for formulating the "LeRoy Radius" which defines the inter-nuclear distance between two atoms a at which the LeRoy-Bernstein theory becomes valid.