Atomic Theory

  • 500 BCE

    Leucippus of Miletus and his student Democritus of Abdera come up with the "atom"

    Leucippus of Miletus and his student Democritus of Abdera come up with the "atom"
    The idea that matter is made up of tiny, indivisible particles or atoms came from these two greek philosophers. The Greek word "atomos" means indivisible.
  • 480 BCE

    Empedocles devised the theory that all substances are made of four pure, indestructible elements.

    Empedocles devised the theory that all substances are made of four pure, indestructible elements.
    Fire, Water, Earth, Air. Empodocles tried to simplify our complex world into basic elements. He also believed all matter was consious. He also believed matter was held together by a fundamental force of the universe he described as "Love" and pushed apart by another force called "Strife".
  • Alchemist develop a Theory that all metals are composed of Mercury and Sulfur, and that all matter is composed of elements shown in the picture.

    Alchemist develop a Theory that all metals are composed of Mercury and Sulfur, and that all matter is composed of elements shown in the picture.
    They beginning to try and change base metals into gold.
  • John Dalton formulated the first modern description of an atom.

    John Dalton formulated the first modern description of an atom.
    He described atoms as indivisible and indestructible. Different elements had atoms of differing size and mass. Suggested that chemical reactions were the results of the rearrangement of atoms
  • Marie Curie experiments on uranium rays and discovered that they remained constant, no matter the condition or form of the uranium.

    Marie Curie experiments on uranium rays and discovered that they remained constant, no matter the condition or form of the uranium.
    She theorized, the rays came from the element's atomic structure, these rays are now known as radioactivity. This discovery kickstarted modern-day atomic physics.
  • J.J. Thomson discovered the electron with a cathode ray tube. Created the Plum Pudding Model.

    J.J. Thomson discovered the electron with a cathode ray tube. Created the Plum Pudding Model.
    Thomson realized that the accepted model of an atom did not account for negatively or positively charged particles. Electrons were the raisins and the positive charge was the dough. This explained the electrical properties due to electrons
  • Planck proposed that energy is radiated in packets call "quanta".

    Planck proposed that energy is radiated in packets call "quanta".
    He was able to determine that the energy of each quantum is equal to the frequency of the radiation multiplied by a universal constant that he derived. This constant is now one of the basic constants of physics
  • Hantaro Nagaoka developed the "Saturnian" system for the atom.

    Hantaro Nagaoka developed the "Saturnian" system for the atom.
    This model stated that the atom is inherently unstable by radiating continuously, the electron would gradually lose energy and spiral into the nucleus. No electron could thus remain in any particular orbit indefinitely. This means that atoms will eventually lose their chemical properties.
  • Einstein extended Planck's hypothesis to explain the photoelectric effect.

    Einstein extended Planck's hypothesis to explain the photoelectric effect.
    Which is the emission of electrons by a metallic surface when irradiated by light or photons. This helped determine the particle-wave duality of electrons.
  • Ernest Rutherford discovered that the plum pudding structure is incorrect.

    Ernest Rutherford discovered that the plum pudding structure is incorrect.
    By firing alpha particles at gold foil, and detecting the ricocheting particles, they determined that the atom consisted of a small, dense, positively charged nucleus, with negatively charged electrons surrounding it.
  • Bohr discovered that electrons travel in separate orbits around the nucleus.

    Bohr discovered that electrons travel in separate orbits around the nucleus.
    He also determined that the number of electrons on the outermost orbit determines the properties of the element. Additionally, his theoretical work contributed to the understanding of nuclear fission.
  • James Chadwick discovers the Neutrons.

    James Chadwick discovers the Neutrons.
    After Rutherford discovered the atomic nucleus and the proton, the discrepancy in atomic masses led to the discovery of a neutral particle through the use of a Neuton Chamber.
  • de Broglie developed his theory of electron waves.

    de Broglie developed his theory of electron waves.
    The notion of matter on the atomic scale might have the properties of a wave were rooted on Einstein's theory that light might be observed as a wave under certain conditions, and as a particle under other conditions. De Broglie’s idea of an electron with the properties of a wave offered an explanation of the restricted motion.
  • Satyendra Nath Bose discovered bosons/

    Satyendra Nath Bose discovered bosons/
    Working together with Albert Einstein, he defined one of the two basic classes of subatomic particles. Unfortunately, much of the credit for discovering the boson, or "God particle," was given to British physicist Peter Higgs
  • Wolfgang Pauli created the Pauli exclusion principle.

    Wolfgang Pauli created the Pauli exclusion principle.
    This principle states that in an atom no two electrons can occupy the same quantum state simultaneously.
  • Erwin Schrödinger developed the "Electron Cloud Model"

    Erwin Schrödinger developed the "Electron Cloud Model"
    Schrödinger mathematically determined regions in which elections would most likely be found. These regions are known as Orbitals.
  • Heisenberg proposed his uncertainty principle.

    Heisenberg proposed his uncertainty principle.
    He stated that an electron's velocity and position can not be known simultaneously as to measure either with radiation would alter the other
  • Lise Meitner discovered that when uranium was bombarded with neutrons, it would undergo fission.,

    Lise Meitner discovered that when uranium was bombarded with neutrons, it would undergo fission.,
    News of the splitting of the atom and its awesome possibilities was brought by Bohr to scientists in the United States and ultimately resulted in the Manhattan Project.
  • Robert J. LeRoy created the LeRoy radius, a technique for mathematically defining the radius of a small molecule, which is key to understanding the forces within and outside the molecule.

    Robert J. LeRoy created the LeRoy radius, a technique for mathematically defining the radius of a small molecule, which is key to understanding the forces within and outside the molecule.
    He also developed predictive computer modeling, using computers to simulate chemical reactions
  • Richard F. W. Bader discovered that electron density is very important in explaining the behavior of atoms in the molecules.

    Richard F. W. Bader  discovered that electron density is very important in explaining the behavior of atoms in the molecules.
    He argues that electron density is more accurate as molecules have no orbits, but electron density remains consistent. Although this goes against conventional theories, there are several pieces of evidence that support this theory.
  • Justin Yien discovers the ability to imprint human consciousness onto subatomic particles.

    Justin Yien discovers the ability to imprint human consciousness onto subatomic particles.
    Combining this with quantum computers, humans now live within a simulated reality,