Atom vector

Atomic Theory Timeline

  • 460

    Democritus of Adbera

    Democritus of Adbera
    Democritus was the first philosopher to propose the idea of an indivisible particle. He called this particle an “atomos”.
  • Isaac Newton

    Isaac Newton
    Newton proposed a universe in which small solid masses are in motion.
  • Antoine Lavoisier

    Antoine Lavoisier
    Antoine proposed the Law of Conservation of Mass, stating that matter cannot be created or destroyed. This represented the beginning of modern chemistry.
  • Benjamin Franklin

    Benjamin Franklin
    Franklin conducted his experiment with a key attached to a string hoping the key would conduct electricity. Proving the conductivity also had proven the idea that matter had positive and negative charges, allowing it to flow.
  • Joseph Proust

    Joseph Proust
    Proust would help support the idea compounds always have the same elements in the same proportions. His theory is known as the Law of Conservation of Composition.
  • John Dalton

    John Dalton
    John dalton made his mark by proposing a new atomic theory. It stated- 1. all matter is made of small particles to be called atoms; 2. atoms of a given element have unique properties that no other elements share; 3. atoms cannot be split, created, or destroyed; 4. Atoms of various elements combine to make whole number ratio compounds; 5. Atoms combine, rearrange, or separate in chemical reactions.
  • Michael Faraday

    Michael Faraday
    Michael Faraday discovered the electromagnetic induction. This discovery was when attempting to induce a current by a circuit, it is essential to change the magnetic field.
  • Julius Plucker

    Julius Plucker
    Plucker successfully constructed one of the first cathode ray tubes which would lead to many new discoveries.
  • Dmitri Mendeleev

    Dmitri Mendeleev
    Dmitri Mendeleev's greatest accomplishment was ordering the periodic table form the lightest atomic mass to the heaviest atomic mass. Therefore the chemical properties also formed a trend.
  • James Clerk Maxwell

    James Clerk Maxwell
    Maxwell proposed that the void around an atom was actually an electromagnetic field.
  • William Crookes

    William Crookes
    His major achievement was discovering that the cathode rays were actually negatively charged, by studying the ways the ray moved due to the magnetic field.
  • G.J. Stoney

    G.J. Stoney
    Stoney proposed that electricity was made up of negative particles called electrons.
  • Henry Becquerel

    Henry Becquerel
    Henry discovered some chemicals spontaneously decompose and give off high penetrating rays.
  • Joseph John Thomson

    Joseph John Thomson
    The previous hypotheses stated that the fundamental building block was the size of the simplest atom, hydrogen. J.J. Tomson disagreed and instead said it was over 1000 times smaller, this lead to his discovery of the electron.
  • Marie & Pierre Curie

    Marie & Pierre Curie
    Their main accomplishment was the discovery of the two elements radium and polonium. These two elements are important to life because radium is an isotope heat source.
  • Frederick Soddy

    Frederick Soddy
    Soddy studied spontaneous decomposition of radioactives elements into all kinds of isotopes or entirely new elements. He also discovered "half life".
  • Max Planck

    Max Planck
    Planck discovered the constant at which the energy and frequency come out in. This constant is also known as Planck's constant and is 6.63 x 10 ^ -34 J * s.
  • Hantaro Nagaoka

    Hantaro Nagaoka
    Nagaoka created a Saturnian model of the atom in which flat rings of electrons revolved around a positively charged particle.
  • Richard Abegg

    Richard Abegg
    Abegg discovered that inert gases contained stable electron configurations. This explained their chemical inactivity.
  • Albert Einstein

    Albert Einstein
    Albert Einstein came up with the photoelectric effect. This states that when quanta of light energy strikes an atom in the metal, it will force the metal to emit electrons.
  • Hans Geiger

    Hans Geiger
    Hans developed a machine that was able to click when contacted with alpha particles. This came in handy for future atomic experiments.
  • Robert Millikan

    Robert Millikan
    Robert Millikan is known for his oil drop experiment. With this experiment he uncovered the size and the charge of an electron.
  • Ernest Rutherford

    Ernest Rutherford
    Ernest Rutherford discovered that these electrons were part of a bigger picture. Rutherford discovered the nucleus.
  • H.G.J. Moseley

    H.G.J. Moseley
    Moseley determined nuclei charges on most atoms and worked to reorder the periodic table by atomic number as opposed to atomic mass.
  • Niels Bohr

    Niels Bohr
    After studying a hydrogen atom, Bohr proposed an atomic model known as the planetary model.
  • Francis William Aston

    Francis William Aston
    Aston was able to discover isotopes by way of a mass spectrograph.
  • Louis deBroglie

    Louis deBroglie
    He proposed that electrons could behave like waves under certain conditions. This led scientists to understand that atoms did not behave like solar systems.
  • Erwin Schrödinger's

    Erwin Schrödinger's
    Erwin Schrödinger's main discovery was the wave equation. His interpritation of the physical meaning of wave function criticzied that of the Copenhagen theory.
  • Werner Heisenberg

    Werner Heisenberg
    Heisenberg proposed Principle of Indeterminacy which states that we cannot know both the position and velocity of a particle. Instead he used the frequencies of spectral lines in order to derive a formula describing the atom.
  • James Chadwick

    James Chadwick
    Chadwick is most famously known for discovering neutrons in an atom.
  • Otto Hahn, Lise Meitner

    Otto Hahn, Lise Meitner
    These two were able to verify that heavy elements capture neutrons and make unstable products that then undergo fission. As the fission continues, more neutrons can be ejected.
  • Enrico Fermi

    Enrico Fermi
    Fermi was the first scientist to conduct a controlled chain reaction that releases energy from the atom's nucleus.
  • Aristotle

    Aristotle theorized that everything around us was made up of 4 basic elements; earth, fire, water, and air. He also believed that matter could be divided endlessly. Surprisingly, this ideaology was believed for over 2000 years!