The History of the Atomic Theory

By coolic

  • Isaac Newton

    Proposed a mechanical universe with small solid masses in motion.

  • John Dalton

    Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass.

  • Michael Faraday

    Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism

  • Julius Plucker

    Built one of the first gas discharge tubes ("cathode ray tube").

  • Dmitri Mendeleev

    Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law.

  • George Johnstone Stoney

    Proposed that electricity was made of discrete negative particles he called "electrons".

  • Joseph John Thomson

    Used a CRT to experimentally determine the charge to mass ratio of an electron =1.759 x 108 coulombs/gram.

  • Ernest Rutherford

    Studied radiations emitted from uranium and thorium and named them alpha and beta. He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.

  • Frederick Soddy

    Observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements, discovered "half-life", made initial calculations on energy released during decay.

  • Henry Moseley

    Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass.

  • Francis William Aston

    Discovered the existence of isotopes through the use of a mass spectrograph.

  • Niels Bohr

    Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons.

  • Louis Victor De Broglie

    Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality.

  • James Chadwick

    Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron.

  • Enrico Fermi

    Conducted the first controlled chain reaction releasing energy from the atoms nucleus.