History of the Atomic Structure

  • Mechanical Universe; Isacc Newton

    Proposed a mechanical universe with small solid masses in motion.
  • Proposed Atomic Theory; John Dalton

    Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass.
  • Electrolysis; 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.
  • Cathode Ray Tube; J. Plucker

    J. Plucker built one of the first gas discharge tubes (""cathode ray tube""). "
  • Periodic Law; Dmitri Mendeleeff

    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.
  • Electric and Magnetic Field; James Clerk Maxwell

    Proposed electric and magnetic fields filled the void.
  • Electrons Proposed; G.J. Stoney

    Proposed that electricity was made of discrete negative particles he called "electrons".
  • Cathode discoveries; Sir William Crookes

    Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. 
  • Canal Rays Study; E. Goldstein

    Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron. 
  • Xrays; Wilhelm Roentgen

    Using a CRT he observed that nearby chemicals glowed. Further experiments found very penetrating rays coming from the CRT that were not deflected by a magnetic field. He named them "X-rays". 
  • X-Ray Studies; Henri Becquerel

    While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays. 
  • Idea of Quanta; Max Planck

    Used the idea of quanta (discrete units of energy) to explain hot glowing matter.
  • Saturanian Model of an Atom; Nagaoka

    Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle.
  • Stable Electron Gases; Abegg

    Discovered that inert gases had a stable electron configuration which lead to there chemical inactivity.
  • Isotopes Discovered; Aston

    Discovered the existence of isotopes through the use of a mass spectrograph. 
  • Anti-Particles Proposed; Paul Dirac

    Proposed anti-particles. Anderson discovered the anti-electron (positron) in 1932 and Segre/Chamberlain detected the anti-proton in 1955.
  • First Controlled Chain Reaction; Enrico Fermi

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