Atomic Theory history

  • 460

    Democritus BC
    Greece idea:the atomic theory, which asserted that the universe is composed of two elements: the atoms and the void in which they exist and move.
    contribution:He stated the first atomic theory. His hypothesis on atoms is remarkably similar to modern science's understanding of atomic structure. He also gave the idea that The shape and existence of all things are determined by void and atoms through the differences in shape, position and arrangement of the atoms and the proportion of
  • Period: 460 to


  • Isaac Newtown
    idea: Proposed a mechanical universe with small solid masses in motion. contribution:He argued that light were composed of corpuscles, or particles, which much later led to the quantum properties of matter. He was one of the earliest thinkers in modern science to suggest an “atomic” nature of matter, even though early Greeks did also suggest that.
  • John Dalton
    Theory: all matter consists of tiny particles, atoms are indestructible and unchangeable and when elements react, their atoms combine in simple, whole-number ratios contribution:He was the first to prepare a table of atomic weights. He rationalised the various laws of chemical combination which were in existence at that time. He also stated that chemical reactions occur when atoms are rearranged and all atoms of the same element are identical.
  • G J Stoney

    []( Ireland
    theory:Stated that electricity was made up of describe negative particles called electrons contribution:Was the first to suggest that electrons were a building block of the atom. She assisted in the discovery of the electron by j.j. Thomson.
  • J J Thomson Britan
    idea: First person to theorize the atom contains positive and negative particles, and demonstrated the latter which he called electrons. contribution:He proved that the hydrogen atom contained only 1 single electron. He created the basis of the beginning of atomic structure description.
  • Max Planck
    idea:This theory stated that radiant energy can only be emitted or absorbed in discrete quantities, like small packages. contribution:He gave the name quantum to the smallest quantity of energy than can be emitted in the form of electromagnetic radiation.
  • Hantaro Nagaoka
    idea:Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle. contribution:First to present a saturian atomic model close to the presently accepted model. The model described atoms as electropositive balls that had electrons scattered in them, like the rasins in rasin bread.
  • Robert Andrews Millikan
    idea:Determind the unit charge of the electron whith his oil drop experiment at the university of Chicago thus allowing for the calculation of the mass of the electron and the positively charged atom contribution:Discovered the weight of an electron is 1836 times smaller
  • E. Rutherford Zealand/british idea:Proposed the nuclear atom as a result of the gold-foil experiment. contribution:Proposed that all of the positive charge and all of the mass of the atom occupied a small volume at the center of the atom and that most of the volume of the atom was empty space occupied by the electrons.he also proposed the existence of the third atomic particle, the neutron.
  • H.G.J. Moseley
    idea:Discovered that the energy of x-rays emitted by the elements increased in a linear fashion with each successive element int he periodic table. contribution:He proposed that the relationship was a function of the positive charge on the nucleus. This rearranged the periodic table by using the atomic number instead of atomic mass to represent the progression of the elements. This new table left additional holes for elements that would soon be discovered.
  • Neils Bohr idea:Proposed that the outer orbit of an atom could hold more electrons than the inner orbit. contribution:
    Bohr’s atomic model introduced some quantum mechanics aspects to the atomic model, and, more importantly , it provided a theoretical frame for Ruberg’s formula, which had been observed only empirically.
  • James Chadwick
    idea:Used alpha particles to discover a neutral atom particle with a mass close to a proton. contribution:Discovered the electron. He was a collaborator of Rutherford’s. The discovery of the neutron lead directly to the discovery of fission and ultimately to the atomic bomb