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470
(B.C) Democritus, Greece.
"by convention bitter, by convention sweet, but in reality atoms and void" source:http://scienceworld.wolfram.com/biography/Democritus.html -
Newton, England
Projected a mechanical universe with small solid masses in motion. source: http://atomictimeline.net/index.php -
Dalton, England
Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. source: http://www.timelineindex.com/content/view/1228 -
G.J Stoney, Ireland
Claimed atoms could eject small negatively charged particles, which he named as electrons. Also proposed electricity was made of electrons. source: http://www.buzzle.com/articles/timeline-of-atomic-structure.html -
JJ Thomson, England
Experimented on a Cathode Ray Tube to determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram. source: http://www.timelineindex.com/content/select/1375/912,2,70,1375 -
Planck, Germany
Used the idea of quanta (discrete units of energy) to explain hot glowing matter. source: http://atomictimeline.net/index.php -
Period: to
timeline of Atomic Theory
Events placed on the timeline are recognised due to the scentists who had discovered or experimented on ideas which are used today. their work is credited upon for their experiemnts and ideas of atomic theory.
* please note that the dates and months( not the year) of these events are wrong and should be ignored for their own good.
** also, the first one is supposed to be 470 B.C. NOT 470 A.C.
*** Have fun.=] -
Nagoaka, Japan
Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle. source: http://www.cartage.org.lb/en/themes/sciences/physics/atomicphysics/atomicstructure/atomictimeline/atomictimeline.htm -
Millikan, America
Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron. source: http://atomictimeline.net/index.php -
E Rutherford, New Zealand
Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. source: http://www.buzzle.com/articles/timeline-of-atomic-structure.html -
H.G.J. Mosely, England
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. source: http://www.cartage.org.lb/en/themes/sciences/physics/atomicphysics/atomicstructure/atomictimeline/atomictimeline.htm -
Bohr, Denmark
Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of successive orbital shells of electrons source: http://atomictimeline.net/index.php -
James Chadwick, England
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. source: http://www.cartage.org.lb/en/themes/sciences/physics/atomicphysics/atomicstructure/atomictimeline/atomictimeline.htm