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John Dalton
Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass. -
Bohr Model
The Bohr Model has an atom consisting of a small, positively-charged nucleus orbited by negatively-charged electrons. Here's a closer look at the Bohr Model, which is sometimes called the Rutherford-Bohr Model. http://chemistry.about.com/od/atomicstructure/a/bohr-model.htm -
William Crooke
bibliographyDiscovered 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. http://atomictimeline.net/index.php
https://www.google.hn/search?q=william+crooke&source=lnms&tbm=isch&sa=X&ei=cyIlUpKXBsvJ -
J.J. Thomson
Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram.
Studied "canal rays" and found they were associated with the proton H + http://atomictimeline.net/index.php
https://www.google.hn/search?q=william+crooke&source=lnms&tbm=isch&sa=X&ei=cyIlUpKXBsvJsAS0hIDADw&ved=0CAcQ_AUoAQ&biw=1024&bih=491#q=j+j+thomson&tbm=isch&facrc=_&imgdii=_&imgrc=en3M5N2I02u5eM%3A%3BVf_RFAPyMAG2GM%3Bhttp%253A%252F%252Fupload.wikimedia.org%252Fwikipedia%252Fco -
Quanum Mechanical Model
The quantum mechanical model shows that electrons don’t have set orbital but are in random motion confined within the areas of electron probability distribution. The quantum mechanical model works for all elements whereas the Bohr model works only for hydrogen.
http://atomicstructureforelectrons.webs.com/quantummechanicalmodel.htm -
Ernest Rutherford
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. http://atomictimeline.net/index.php
https://www.google.hn/search?q=william+crooke&source=lnms&tbm=isch&sa=X&ei=cyIlUpKXBsvJsAS0hIDADw&ved=0CAcQ_AUoAQ&biw=1024&bih=491#q=ernest+rutherford&tbm=isch&facrc=_&imgdii=_&imgrc=Xuhwff2FcBKiAM%3A%3BL2U7 -
Rutherford Model
Rutherford reasoned that if Thomson's model was correct then the mass of the atom was spread out throughout the atom. Then, if he shot high velocity alpha particles (helium nuclei) at an atom then there would be very little to deflect the alpha particles. He decided to test this with a thin film of gold atoms. As expected, most alpha particles went right through the gold foil but to his amazement a few alpha particles rebounded almost directly backwards.
http://www.iun.edu/~cpanhd/C101webnotes/m -
J.J. Thomson's Model
With the plum pudding model in mind, Rutherford expected very minimal alpha particle deflections as they were bombarded on the foil. Hence, the scintillations were only supposed to be observed right behind the foil, exactly opposite to the source of alpha particles. Alas, although majority of the flashes were indeed observed behind the foil, a few were also seen near the source. Rutherford guessed that they should be concentrated in a very small volume in the center.
http://www.universetoday.co -
Dalton's Model
He discovered that certain gases only could be combined in certain proportions even if two different compounds shared the same common element or group of elements. Through deductive reasoning and experimentation, he made an interesting discovery. His findings led him to hypothesize that elements combine at the atomic level in fixed ratios. This ratio would naturally differ in compounds due to the unique atomic weights of the elements being combined.
http://www.universetoday.com/38169/john-dalton -
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. http://atomictimeline.net/index.php
https://www.google.hn/search?q=william+crooke&source=lnms&tbm=isch&sa=X&ei=cyIlUpKXBsvJsAS0hIDADw&ved=0CAcQ_AUoAQ&biw=1024&bih=491#q=niels+bohr&tbm=isch&facrc=_&imgdii=_&imgrc=1EUB35OzrPfr3M%3A%3BDWG8f96JtgHYlM%3Bhttp%253A%252F%252Frememberingrescue.files.wordpress.com%252F2 -
James Chadwick
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. http://atomictimeline.net/index.php
https://www.google.hn/search?q=william+crooke&source=lnms&tbm=isch&sa=X&ei=cyIlUpKXBsvJsAS0hIDADw&ved=0CAcQ_AUoAQ&biw=1024&bih=491#q=james+chadwick&tbm=isch&facrc=_&imgdii=_&imgrc=YE82OQa-AAZRzM%3A%3BF8ZfgEjpO886YM%3Bhttp%253A%252F%252Fwww.wired.com%252Fimages%252Farticle%252Ffull%252F2009%252F02%252FJames_Chadwick.jpg%3Bhttp%253A%252F%
