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Democritus
Democritus was a greek philospher/scientist. He was influenced by his mentor, Leucippus, who orginally thought of the atomic theory. Democritus philosophized that matter cannot be destroyed and is able to be divided into smaller particles. He belived that atoms can differ in size, shape and temperature, are always movingm and are also invisible. -
John Dalton
John Dalton was an english chemist/teacher. He had a fascination with meteorology, but is most famously known for his Atomic Theory. He theorizied that all elements are composed of atoms which are indivisble and indestructible. Also, while atoms of a particular element were identical, different elements had atoms of contrasting size and mass. -
Dmitri Mendeleev
Dmitri Mendeleev arranged elements into seven different groups with similar properties. He found out that the properties of those elements "were periodic functions of their atomic weights". This lead to the discovery of the Periodic Law. -
William Crookes
Sir William Crookes was an english chemist who invented a device called the Crookes tube or Cathode Ray Tube. The device was a sealed galss tube with nearly almost all the air removed. Using two electrodes and a high voltage one is able to see the glass wall glow because the electrons hit the object in the glass tube and casts a shaow. This indicts that rays travel in straight lines. -
Nagaoka
In disagreement with Thomson's model, Nagaoka established another model of the atom that showed a postively charged center is surrounded by multiple revolving electrons. -
J.J. Thompson
J.J. Thompson modified Crookes experiment by adding two plates outside the galss tube, one negatively charged the other positive. He discovered when particles are heated they give off particles which are smaller than atoms. These particles are attracted to a postively charged object. Also, atoms contain small negatively charged particles called electrons. -
Millikan
Robert Andrews Millikan conducted the famous Oil-Drop experiment which was way more successful at determining the cahrge of an electron than previous testings. Millikan proved that the mass of an electron is extremly small and confirmed electrons carrie a negative charge. -
Ernst Rutherford
Ernst Rutherford's Gold Foil Experiment consisted of firing a beam of alpha particles through a sheet of gold foil. In order for the experiment's hypothesis to be correct each particle would have to go directly through the foil, this was mostly correct. However, there were a small amount of particles would land slightly away form the path. Sometimes, a single particle would get fired right back to the person conducting the experiment. -
Niels Bohr
Niels Bohr discovery was that electrons travel around the nucleus like planents orbit around the son. -
Erwin Schrodinger
Erwin Schrodinger was an Austrian physicist who developed the atom model Bohr created a bit further. He used mathematical equations to pinpoint the chance of finding an electron in a specific spot. The atomic model developed by Schrodinger is known as the quantum mechanical model of the atom. This model does not specify the exact path of an electron, but predicts the odds of the location the the electron.
