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Democritus suggests the atom
In the 4th century BC Democritus suggested that the entire universe was made up of teeny tiny units. He called them atoms from the Greek word atomos which means "indivisible". -
John Dalton Continued
4: Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
5: In chemical reactions, atoms are combined, separated, or rearranged. -
John Dalton makes his discoveries
The color blind, English chemist John Dalton does experiments that lead him to develop the Law of Definite Proportions. There were five main points in this law.
1:Elements are made of extremely small particles called atoms.
2:Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3:Atoms cannot be subdivided, created, or destroyed. -
J.J. Thomson Contributes his Portion
In 1897 J.J. Thompson performed his Cathode Ray Tube experiment. In this experiment Thomson constructed a Crookes tube with an electrometer on one side, out of the direct path of the cathode rays. Thomson could trace the path of the ray by observing the phosphorescent patch it created where it hit the surface of the tube. Thomson observed that the electrometer only registered a charge when he deflected the cathode ray to it with a magnet. Through this he created the Plum Pudding Model -
Thomson's Crooks tube
Thomson's illustration of the Crookes tube by which he observed the deflection of cathode rays by an electric field (and later measured their mass to charge ratio). Cathode rays were emitted from the cathode C, passed through slits A (the anode) and B (grounded), then through the electric field generated between plates D and E, finally impacting the surface at the far end. -
Ernest Ruherford's Gold Foil Experiment
