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Science Periodic Table
11 months ago
Leucippus and Democritus 450BC The first proponents of an atomic theory were the Greek philosophers Leucippus and Democritus who proposed the following model in the fifth century B.C. 1. Matter is composed of atoms separated by empty space through which the atoms move.
Aristotle 300BC When the Atomic Theory was discovered, Aristotle did not believe in it. He believed that all substances were made of Fire, Water, Air, and Earth. He taught his beliefs, and he was so well known for his teachings, most believed him to be right.
John Dalton 1803 Chemist John Dalton was born September 6, 1766, in Eaglesfield, England. During his early career, he identified the hereditary nature of red-green color blindness. In 1803 he revealed the concept of Dalton's Law of Partial Pressures.
Joseph Thomson 1897 In 1897, J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas.
Ernest Rutherford 1911 Rutherford at Manchester, 1907–1919. Ernest Rutherford discovered the nucleus of the atom in 1911.
Niels Bohr 1913 Bohr Atomic Model : In 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus.
James Chadwick 1932 Chadwick discovered the neutron 1932. seem to be the only particle in the nucleus. atom). For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2.
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