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500
Democritus
DEMOCRITUS: (460-370 B.C.)
Democritus was the first person to suggest that matter could not be infinitely divided. He created the term "atomos", which later became "atom" in modern terms. Though, he could never figure out what held atoms together. He could be considered the Father of Atomic Theory, considering he was the first person to study atoms. "Atoms can not be created, destroyed, or further divided."
-Democritus -
Aug 25, 600
Aristotle
ARISTOTLE (385-322 B.C.)
Aristotle disagreed with Democritus' theory on atoms and how he thought that they moved through empty space. In fact, he completely denied the existence of atoms. His ideas eventually took over those of Democritus, and more people believed Aristotle. This man's ideas caused Atomic Theory to be set back 'to square one'. -
John Dalton
JOHN DALTON (1766-1844)
John Dalton's studies marked the official beginning of the development of modern atomic theory. He took Democritus' theories and revised them based off of his own personal research- also reviving the term "atomos" into "atom". Unlike Democritus' ideas, Dalton's were widely accepted. He believed that atoms are the smallest particles of matter, and are indivisible and indestructible. -
John Dalton (Cont.)
"Atoms can be rearranged, separated, or combined to form new things, but cannot be created, destroyed, or divided in the process."
-John Dalton -
J.J Thompson
J.J Thompson (1856-1940)
He preformed CRT experiments to determine the ration particles charged to its mass. He discovered the mass of Cathode Ray particles are lighter than the mass Hydrogen atoms. J.J Thompson proposed the "Plum Pudding Model" of the atom. -
Robert Millikan
ROBERT MILLIKAN (1868-1953)
He designed an oil drop apparatus to determine the charge of an electron. He determined that the magnitude of the charge of the electron was 1.602x10(-19) coulombs. (The electron carries a charge of -1) He discovered the mass of the electron using the known charge/mass ratio. -
Ernest Rutherford (2)
Ernest Rutherford refined his ideas of the nucleus to include positively charged particles called protons. -
Ernest Rutherford
ERNEST RUTHERFORD (1871-1937)
He studied how positively charged -particles interacted with solid matter. He came to the conclusion, after the gold foil experiment, that Thomson's atom model was incorrect. Rutherford calculated that an atom was mostly just made up of empty space for electrons to move around in. He claimed that the main source of the atom's mass and positive charge was the nucleus. -
James Chadwick
JAMES CHADWICK (1891- 1974)
He demonstrated that the nucleus had another subatomic particle, the neutron. Chadwick won the 1935 Nobel prize for his discovery. -
Sir William Crookes
SIR WILIAM CROOKES
He discovered, while observing a cathode ray tube, radiation went completely through the tube and not only on the Zn-S coating. He calls these rays "cathode rays". This discovery later helped the invention of the television.
