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460
Democritus
He was the Ffrst person to suggest that matter could not be infinitely divided. He made up the term “atomos” (later became “atom”) to describe the tiny particles that make up matter and that move through empty space. Atoms can not be created, destroyed, or further divided” -
Period: 501 to 505
Scientists
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John Dalton
He marked the beggining of the development of the modern atomic theory. Revived the term "atom". He siad items are the smallest particles of matter and are individual and indestructible. -
SIr William Crookes
Sir William Crookes noticed a green flash of light within a cathode ray tube while working in a dark laboratory.
He later discovered that the radiation went completely through the tube and not only on the Zn-S coating. -
J.J. Thompson
He designed a series of CRT experiments at Cambridge to determine the ratio of the particle’s charge to its mass.
He Concluded that the mass of the particle was much less than that of the Hydrogen atom, which disproved Dalton’s theory that atoms were indivisible. -
Robert Milikan
He designed an oil drop apparatus to determine the charge of the electron. He discovered the mass of the electron. He also determined the magnitude of the charge of the electron. -
Ernest Rutherford
He studied how positivly charged a-particles interacted with solid matter. -
James Chadwick
He demonstrated that the nucleus had another neutral subatomic particle, the nuetron. -
Aristotle
He completely denied the existence of atoms due to personal ideas about nature. His ideas about matter took over those of Democritus- back to square one.