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460
Democritus
Democritus Atom Democritus was a greek philospher who lived from 460 to 370 B.C. He was the first person to call particles "atoms". He claimed that everything was made up of atoms, and they were infinite in number, always moving, unique, and could combine with other atoms. -
John Dalton
Dalton's Atomic Theory Dalton John was an English meteorologist who switched to chemistry. He lived from 1766 to 1844. In 1803 he proposed the "Atomic Theory" This identified chemical elements as a specific type of atom. His model explained that atoms looked like spheres, with each of the elements having its own size. -
J.J Thomson
Thomson's Atomic Model J.J Thomson was a British physicist. He was born in 1857 and died in 1940. He found that there was a positive and negative charge in atoms, and called the negative ones electrons. In 1904 he created an atomic model called the "plum pudding model" -
Ernest Rutherford
Rutherford's Theory Ernest Rutherford (1871-1937) was a British physicist. After his gold foil experiment, he came to the conclusion that most of the mass of an atom was contained in its nucleus, and that is where the positive charge of the atom is located. -
Niels Bohr
Bohr's Theory Niels Bohr (1885-1962) combined Rutherford's description of the nucleus and Planck's theory about quanta and explained what happens inside of the atom and created a picutre of atomic stucture. He was the first to discover that electrons travel in seperate orbits around the nucleus. -
James Chadwick
Chadwick's Atomic Theory James Chadwick (1891-1974) proved the existence of nuetrons, that Rutherford had predicted. He also said that the atomic number is determined by the number of protons in an atom.
