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400
Democritus
~400 B.C.
Atomos-indivisible
First to identify possibility of an atom -
401
Aristotle
300s BC
Four "elements": earth, fire, air, water
believed in reasoing instead of scientific experiments
dismissed Democritus' atom idea as "worthless" -
John Dalton
1803, 1805, 1808
father of modern atomic theory
5 parts to a theory
includes elements are composed of atoms
also includes elemnt's atoms are identical in mass -
Joseph John Thomson
discovered electron
described nature of cathode rays
plum pudding model of atom -
Robert Millikan
measured charge of an electron
oil drop experiment
completed with Thomson -
Max Planck
atoms can emit "quanta"
Einstein used this scientist's work to study photons -
Alchemists
Known as some of the first experimentalists
searched for the philosopher's stone
strove to accomplish transmutation of base metals into silver or gold -
Ernest Rutherford
gold foil experiment
atom has small positive nucleus, remainder is empty space
predicted existence of neutrons -
Niels Bohr
planetary model of atom
electrons travel in specified energy levels
spectrum lines produced when electrons move -
Louis de Broglie
electrons have properties of both waves and particles
group of waves named after this scientest -
Erwin Schrodinger
showed mathematically that waves can be used to describe electrons in atoms
determined probability location of electrons in atoms -
Werner Heisenberg
"uncertainty principle"
impossible to determine the position and the momentum of a particle at the same time
"cloud" model aka quantum mechanical model -
James Chadwick
helped with the development of the nuclear model
discovered neutron
