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400 BC
'grandfather' of the Atomic Theory because he recognized that atoms exsisted and were mechanically bound -
Said that there were 4 elements, earth, water, fire, and air. Believed in reasoning instead of scientific experiments and said democritisus' atom theory wasn't right.
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established the Law of Conservation of Mass
suggested that element cannot be broken down into simpler components and combined elements would create chemical compounds. -
father of modern atomic theory • 5 parts to theory • includes elements are composed of atoms • also includes elements atoms are identical in mass
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Atomic theory proposed by John Dalton
Dalton's theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights. -
Beginning in 1895 physicist J. J. Thomson theorized that cathode rays produced in Crookes' tubes must be composed of what he called "corpuscles", a single type of negatively charged particle.
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discovered electron
• described nature of cathode rays
• plum pudding model of atom- Joseph John Thomson proposed that the atom was a sphere of positive electricity (which was diffuse) with negative particles imbedded throughout after discovering the electron, a discovery for which he was awarded the Nobel Prize in physics in 1906. -
measured charge of an electron • oil drop experiment • completed with Thomson
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atoms can emit quanta • Einstein used Plancks work to study photons
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Ernest Rutherford's experiment that showed that atoms are mostly emppty space except for the nucleus
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model of the atom
electrons travel in specified energy levels
• spectrum lines produced when electrons move
• introduced that electrons orbit around the nucleus in an atom -
gold foil experiment • atom has small positive nucleus, remainder is empty space • predicted existence of neutrons
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• electrons have properties of both waves and particles • group of waves named after him
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demonstrated that
mass and energy are conserved in the
atomic process -
showed mathematically that waves can be used to describe electrons in atoms • determined probability location of electrons in atoms
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• uncertainty principle
• impossible to determine the position
and the momentum of a particle at the same time
• cloud model aka quantum mechanical mode -
helped with the development of the nuclear model and discovered neutron
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•Succeeded in making man-made elements. •won the 1951 Nobel Prize in Chemistry for "discoveries in the chemistry of the transuranium elements", contributed to the discovery and isolation of ten elements