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400 BCE
Democritus
all material bodies are made up of indivisibly small atoms. -
384 BCE
Aristotle
the deductive validity of any argument can be determined by its structure rather than its content -
350 BCE
plato
there are only five solid shapes whose sides are made from regular polygons -
The alcemeist
The major finding is invented experimental techniques (distillation, for example) and laboratory tools -
Lavoisier
Lavoisier major finding is determined that oxygen was a key substance in combustion -
John Dalton
John Dalton. His major finding is oxygen combined with either one or two volumes of nitric oxide in closed vessels over water. -
newlands law of octaves
when the elements are arranged in ascending order of atomic mass, every eighth element has comparable properties -
Mendeleevs table
Periodic table. Major finding when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern -
photoelectric effect
electrical spark passing between two spheres would occur more readily -
Discovery of the radioactivity
the atom was neither indivisible nor immutable. -
Discovery of the electron
all atoms contain tiny negatively charged subatomic particles or electrons -
plum pudding model
Thomson's plum pudding model of the atom had negatively-charged electrons embedded within a positively-charged -
Rutherford gold foil experiment
a tiny, dense nucleus was causing the deflections. -
Robert Milikan
Major finding is accurate determination of the charge carried by an electron -
mosleys atomic number
The major finding is the atomic number is the number of positive charges in the atomic nucleus -
Bohr planetary model
Electrons orbit the nucleus in orbits that have a set size and energy -
Discovery of the proton
a nuclear reaction which led to the first 'splitting' of the atom -
Charge of electron
Electron charge, Millikan Oil Drop Experiment -
Schrodinger Equation
The fundamental equation of the science of submicroscopic phenomena known as quantum mechanics -
Heisenberg uncertainty principle
we cannot know both the position and speed of a particle, such as a photon or electron, with perfect accuracy -
Discovery of the neutron
central to the extraordinary developments in atomic physics in the first half of the 20th century -
Plancks Quantum theory
Different atoms and molecules can emit or absorb energy in discrete quantities only -
Albert Einstein
Albert Einstein. His major finding is the photoelectric effect.