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Aristotle's Theory
-Aristotle was responsible for this theory
-The model for this theory was adopted around 460 B.C.
-This model was adopted because Aristotle was very influencial during his time, and what he believed was all matter was made of; Earth, Wind, Fire, and Water, so everyone followed his theory
-His theory was chosen over Democritus' "indivisible" theory.
-This theory was not proven because it was wrong, and 2000 years later people moved away from this theory.
-Aristotle tutored Alexander the Great -
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Democritus
-Democritus was responsible for this theory
-This theory was adopted around the same time as Aristotle's theory, around 460 B.C.
-Democritus believed that atoms were indivisible, that people could "cut" substances until no longer possible. This was the very first theory of matter.
-His idea was debated with Aristotle's idea, Democritus lost the debate even though Aristotole was wrong.
-Democritus lived from 490 B.C.- 370 B.C. -
John Dalton
-John Dalton created this theory
-Theory was adopted around 1790
-His theory held 5 postulates
-All elements are made of "atoms"
-All atoms of an element are identical
-All atoms of different elements are different
-Atoms can combine to form compunds
-Atoms cannot be created/destroyed, only changed
-John Dalton was known as the "Father od the Atomic Theory"
- Dalton lived from 1766-1844 -
J.J. Thomson
-J.J. Thomson was responsible for this theory
-The model for Thomson's theory was adopted in 1890
-Thomson had 2 experiments, one where he discovered the elctron and one where he showed how electrons were distibuted.
-Cathode Ray Tube experiment showed how atoms had negative "pieces" in them called electons
-Also found the mass to charge ratio of an electron
-Plum Pudding model showed where the electrons and other charges are spread out through the atom
-Thomson lived from 1856-1940 -
Henri Becquerel
-Henri Becquerel created this theory
-This theory was adopted in 1896
-Henri did work with flourescent materiels, uranium, and potassium. Basically, he wrapped the materiels in photo paper and put them in the sun. By doing so, the initial result of this experiment was that uranium produced radiation without an external source of energy
-Becquerel lived from 1852-1908 -
Marie and Pierre Curie
-Marie and Pierre Curie created this theory
-This theory was adopted in 1898
-Theory was adopted when Pierre and Marie were doing work with radioactive substances
-While working with these substances, they discovered radium and polonium.
-Marie Curie lived from 1867-1934
-Pierre Curie lived from 1859-1906 -
Quantum Model
-Created by researchers in the 1900s
-The Quantum Model was created based upon other scientist's theories ansd mathematics of their experiments
-In short words, the Quantum Theory gives the location of an electron exactly.
-The Quantum Model is the atomic model that we use today -
Robert Millikan
-John Millikan was responsible for this theory
-The experiment for this thory was conducted in 1909
-Millikan put a charge on a drop of oil and thenmeasured how strong of an electric field was required to keep the oil from falling, then calculated the force of gravity per drop.
-This experiment revelaed the charge of an electron.
-Robert Millikan lived from 1868-1953 -
Earnest Rutherford
-Earnest Rutherford was responsible for this theory
-The experiment for this theory was conducted in 1910
-Rutherford set up an experiment where he fired radioactive energy at a thin layer of gold foil. Expecting it to go straight through, he was suprised when the rays bounced in every direction. This experiment proved that most of the atom was made of empty space while in the middle there was a substance, which he called a "nucleus"
-Rutherford lived from 1871-1937 -
Niels Bohr
-Niels Bohr was responsible for this theory
-This experiment was conducted in 1922.
-Bohr's model is a planetary model, in which different negatively charged electrons orbit around the nucleus of an atom
-Bohr's model was an enhanced version of Ruhterford's model, so some poeple called it the "Rutherford-Bohr Model"
-Bohr's model is not correct
-Niels Bohr lived from 1855-1962 -
James Chadwick
-James Chadwick created this theory.
-Theory was adopted around 1932
-Discovered this theory by repeating an experiment that European scientists made, looking for a neutral particle with the same mass of a protonand zero charge.
-His theory was proven when he found the proton.
-Chadwick recieved the Nobel Prize for his discovery
-Chadwick lived from 1891-1974
