The history of the atom
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THE HISTORY OF THE ATOM. Greek Philosophers (400 B.C.). Aristotle- believed the everything was made of the 4 elements (air, fire, water, and land). Each substance contained a varying portion of each element.

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THE HISTORY OF THE ATOM

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THE HISTORY OF THE ATOM


Greek Philosophers (400 B.C.)

  • Aristotle- believed the everything was made of the 4 elements (air, fire, water, and land). Each substance contained a varying portion of each element.

  • Democritus-believed everything was made of invisible and indivisible particles called “atomus” = ATOMS


Ben Franklin -1748

Determined there were positive and negative charges in nature.


Antoine Lavoisier-1790

Law of conservation of matter- matter isneither created nor destroyed in anyprocess (you did anexperiment with the test tube and the flask)


Joseph Louis Proust - 1799

Law of constant composition - any sample of agiven compound always contains the samepercent of each element by mass.


John Dalton-1803

Created the Atomic Theory of Matter

Contains 4 postulate:

  • Each element is made of invisible and indivisible particles called atoms. (Democritus) wrong

  • All atoms of an element are identical. wrong

  • Atoms can not be created or destroyed in a reaction.

    (Laviosier)

    4. A given compound always has the same relative numbers and kinds of atoms. (Proust)


Michael Faraday - 1839

  • Suggested there was a connection between the structure of the atom and electricity.


E. Goldstein - 1886

Isolated the proton.


J.J. Thomson - 1896

Isolated the electron. (cathode tube in the journal)


Henri Becquerel - 1896

Accidentally discovered that uranium gave off invisible rays. Photo plates were developed when put close to the sample of uranium. (journals)


Marie and Pierre Curie - 1898

  • Named Becquerel’s invisible rays “radiation”.

  • Isolated the radioactive elements polonium and radium.


Ernest Rutherford - 1909

  • Isolated alpha and beta radiation.

  • Found all of the atom’s protons were in the center of the atom and called this the nucleus. (gold foil experiment in journal)


Robert Millikan - 1909

Found the mass (grams) and the charge (columbs) of the electron. (Famous oil drop experiment done at he University of Chicago.)


Niels Bohr - 1911

Proved electrons were in energy levels around the nucleus. (The current model changes part of Bohr’s idea.)


James Chadwick - 1932

Found the nucleus of the atom also contained neutral particles; he called them neutrons.


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