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THE HISTORY OF THE ATOM

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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  1. THE HISTORY OF THE ATOM

  2. 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

  3. Ben Franklin -1748 Determined there were positive and negative charges in nature.

  4. 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)

  5. Joseph Louis Proust - 1799 Law of constant composition - any sample of agiven compound always contains the samepercent of each element by mass.

  6. 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)

  7. Michael Faraday - 1839 • Suggested there was a connection between the structure of the atom and electricity.

  8. E. Goldstein - 1886 Isolated the proton.

  9. J.J. Thomson - 1896 Isolated the electron. (cathode tube in the journal)

  10. Henri Becquerel - 1896 Accidentally discovered that uranium gave off invisible rays. Photo plates were developed when put close to the sample of uranium. (journals)

  11. Marie and Pierre Curie - 1898 • Named Becquerel’s invisible rays “radiation”. • Isolated the radioactive elements polonium and radium.

  12. 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)

  13. Robert Millikan - 1909 Found the mass (grams) and the charge (columbs) of the electron. (Famous oil drop experiment done at he University of Chicago.)

  14. Niels Bohr - 1911 Proved electrons were in energy levels around the nucleus. (The current model changes part of Bohr’s idea.)

  15. James Chadwick - 1932 Found the nucleus of the atom also contained neutral particles; he called them neutrons.

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