1. History of the Atom Notes zDalton pg 88-89 Zumdahl zThomson pg 91 Figure 4.3 Zumdahl pg 97 & 98 LeMay zMillikan pg 98 LeMay zRutherford pg 100-101 LeMay Figure 3-16 pg 91 –93 Zumdahl zMoseley pg 104 LeMay zChadwick pg 94 Zumdahl zBohr pg 287-288 Zumdahl Figure 10-17 pg 284 –287 Zumdahl

2. History of the Atom White Board Presentations Democritus (example) zGreek philosopher, around 400 BCE zProblem with previous model: no system or explanation, just “magic” zModel: z“atomos” compose the world- tiny, indivisible particles that retain the chemical identity of the element

4. History of the Atom White Board Presentations John Dalton zEnglish schoolteacher, 1766-1844 zProblem w/ previous model: No logical/scientific structure or rules zAtomic Theory Of Matter: y5 postulates (next slide) zModel:

5. Atomic Theory of Matter 1.Each element is composed of atoms 2.All atoms of a given element are identical 3.All atoms of different elements are different (#2 and #3 often combined) 4.Atoms are neither created nor destroyed 5.Atoms combine to form compounds and a given compound has the same relative numbers and kinds of atoms

7. History of the Atom White Board Presentations JJ Thomson zEnglish physicist, 1856-1940 zProblem w/ previous model: no subatomic particles zExperimental Evidence: cathode ray tube experiment where particles smaller than atoms are shown to have negative charge (electrons) with a small mass to charge ratio zModel: Plum Pudding Model:

9. History of the Atom White Board Presentations Robert Millikan zAmerican physicist, 1869-1953 zProblem w/ previous model: no known amount of charge of an electron zExperimental evidence: oil drop experiment where (-) charged oil drops pass between (+) plates and rate of fall is measured. All were multiples of 1.60 x 10 -19 C (one e - ). zHe also calculated the mass of an e - based on the charge and the known mass:charge ratio. zModel: (looks the same as Thomson’s)

11. History of the Atom White Board Presentations Ernest Rutherford zScientist from New Zealand, 1871-1937 zProblem w/ previous model: does not account for  particles bouncing back zExperimental evidence: gold foil experiment where he shot (+) charged  particles at very thin gold foil and saw evidence for a very small, dense, positively charged core to the atom. zModel: Nuclear atom

13. History of the Atom White Board Presentations Henry Moseley zEnglish scientist, 1887-1915 (Rutherford’s student) zProblem w/ previous model: does not account for elemental differences zExperimental evidence: X-Ray diffraction patterns of metals showed that each element has a unique positive charge in the nucleus that determines the atoms identity (atomic number) zModel: (looks the same as Rutherford’s)

15. History of the Atom White Board Presentations Sir James Chadwick zEnglish physicist, 1891-1974 zProblem w/ previous model: mass of protons did not account for mass of nucleus and a nucleus of all protons (+) would repel and fall apart zExperimental evidence: He bombarded metals (beryllium) with  particles, causing a radiation that was both neutral and a mass similar to a proton zModel: (looks the same as Rutherford's, but with neutrons in the nucleus as well)

17. History of the Atom White Board Presentations Niels Bohr zDanish physicist, 1885-1962 zProblem w/ previous model: did not account for specific energy levels of e - seen in the light spectrum analysis zExperimental evidence: The energy spectrum of hydrogen shows discrete “quanta” of energy involved in e - configurations zModel: (Bohr model)

19. Info on Experimentation: zThomson's Experiment: http://www.aip.org/history/electron/jj1897.htm http://www.aip.org/history/electron/jj1897.htm zCathode Ray tube- http://www.youtube.com/watch?v=O9Goyscbazk http://www.youtube.com/watch?v=O9Goyscbazk zMillikan's Experiment: http://webphysics.davidson.edu/applets/pqp_preview/content s/pqp_errata/cd_errata_fixes/section4_5.html http://webphysics.davidson.edu/applets/pqp_preview/content s/pqp_errata/cd_errata_fixes/section4_5.html zOil Drop- http://www.youtube.com/watch?v=XMfYHag7Liwhttp://www.youtube.com/watch?v=XMfYHag7Liw zHere’s what the drops would actually look like… don’t watch the whole thing. It’s hypnotic- http://www.youtube.com/watch?v=SxcxN_UVuFI http://www.youtube.com/watch?v=SxcxN_UVuFI zRuthorford's Experiment: http://www.rsc.org/chemsoc/timeline/pages/1911.html http://www.rsc.org/chemsoc/timeline/pages/1911.html zGold Foil- http://www.youtube.com/watch?v=XBqHkraf8iEhttp://www.youtube.com/watch?v=XBqHkraf8iE