Welcome to 3.091 Lecture 3 September 14, 2009 Atomic Models: Rutherford & Bohr
1 Periodic Table Quiz 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 Name Grade /10 Image by MIT OpenCourseWare.
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La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Loony chemistry professor needs partner: seeking educated graduate to develop hazardous experiments testing young lab assistants. cannot be referring to 3.091! must be the other chemistry professor source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
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The Structure of the Atom status report ca. end of the 19th century * atom is electrically neutral * -ve charge carried by electrons * e - has very small mass bulk of the atom is +ve, most mass resides in +ve charge Question: what is the spatial distribution of charge inside an atom?
Figure 1.18 Image by MIT OpenCourseWare.
Figure 1.19 γ rays β particles α particles 10-cm lead 0.5- cm lead Paper Image by MIT OpenCourseWare.
Rutherford-Geiger-Marsden experiment Image by MIT OpenCourseWare.
Image by MIT OpenCourseWare.
Image by MIT OpenCourseWare.
Marsden's Analysis Trajectory of incident α particle θ b gold nucleus Scattering of an α-particle which approaches a heavy nucleus with an impact parameter b. Image by MIT OpenCourseWare.
principles of modern chemistry: * recognize patterns * develop a quantitative model that - explains our observations - makes predictions that can be tested by experiment
Bohr Postulates for the Hydrogen Atom 1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e - 3. Newtonian mechanics applicable to orbiting e - 4. E electron = E kinetic + E potential 5. e - energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3, 6. Planck-Einstein relation applies to e - transitions: ΔE = E f - E i = hν = hc/λ c = νλ
Bohr Postulates for the Hydrogen Atom 1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e - 3. Newtonian mechanics applicable to orbiting e - 4. E electron = E kinetic + E potential 5. e - energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3, 6. Planck-Einstein relation applies to e - transitions: ΔE = E f - E i = hν = hc/λ c = νλ
Image by MIT OpenCourseWare.
Bohr Postulates for the Hydrogen Atom 1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e - 3. Newtonian mechanics applicable to orbiting e - 4. E electron = E kinetic + E potential 5. e - energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3, 6. Planck-Einstein relation applies to e - transitions: ΔE = E f - E i = hν = hc/λ c = νλ
Bohr Postulates for the Hydrogen Atom 1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e - 3. Newtonian mechanics applicable to orbiting e - 4. E electron = E kinetic + E potential 5. e - energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3, 6. Planck-Einstein relation applies to e - transitions: ΔE = E f - E i = hν = hc/λ c = νλ
UV Visible Infrared 6000 K Planck suggests that light is composed of energy packets or quanta. The elementary unit of e-m radiation is the photon. Radiation intensity 5000 K Classical prediction 6000 K E = hν 4000 K 3000 K 0 500 1000 1500 2000 2500 3000 Wavelength (nm) Image by MIT OpenCourseWare.
Bohr Postulates for the Hydrogen Atom 1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e - 3. Newtonian mechanics applicable to orbiting e - 4. E electron = E kinetic + E potential 5. e - energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3, 6. Planck-Einstein relation applies to e - transitions: ΔE = E f - E i = hν = hc/λ c = νλ
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source unknown. All rights reserved. This image is excluded from our Creative Commons license.for more information, see http://ocw.mit.edu/fairuse.
source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
Isotopes of Hydrogen hydrogen 1766 Henry Cavendish, London deuterium 1931 Harold Urey, Columbia U. tritium 1934 Ernest Rutherford, Cambridge U.
1803 1904 1911 Dalton proposes the indivisible unit of an element is the atom. Thomson discovers electrons, believed to reside within a sphere of uniform positive charge (the "plum pudding" model). Rutherford demonstrates the existence of a positively charged nucleus that contains nearly all the mass of an atom. 1913 1926 Bohr proposes fixed circular orbits around the nucleus for electrons. In the current model of the atom, electrons occupy regions of space (orbitals) around the nucleus determined by their energies. Image by MIT OpenCourseWare.
J. J. Thomson (1856-1940) Cathode ray = Charged particle = Electron (1897) charge-to-mass ratio of electron (1897) Henri Becquerel (1852-1908) Uranium emits rays that fog photographic film (1869) Robert Millikan (1868-1953) Charge and mass of electron (1909) J.J Thomson "Plum pudding" model of atom (1904) Marie and Pierre Curie (1867-1934, 1854-1906) Radioactive elements polonium and radium (1898) Ernest Rutherford (1871-1937) α and β particles (1898) Ernest Rutherford Nuclear model of atom (1911) Ernest Rutherford Proton (1920) James Chadwick (1891-1974) Neutron (1932) Image by MIT OpenCourseWare.
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