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Series01AtomsAndBohrModel

Series01AtomsAndBohrModel - Atoms Bohr Model and the...

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Atoms and the Bohr Model Reading: Gray: (1-1) to (1-7) OGC: (1.3), (1.4), (3.2), (4.1) to (4.3) I-1
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Outline of First Lecture I. General information about the atom II. How the theory of the atomic structure evolved A. Charge and Mass of the atomic particles 1. Faraday 2. Thomson 3. Millikan B. Rutherford ʼ s Model of the atom I-2
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H Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra Sc Y La Ac Ti Zr Hf V Nb Ta Cr Mo W Mn Tc Re Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg B Al Ga In Tl N P As Sb Bi O S Se Te Po F Cl Br I At He Ne Ar Kr Xe Rn Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 6 Atoms consist of: Protons Neutrons Electrons Mass (a.m.u.) ~1 ~1 1/1836 Charge (eu) +1 0 -1 Si Ge Sn Pb C C 12.01 6 I-3
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10 -5 Å 1 Å = 10 –10 m 1 Å (Nucleus) Electron Cloud Nucleus not drawn to scale! Note: I-4
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Atomic Size? Charge and Mass of an Electron? Charge and Mass of a Proton? Mass Distribution in an Atom? HOW DO WE KNOW: I-5
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A Timeline of the Atom 400 BC 0 1800 -450 Empedocles- earth, air, fire, water -400 Democritus: idea of an atom; is water like sand: smooth from afar, coarse up close? atoms had no mass, just filled space 1661 Robert Boyle: disputes 4 element theory; postulates an element is a substance that can not be reduced into simpler substances 1808 John Dalton postulates that atoms have weight and combine to form substances 1811 Amadeo Avogadro: postulates that compounds are formed from molecules 1820 Faraday: charge/mass ratio of protons 1885 E. Goldstein: discovers a positively charged sub-atomic particle 1898 J. J. Thompson finds a negatively charged particle called an electron. 1909 Robert Millikan experiments to find the charge and mass of the electron. 1911 Ernest Rutherford discovers the nucleus of an atom. 1913 Niels Bohr introduces his atomic theory. 1919 The positively charged particle identified by Goldstein is found to be a proton. 1920s Heisenburg, de Broglie, and Schrodinger. 1932 James Chadwick finds the neutron. 1964 The Up, Down, and Strange quark are discovered. 1974 The Charm quark is discovered. 1977 The Bottom quark is discovered. 1995 The Top (and final) quark is discovered. 1850 1900 1950 ....... ...... I-6
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1.0 cm 1.0 cm 1.0 cm 19.28 g N A = 6.022 x 10 23 atoms / mole Atomic weight of gold = 197.0 g / mole How many moles of gold? 19.28 g 197.0 g / mole = 0.09786 moles How many gold atoms? (0.09786 moles)x(6.022 x 10 23 atoms / mole)=5.893 x10 22 atoms There are approx. 5.9 x10 22 atoms in 1 cm 3 of gold Calculating the Number of Atoms in One Cubic Centimeter of Gold I-7
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Calculating Atomic Size Assuming each atom takes up a volume of π r 3 , we can calculate the radius of a single atom: 1.0 cm 3 of gold, containing 5.9 x 10 22 atoms 1.0 cm 3 (5.9 x 10 22 ) volume of one atom number of atoms total volume radius of one gold atom = 1.6 x 10 -8 cm, or 1.6 angstoms r = π r 3 4 3 4 3 I-8
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The Person Behind The Science Michael Faraday 1791-1867 Began experimenting on electricity in 1813 under Sir Humphrey Davy Moments in a Life Highlights Bookbinder turned self-taught scientist Discovered magnetic optical rotation Invented the Dynamo , a device capable of converting electricity into motion (1821) Discovered electromagnetic induction (1831) Published a three volume treatise titled Experimental Researches in Electricity (1839-1855) I-9
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