CHE_106_Lecture4_2009

CHE_106_Lecture4_2009 - Chemistry 106 Lecture 4 Topics...

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Chemistry 106 Lecture 4 Topics: Atomic Theory and Structure Chapter 2.1 – 2.5
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John Dalton: Atomic Theory The British chemist John Dalton (1766-1844) is credited with the formulation of the atomic theory of matter . Atomic theory offers an explanation f e structure of atter terms of of the structure of matter in terms of combinations of very small particles. There are four postulates that define Dalton’s theory.
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Dalton’s Postulates of Atomic Theory Postulate #1: All matter is composed of indivisible atoms . An atom is an extremely small particle of matter that retains its identity during chemical reactions. Image of iodine atoms on a platinum surface nanometers
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Scanning Tunneling Microscope These are iron atoms arranged in a circle on a copper surface using a scanning tunneling microscope (STM) Source: IBM Research Division, Almaden Research Center; research done by Donald M. Eigler and coworkers. probe. STM uses a very fine tip (only an atom wide) and electric current to measure 3-D profiles of surfaces.
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Overhead View of the Atomic Iron Ring STM can see features <0.3 nanometer (3 x 10 -10 meters) in size.
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Construction of the “Quantum Corral” Here are various stages in constructing the ring of Fe atoms. ore information More information and images can be found at: http://www.almaden .ibm.com/vis/stm/gal lery.html
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Chemical Structure of a Molecule Resolved by Atomic Force Microscopy (AFM) Chemists are now able to “see” individual atoms in molecules! Pentacene Model STM Image Science 28 August 2009: Vol. 325. no. 5944, pp. 1110 - 1114 http://www.sciencemag.org/cgi/content/full/325/5944/1110 AFM Image AFM Image
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Dalton’s Postulates of Atomic Theory Postulate #2: An element is a type of matter composed of only one kind of atom, each atom of a given element having the same properties. Mass is one such roperty. Thus the property. atoms of a given element have a characteristic mass.
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Dalton’s Postulates of Atomic Theory Postulate #3: A compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions. The relative numbers of any two kinds of atoms in compound occur in simple ratios. a compound occur in simple ratios. Water (H 2 O), for example, consists of hydrogen and oxygen in a 2 to 1 ratio. This is the Law of Multiple Proportions .
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Reaction of Sodium and Chlorine Sodium (Na) + Chlorine (Cl) Sodium Chloride (NaCl) Chlorine Sodium
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An atomic symbol is a one– or two–letter notation used to represent an atom corresponding to a particular element. Typically, the atomic symbol consists of the first tter, capitalized, from the name of that letter, capitalized, from the name of that element, sometimes with an additional letter from the name in lowercase. Other symbols are derived from the name in
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CHE_106_Lecture4_2009 - Chemistry 106 Lecture 4 Topics...

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