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Download Chemistry 102B What`s in an atom? Before “Chemistry” Other Early
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Before “Chemistry” • Alchemy/Alchemists - a pseudoscience built around trying to turn cheap metals into GOLD! (400 B.C.-1400 A.D.) • Metallurgy – systematic extraction of metals from ores laid some groundwork for modern chemistry. (1500s) • The first “chemist” was Robert Boyle who worked on pressure and volume of gases and postulated that elements could not be separated into simpler substances. (1660s) Chemistry 102B What’s in an atom? January 22, 2007 Other Early Chemists John Dalton’s Atomic Theory • Antoine Lavoisier (late 1700s) – carefully weighed reactants and products of combustion. Developed the “Law of conservation of Mass”. • Joseph Proust (early 1800s) – discovered that a given compound always contained the same proportions of certain elements by mass. “Law of Definite Proportions” • John Dalton (early 1800s) – noted that elements that combined to form more than one kind of compound, did so in proportions of integers by mass. “Law of Multiple Proportions” 1. Each element is made up of tiny particles called atoms. 2. Atoms of a given element are identical, atoms of different elements are different. 3. Chemical compounds are formed when atoms of 2 or more elements combine w/ each other. A given compound always has the same relative numbers and types of atoms. 4. Chemical reactions involve reorganization of the atoms, but not atoms are destroyed or created. “Law of conservation of mass” Practice Problem J. J. Thomson, Cathode Ray Tube A B C Which box displays a i. a gaseous compound and gaseous element A and B ii. a solid element and a gaseous compound C 1 Robert Millikan, Charge Oil Droplets Plum Pudding Model of the Atom Electrons dispersed evenly Ernest Rutherford, Gold Foil Experiment Modern View of Atomic Structure (Page 5) 10-13 cm http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/006_RUTHERFORD.MOV Nuclear Particles (Page 9) Particle • Electrons • Protons • Neutrons 10-8 cm If a nucleus were the size of a marble, the atom would be the size of Memorial Stadium. Alkali metals Alkaline earth metals Noble gases Halogens Mass Charge -31 9.10939 x 10 kg 11.67265 x 10-27 kg 1+ -27 1.67495 x 10 kg None Mass number Atomic number A Z X Element symbol Mass number, A, = total number of protons and neutrons Atomic number, Z, = number of protons 2