chem 1151 ch 2

chem 1151 ch 2 - Chem 1151 Chapter 2 Atoms and Elements I...

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Unformatted text preview: Chem. 1151, Chapter 2 Atoms and Elements I. Brief History Of The Atom 500 BC: Democritus: matter is `particle'like. (Atoms) 400 BC: Aristotle, Plato: No particles. Matter made of fire, water, earth, air. 400 BC 1600 AD: Alchemists: Used symbols, developed lab techniques, attempted to turn base metals into gold, prepared `elixir' of life. 1700. Lavosier: Law of Conservation of Mass 1700. Proust: Law of Definite Proportion 1800. John Dalton: Law of Multiple Prop. and the Atomic Theory 1900. J.J. Thomson: characterized electron 1900. William Wien: proton 1911. Ernest Rutherford: nucleus of atom 1913. Niels Bohr: planetary model of atom 1932. James Chadwick: confirmed neutron II. Basic Laws of Matter: overhead III. John DaltonAtomic Theory (used theory to explain the 3 laws) p.43 Matter made of indivisible particles called atoms. All atoms of 1 element are alike by mass and different from those of every other element. Atoms join together in small whole number ratios. Chemical change is rearrangement of atoms IV. Structure of Atom A. Electron: J.J.Thomson: Cathode raysbeam of particles travelling from cathode () to anode (+). Thus, have negative charge. Determined charge to mass ratio. Millikan: "oil drop" experiment. Determined magnitude of charge and mass of electron. B. Proton: canal rays positive particle. Neutron: neutral particle. C. Thomson: "Plum Pudding" model of atom: Electrons in a sea of positive charge. D. Nuclear Atom: 1. Rutherford's Gold Foil Experiment. 2. Conclusions: nucleus positively charged nucleus is small, dense core at center of atom Atomic particle summary: Tb. 2.1 E. Atomic Properties 1. Atomic Number (Z) : # of protons Determines identity of atom. 2. Atomic Mass Number (A): average atomic mass rounded to nearest whole number. Sum of protons + neutrons in nucleus. 3. Nuclide symbol: A Z X ...
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