Lec-03-Chap-02-1P

Lec-03-Chap-02-1P - Lecture 03 Atoms and Elements Atomic...

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Lecture 03 Atoms and Elements Atomic Structure and Subatomic Particles 2.1 The Nuclear Atom 2.2 Sizes of Atoms and Atomic Units 2.3 Uncertainty and Significant Figures 2.4 Atomic Numbers and Mass Numbers 2.5 Lecture 03, Knowledge and Skills • Know the basic types of radioactivity • Know about the historic experiments that established the nature of atoms • Know the atomic subparticles • Know the nuclear model of the atom • Know and work with units • Understand the meaning of significant figures • Calculate with significant figures • Understand and work with atomic numbers and mass numbers Atomic Structure and Subatomic Particles • Atoms are composed of subatomic particles: • electron (e - ), proton (p + ) and neutron (n 0 ) • Key discoveries: Radioactivity Radioactivity • Becquerel (1896) • Uranium ore emits rays that “fog” a photographic plate • Marie and Pierre Curie (1898) • Marie Curie called the phenomenon radioactivity radioactivity Radiation Summary • Alpha Radiation • composed of 2 protons and 2 neutrons • creates element with atomic number 2 lower • Beta Radiation • composed of a high energy electron which was ejected from the nucleus • “neutron” converted to “proton” • creates element with atomic number higher by 1 • Gamma Radiation • energy released from nucleus as the nucleus changes from higher to lower energy levels • no mass • no charge Electrons • Electric and magnetic fields deflect the beam • Gives mass/charge of e - = ± 5 .60 x 10 -9 g/C • Coulomb (C) = SI unit of charge • Joseph John Thomson (1897) discovered the e - : • “Cathode rays” • Travel from cathode (-) to anode (+) • Negative charge (e ± ) • Emitted by cathode metal atoms Electrons Millikan Oil Drop Experiment Charge on each droplet was: n ( ± 1 .60 x 10 -19 C) with n = 1, 2, 3,… n (e - charge) • Modern value = ± 1 .60217653 x 10 -19 C = ± 1 “atomic units” These experiments give:
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Lec-03-Chap-02-1P - Lecture 03 Atoms and Elements Atomic...

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