Chapter 19 notes

Chapter 19 notes - Chapter 19 Objectives(Nuclear Chemistry...

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Chapter 19 Objectives (Nuclear Chemistry) Spring 2084 1. Background. a) Radioactivity is the emission of particles or radiation from naturally occurring unstable isotopes. i. Bequerel observed this via exposure on film from uranium salts he was studying (he first proposed this exposure was due to x-rays during phosphorescence). ii. Curie discovered this effect in both radium and polonium. b) Recall that elements exist as isotopes differing only in the number of neutrons. U 235 92 U 238 92 92p, 143 n 92 p, 146 n c) All isotopes above atomic number 83 are radioactive. d) There are various types of radioactive emissions. e) There are several reasons why some isotopes are unstable. f) The rate of nuclear decay is independent of temperature and independent of chemical environment. g) The energy changes in nuclear reactions are 10 7 – 10 8 times greater per mol than chemical reactions. h) Very small amounts of mass are converted to huge amounts of energy (E = mc 2 ). i) In balanced nuclear reactions, atomic number and atomic mass number are conserved. 2. Types of Natural Radioactivity. a) Alpha ( He 4 2 ) 2+ emission – very common for atomic # > 83. U 238 92 Th 234 90 + He 4 2 Note: 238 = 234 + 4; 92 = 90 + 2 Alpha emissions are less energetic than beta and gamma emissions – little penetrating power; however, if ingested, it has very high biologic effectiveness (damaging!).
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Chapter 19 Objectives (Nuclear Chemistry) Spring 2084 b) Beta decay. Ra
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Chapter 19 notes - Chapter 19 Objectives(Nuclear Chemistry...

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