APnuclearchemlecturekotz - 1 Radioactivity : The...

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Unformatted text preview: 1 Radioactivity : The spontaneous emission of alpha, beta, or gamma rays (or other particles) by disintegration of the nuclei of atoms. Radioactive decay : The disintegration of an unstable atomic nucleus by spontaneous emission of radiation Radioactivity occurs at the nuclear level of the atom. Radioactive decay can occur naturally or can be induced ( artificial transmutation ) Nuclear Chemistry e 1 He 4 2 High energy EM radiation In writing a process for radioactive decay: All mass and charge must be conserved Unlike chemical reactions, the type of atom (element) isnt necessarily conserved (because it is changed into some other element) Ex: Determine the missing isotope: Visual Example: U He Pu 235 92 4 2 239 94 + ? 1 10 6 + + e C X A Z For subatomic particles, the subscript is the charge and the superscript is the mass in amu Why does radioactivity occur? Mainly because of instability in the nucleus having to do with the ratio of neutrons to protons, Also written as N/Z p n 1 1 1 + The greatest percentage of stable elements have even numbers of both protons and neutrons. Bismuth (Z=83) is the last occurring element with a stable isotope (Bi-209). Uranium is the last naturally occurring element. These decays increase neutrons and decrease protons Alpha emissions decrease overall mass Increase protons and decrease neutrons What is radioactivity used for?-Medical tracers (e.g. I-131 used in thyroid therapy)-Agricultural and municipal tracers (e.g. tracing breaks in a water pipe)-Energy (e.g. fission reactors)-Weaponry (nuclear bombs)-Dating archeological artifacts (e.g. C-14 dating)-Planetary dating (e.g. age of the Earth from U-238 samples) What types of radioactive decay can occur? 2 Alpha Decay Beta Decay Positron Emission Electron Capture In Summary:-If the mass of an isotope is greater than the average mass of that element (listed on the periodic table) then stability is generally achieved through...
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This note was uploaded on 12/07/2011 for the course CHEM 100 taught by Professor Feebeck during the Fall '10 term at Purdue University-West Lafayette.

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APnuclearchemlecturekotz - 1 Radioactivity : The...

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