chap4 - Chap 4 Chem 10 1. Radioactivityradioactive decay-...

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1 Chap 4 Chem 10 1. Radioactivity- radioactive decay- unstable nuclei form different elements. Need to balance total mass of particles but not atoms. Types of decay. Radiation Mass Charge Identity velocity Penetrating Power Alpha( a ) 4 2+ He 2+ 0.1c Very low Beta( b ) 0.00055 1- e’ < 0.9c moderate Gamma( g ) 0 0 High energy photon c Extremely high A) Ex. Alpha decay Mass number: 234 4 + 230 Atomic number: 92 2 + 90 B) Beta decay Mass number: 235 0 + 235 U 234 92 He 4 2 + 230 90 Th U 235 92 b 0 -1 + 235 93 Np U 238 92 He 4 2 + 234 90 Th
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2 Atomic number: 92 -1 + 93 C) gamma decay no change in mass number or atomic number. Ex Complete the following equations. Ex write the alpha decay of thorium-225. Ex A radioactive isotope decays to give an alpha particle and bismuth-211. What was the original isotope? 2. Half life- radioactive isotope period in which one-half of the original number of atoms undergoes decay. Fraction remaining = 1/2 n n = number of half lives Ex. Tritium a radioactive isotope of hydrogen, has a half life of 12.3 years. If you begin with 1.5 mg of the isotope, how many milligrams remain after 49.2 years? Au 179 79 Ir 175 77 + ? Ne 23 10 Na 23 11 + ? ? = He 4 2 ? = e 0 -1 Th 225 90 Ra 221 88 + He 4 2 At 215 85
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3 49.2/12.3 years = 4.00 half lives 1.5 mg x 1/2 x 1/2 x 1/2 x 1/2 = 1.5 x 1/16 = 0.094 mg A) carbon-14 dating carbon-14 is made in the upper layers of the atmosphere by bombardment of nitrogen by neutrons from cosmic rays.
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This note was uploaded on 09/02/2011 for the course CHEM 10 taught by Professor Harrison during the Spring '11 term at West Valley.

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chap4 - Chap 4 Chem 10 1. Radioactivityradioactive decay-...

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