Outline:4/20/07 Today: Chapter 22 (cont’d) Nuclear Chemistry - Nuclear Applications… Fission devices, Radiodating, Nuclear medicine... è Chem seminar 4pm è One week to go… è Practice final exams online…

Let do some CAPA questions: #8 – A radioactivity counter gives a reading of 385 counts per minute, for a 15.1-mg sample of cobalt(II)chloride, partially enriched with 60 Co (half-life = 5.26 yr). What percentage of the cobalt atoms in this sample are 60 Co? n Calculate the decays per minute you expect from pure 60 CoCl 2 n Divide 385 cpm by the expected to get percentage…

Let do some CAPA questions: #8 – half-life of 5.26 years: What is k? k =  /min = k t 1/2 k = /y Units of 1/min…  1 y / 525,600 min What is N 0 ? g CoCl 2  1 mol/131 g  6.022e23 = 6.941e19 atoms 60 Co

Let do some CAPA questions: #8 – N = N 0 e  kt t = 1 min N = e19 N = 6.941e19 exp (  ) What is N 0 -N? 1.741e13 Therefore, not much 60 Co present: (385 / 1.741e13)  100% = 2.212e-9 %

Nuclear Reactions: Radon n n Natural series: Uranium  238 U   Th  234 Th    Pa 238 U  234 Pa    U  234 U   Th  230 Th   Ra  226 Ra   Rn  222 Rn   Po                Pb

Nuclear Reactions: Radon

Nuclear Reactions: Fission

Nucleosynthesis…

Radiodating… e.g. : If 10.0 g of Kennewick Man bone has 34.6 dpm of 14 C, and a present-day 10.0 g bone has dpm, how old is Kennewick Man?  N/N 0 = e  k t or ln(N/N 0 ) =  k t  ln(34.6/103.7) =  k t 1/2 t = 9080 yrs

Medical Diagnosis & Treatment: Nuclear Medicine X-rays/CAT, Tracers, PET, beam therapy, brachytherapy

Why nuclear effects? High energy, sub-atomic (small) : highly penetrating High energy: highly ionizing 

What effect does it have on biology? Mutation….mutagenisis, Cancer….tumorigenisis. Does it make atoms radioactive? No…ionization is a chemical process, not a nuclear process. Consider Food Irradiation….

Handout: Benign Hamburger + List of questions to be answered in class on Monday Everybody has a different selection of questions. Read the “case”. Look for answers in the textbook, look for references in the library/on the web.