l23 - The nucleus Reminder for the holidays Radiactive...

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The nucleus Radiactive decay Radioactive dating Dating the earth Patterson: lead Reminder for the holidays A reminder: not everyone is a physicist. Act appropriately. http://www.xkcd.com/660/
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The nucleus Radiactive decay Radioactive dating Dating the earth Patterson: lead The nucleus: review The nucleus is made up of protons and neutrons. Nuclear density is quite constant constant, so R = R 0 A 1 / 3 with R 0 1 . 2 × 10 - 15 m. The number of protons Z determines electron orbitals, thus chemical behavior, thus element name and position in periodic table. But there are isotopes with the same proton number Z but different neutron number N = A Z . We write these as A Element, as in 14 C and 12 C for carbon with 8 or 6 neutrons, respectively. Some isotopes are stable, while others are not. Those that are unstable can undergo alpha decay (emission of 4 2 He nuclei), beta decay (emission of electrons or positrons), and gamma decay (emission of >100 keV photons). Δ E = Δ mc 2 applies. Number of nuclei remaining goes like N = N 0 e - λ t , with λ = ln 2 / t 1 / 2 . Also A = λ N , with a common unit being the Curie: 1 Ci=3 . 7 × 10 10 decays/second.
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The nucleus Radiactive decay Radioactive dating Dating the earth Patterson: lead Decay chains We’ve outlined the basic single-step radioactive decay processes. In fact, radioactive isotopes often involve a series of decays, and they can include branching: Three natural heavy-element decay chains wind up producing different isotopes of lead: 238 92 U 206 82 Pb ( t 1 / 2 = 4 . 47 × 10 9 years) 235 92 U 207 82 Pb ( t 1 / 2 = 7 . 04 × 10 8 years) 232 90 Th 208 82 Pb ( t 1 / 2 = 1 . 41 × 10 9 years)
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The nucleus Radiactive decay Radioactive dating Dating the earth Patterson: lead An example decay chain The half-life of 235 92 U 207 82 Pb is t 1 / 2 = 7 . 04 × 10 8 years See also Serway Fig. 13.21.
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The nucleus Radiactive decay Radioactive dating Dating the earth
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This note was uploaded on 05/28/2011 for the course PHY 251 taught by Professor Rijssenbeek during the Fall '01 term at SUNY Stony Brook.

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l23 - The nucleus Reminder for the holidays Radiactive...

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