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CHAPTER 24 Nuclear Energy. I. Radioactivity (p.674-683). A. Definitions. Radioactivity emission of high-energy radiation from the nucleus of an atom Nuclide nucleus of an isotope Transmutation process of changing one element into another via nuclear decay. B. Types of Radiation.
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CHAPTER24 Nuclear Energy I. Radioactivity (p.674-683)
A. Definitions • Radioactivity • emission of high-energy radiation from the nucleus of an atom • Nuclide • nucleus of an isotope • Transmutation • process of changing one element into another via nuclear decay
B. Types of Radiation • Alpha () • helium nucleus paper 2+ • Beta-minus (-) • electron lead 1- • Gamma () • high-energy photon concrete 0
C. Nuclear Decay • Why nuclides decay… • to obtain a stable ratio of neutrons to protons Stable Unstable (radioactive)
C. Nuclear Decay TRANSMUTATION • Alpha Emission • Beta Emission
Example Half-lives polonium-194 0.7 seconds lead-212 10.6 hours iodine-131 8.04 days carbon-14 5,370 years uranium-238 4.5 billion years D. Half-life • Half-life (t½) • time it takes for half of the nuclides in a sample to decay
D. Half-life • How much of a 20-g sample of sodium-24 would remain after decaying for 30 hours? Sodium-24 has a half-life of 15 hours. GIVEN: total time = 30 hours t1/2 = 15 hours original mass = 20 g WORK: number of half-lives = 2 20 g ÷ 2 = 10 g (1 half-life) 10 g ÷ 2 = 5 g (2 half-lives) 5 g of 24Na would remain.