1. CHAPTER 24 Nuclear Energy I. Radioactivity (p.674-683) I. Radioactivity (p.674-683)

2. 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

3. B. Types of Radiation Alpha ( ) helium nucleus paper 2+ Beta-minus ( -) electron 1- lead Gamma ( ) high-energy photon 0 concrete

4. C. Nuclear Decay Why nuclides decay… to obtain a stable ratio of neutrons to protons Stable Unstable (radioactive)

5. C. Nuclear Decay Alpha Emission Beta Emission TRANSMUTATIONTRANSMUTATION

6. D. Half-life Half-life (t ½ ) time it takes for half of the nuclides in a sample to decay Example Half-lives polonium-1940.7 seconds lead-21210.6 hours iodine-1318.04 days carbon-145,370 years uranium-2384.5 billion years

7. 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 t 1/2 = 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 24 Na would remain.