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Unit 14: Nuclear CHemistry

Unit 14: Nuclear CHemistry. Section 3: Radioactive Decay and Half-Life. Radioactive Decay. The spontaneous emission of rays or particles from certain nuclei as they “decay,” such as Uranium . These rays or particles are called nuclear radiation . They come in three types:

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Unit 14: Nuclear CHemistry

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  1. Unit 14: Nuclear CHemistry Section 3: Radioactive Decay and Half-Life

  2. Radioactive Decay • The spontaneous emission of rays or particles from certain nuclei as they “decay,” such as Uranium. • These rays or particles are called nuclear radiation. • They come in three types: • Alpha Radiation: Helium nucleus; 2+ Charge; Low power (0.05 mm body tissue) • Beta Radiation: electron; 1- Charge; Moderate power (4 mm body tissue) • Gamma Radiation: electromagnetic wave; neutral charge; High Power (penetrates entire body easily)

  3. Alpha Decay of Uranium

  4. Half-Life • While the process is spontaneous, it is not instantaneous… it takes time! • The time required for HALF of the atoms of a radioactive substance to decay is called a half-life.

  5. Carbon-Dating!! C-14

  6. Example: Fluorine-18 18 9 • Fluorine 18 ( F) has a half-life of 110 seconds. This material is used extensively in medicine. The hospital laboratory begins the day with 10 grams of F… 18 9

  7. How many half-lives of f-18 occur in 11 minutes (660 sec)? 1 half-life = 110 seconds 660 seconds 110 seconds = 6 half-lives

  8. How much of the 10-gram sample would be left after 11 minutes? • 6 half-lives = 10 divided in half, 6 times • 10/2 = 5 grams • 5/2 = 2.5 grams • 2.5/2 = 1.25 grams • 1.25/2 = 0.625 grams • 0.625/2 = 0.3125 grams • 0.3125/2 = 0.15625 grams After 11 minutes, only 0.16 g of the 10 g sample remain!!!!!!

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