Unit 8 Ch. 25 Half–Life Fission Fusion ABClark-Grubb

Half - Life The time required for one-half of nuclei of a radioisotope sample to decay to products.

Example: Radon–222 emits alpha radiation and decays with a half-life of 3.8 days. Assume you have a mass of 916 g Radon. How long is 4 half-lives? 3.8 days x 4 = 15.2 days How many grams of the isotope remain at the end of 4 half-lives? In 31 days, how many half-lives will Radon-222 go through? 31 days ÷ 3.8 days = 8.2 half-lives ½ ½ ½ ½ 916 g x x x x = 57.25 g left

Nuclear Fission The splitting of a nucleus into smaller fragments U-235 and Pu-239 are the only fissionable isotopes Fission can release enormous amounts of energy Fission can be controlled so energy is released more slowly (nuclear reactors)

Nuclear Fusion Occurs when nuclei combine to produce a nucleus of greater mass Release much more energy than a fission reaction Using fusion as an energy source is appealing but not practical. . .too difficult to achieve the high temperatures needed to start the reaction

Assignment Complete: Page 806 7,8 Page 808 12b-d,13 Page 822 51