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Published byJeremy Porter Modified over 9 years ago
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Half-life
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Half-Life - the time required for one half of a sample of a radioisotope to decay, while the other half remains unchanged Half-lives vary greatly depending on the element Fractions of a second (lithium-5 324 X 10 -24 ) Billions of years (Uranium-238 4.5 billion years
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Half-life Unlike chemical reaction rates which change depending upon conditions Rate of nuclear decay is constant
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Calculating half-lives elapsed Half-lives elapsed= Total time of decay/half- life 1 gram sample of iridium-182 Iridium half-life= 15 min. 45 min. have elapsed 45 min. / 15 min = 3 half lives After 45 min. iridium would have been reduced by half 3 times.
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Calculating… ½ X ½ X ½ = 1/8 1/8 x 1 gram=.0125 grams of iridium-182
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Radiocarbon Dating In radioactive dating, the age of an object is determined by comparing an objects carbon-14 levels with carbon-14 levels in the atmosphere Half-life carbon-14 is 5,730 years If the fossil has half the ratio of the atmosphere then the organism lived 5,730 years ago
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