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Published byGwenda Wilson Modified over 6 years ago
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Radioactive Dating Calculating the age of a sample based
on the remaining amount of a radioactive isotope the sample contains. By calculating the amount of uranium-238 and thorium-232, this meteorite was dated to be billion years old, give or take 2 billion.
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How is Relative Dating Different?
Date fossils relative to their position in rock No info on age in years
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Half-life The amount of time it takes for half of radioactive atoms in a sample to decay. Different elements have different half lives and are used to date samples of various time periods
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Used to date fossils and artifacts such as the “Ice Man”
Radiocarbon Dating Used to date fossils and artifacts such as the “Ice Man” found to be 5500 years old
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Radiocarbon dating Method developed by William Libby at U. of Chicago
Won Nobel Prize in 1960 Also worked on Manhattan Project in 1940’s Peaceful application of radioactive elements!
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How does it work? Carbon-14 is taken in by living things
After organism dies, C-14 decays to form N-14 (escapes into air) C-12 is common carbon isotope found in all living things and does NOT decay because it is stable!
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How does it work? continued
Half life of C-14 is 5,730 years. Ratio of C-14 to C-12 in living things is 1 to 1 trillion. Materials are tested to see ratio of C-14 to C-12 and date can be determined
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Radiocarbon Dating
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Sample problems: What is the half life of a substance if 1/64th of the original amount remains after 1,500 years? An isotope of cesium (cesium-137) has a half -life of 30 years. If 1.0 mg of cesium-137 disintegrates over a period of 90 years, how many mg of cesium-137 would remain?
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