Rubidium strontium age dating

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Potassium-Argon dating: The element potassium (symbol K) has three nuclides, K39, K40, and K41. K40 can decay in two different ways: it can break down into either calcium or argon.

The ratio of calcium formed to argon formed is fixed and known.

An atom with the same number of protons in the nucleus but a different number of neutrons is called an isotope.

For example, uranium-238 is an isotope of uranium-235, because it has 3 more neutrons in the nucleus.

At this point the fraction of Rb87 = Sr87 = 0.500; at half life = 2.00, Rb87 = 25% and Sr87 = 75%, and so on. 131, Strahler, Science and Earth History: Points are taken from these curves and a plot of fraction Sr-87/Sr-86 (as ordinate) vs. It turns out to be a straight line with a slope of -1.00.Strontium-86 is a stable element that does not undergo radioactive change.In addition, it is not formed as the result of a radioactive decay process.Therefore the amount of argon formed provides a direct measurement of the amount of potassium-40 present in the specimen when it was originally formed.Because argon is an inert gas, it is not possible that it might have been in the mineral when it was first formed from molten magma.

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