Radiocarbon datingAND

Uranium dating-Lou Kimberly L. Colon

-Kaye Esperanza Elizalde-Bunny Grace Escollar

• Another different use of radioactivity is radioactive dating. Radioisotopes decay, yielding their decay products.

• Using the decay curve and the isotope’s known half-life, the age of the sample can be estimated. Radioisotopes are also called as nuclear clocks.

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Uranium Dating

• It is used to determine the age of the earth, the moon or the solar system.

• Uranium238 , Uranium 235, Th232, K40, and Rb87 are used.

• With this method, scientists have estimated the age of the oldest rock on Earth to be 4 billion years

• uranium dating is a radiometric dating technique which compares two isotopes of uranium (U) in a sample: 235U and 238U.235U/238U dating is one of several radiometric dating techniques exploiting the uranium radioactive decay series, in which 238U undergoes 14alpha and beta decay events while decaying to the stable isotope 206Pb and 207Pb.

For example:

• The half life of 238 Uranium is 4.5 X 10 raised to 8 years while that of U235 is a little shorter. Both of them decay into stable isotopes of lead: 238U to be 206Pb and 235U to 207Pb. Thus, any rock that contains uranium will be rich in 206Pb and 207Pb.

• Using the same technique, the age of the earth has been estimated to be about 4.5 billion years .

• Rocks and soil from the moon when examined using the 207Pb-206Pb method, they found out that the age of the rocks in the moon are about 4.6 billion years.

• Since uranium has a very long life,, it is used to measure the age of the older objects in the earth such as rocks and soil.

Rock from the Moon

Carbon Dating

•Uses the decay of the carbon-14 isotope. The half-life of carbon-14 is 5730 years. ]

• Radiocarbon dating (sometimes simply known as carbon dating) is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years

• One of the most frequent uses of radiocarbon dating is to estimate the age of organic remains from archaeological sites.

• When plants fix atmospheric carbon dioxide (CO2) into organic material during photosynthesis they incorporate a quantity of 14C that approximately matches the level of this isotope in the atmosphere. After plants die or they are consumed by other organisms the 14C fraction of this organic material declines at a fixed exponential rate due to the radioactive decay of 14C

• The technique of radiocarbon dating was developed by Willard Libby and his colleagues at the University of Chicago in 1949. . Libby estimated that the steady state radioactivity concentration of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram.. He first demonstrated the accuracy of radiocarbon dating by accurately estimating the age of wood from an ancient Egyptian royal barge for which the age was known from historical documents.

• The age of artifacts from archaeological sites can be determined using carbon-dating techniques.

• The oldest caves in Palawan were found to be 40,000 years.