

There are about 730 radionuclides with halflives longer than 60 minutes (see list of nuclides).With the longest half lives are the 32 primordial radionuclides that have survived from the creation of the Solar System.Libby received the Nobel Prize in Chemistry for his work in 1960.The radiocarbon dating method is based on the fact that radiocarbon is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen.2) To familiarize students with the concept of halflife in radioactive decay.3) To have students see that individual runs of statistical processes are less predictable than the average of many runs (or that runs with relatively small numbers involved are less dependable than runs with many numbers).The object's approximate age can then be figured out using the known rate of decay of the isotope.


By definition, D* = N1) (2) Now we can calculate the age if we know the number of daughter atoms produced by decay, D* and the number of parent atoms now present, N.It wasn't until well into the 20th century that enough information had accumulated about the rate of radioactive decay that the age of rocks and fossils in number of years could be determined through radiometric age dating.This activity on determining age of rocks and fossils is intended for 8th or 9th grade students.Prior to 1905 the best and most accepted age of the Earth was that proposed by Lord Kelvin based on the amount of time necessary for the Earth to cool to its present temperature from a completely liquid state.Although we now recognize lots of problems with that calculation, the age of 25 my was accepted by most physicists, but considered too short by most geologists. Recognition that radioactive decay of atoms occurs in the Earth was important in two respects: Principles of Radiometric Dating Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential (Energy) barrier which bonds them to the nucleus.The range of the halflives of radioactive atoms have no known limits and span a time range of over 55 orders of magnitude.
