Radiometric dating is often referred to as “radioactive dating” and “carbon dating,” though many different types of isotopes can be used to identify an object’s age.
While not all objects have the same isotopes, both living and nonliving objects have some sort of decaying, radioactive isotope that can be used based on known decay rates. An isotope of some sort is located and isolated within an object.
When an isotope decays, it often becomes a different kind of element altogether.
Because this new element (decay product) remains on or within the object, scientists can easily determine how old the object is. A mass spectrometer is a fundamental device in any radiometric dating experiment.
The dating equation used for K-Ar is: Carbon Dating Radiocarbon dating is different than the other methods of dating because it cannot be used to directly date rocks, but can only be used to date organic material produced by once living organisms.
Radiometric dating is a process of identifying the age of a material based on known half-lives of decaying radioactive materials found in both organic and inorganic objects.
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.
Such trapped Ar is not problematical when the age of the rock is in hundreds of millions of years.
Thus, if we start out with 1 gram of the parent isotope, after the passage of 1 half-life there will be 0.5 gram of the parent isotope left.
After the passage of two half-lives only 0.25 gram will remain, and after 3 half lives only 0.125 will remain etc.
Mass spectrometers can be used to measure isotopic samples as small as one 1 nanogram.
Mass spectrometers are made up of an ion generator, analyzer, and several detectors.
The only problem is that we only know the number of daughter atoms now present, and some of those may have been present prior to the start of our clock. The reason for this is that Rb has become distributed unequally through the Earth over time.