Radiometric dating uses what isotopes

29 Jan

Nuclear chemists were involved in the chemical purification of plutonium obtained from uranium targets that had been irradiated in reactors.

While the common perception is that nuclear chemistry involves only the study of radioactive nuclei, advances in modern mass spectrometry instrumentation has made chemical studies using stable, nonradioactive isotopes increasingly important.

There are essentially three sources of radioactive elements.

Primordial nuclides are radioactive elements whose half-lives are comparable to the age of our solar system and were present at the formation of Earth.

These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium.

Once an organism is dead, however, no new carbon is actively absorbed by its tissues, and its carbon 14 gradually decays.

Libby thus reasoned that by measuring carbon 14 levels in the remains of an organism that died long ago, one could estimate the time of its death.

Using an electrometer invented by her husband Pierre and his brother Jacques that measured the electrical conductivity of air (a precursor to the Geiger counter), she was able to show that thorium also produced these rays—a process that she called radioactivity.

Through tedious chemical separation procedures involving precipitation of different chemical fractions, Marie was able to show that a separated fraction that had the chemical properties of bismuth and another fraction that had the chemical properties of barium were much more radioactive per unit mass than the original uranium ore.

In Germany in 1938, Otto Hahn and Fritz Strassmann, skeptical of claims by Enrico Fermi and Irène Joliot-Curie that bombardment of uranium by neutrons produced new so-called transuranic elements (elements beyond uranium), repeated these experiments and chemically isolated a radioactive isotope of barium.

Unable to interpret these findings, Hahn asked Lise Meitner, a physicist and former colleague, to propose an explanation for his observations.