A radiometric dating technique uses the decay of

De Hevesy also is credited with discovering the technique of neutron activation analysis, in which samples are bombarded by neutrons in a nuclear reactor or from a neutron generator, and the resulting radioactive isotopes are measured, allowing the analysis of the elemental composition of the sample.

Seaborg and coworkers went on to discover many more new elements and radioactive isotopes and to study their chemical and physical properties.

At the present, nuclear chemists are involved in trying to discover new elements beyond the 112 that are presently confirmed and to study the chemical properties of these new elements, even though they may exist for only a few thousandths of a second.

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.

Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin.

Today, many of these same chemical separation techniques are being used by nuclear chemists to clean up radioactive wastes resulting from the fifty-year production of nuclear weapons and to treat wastes derived from the production of nuclear power.

In 1940, at the University of California in Berkeley, Edwin Mc Millan and Philip Abelson produced the first manmade element, neptunium (Np), by the bombardment of uranium with low energy neutrons from a nuclear accelerator.

De Hevesy did not succeed in this task (we now know that radium-D is the radioactive isotope Pb to measure the solubility of lead salts—the first application of an isotopic tracer technique.

De Hevesy went on to pioneer the application of isotopic tracers to study biological processes and is generally considered to be the founder of a very important area in which nuclear chemists work today, the field of nuclear medicine.

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.

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