Transuranium element


The transuranium 'elements' are the chemical elements with atomic number greater than 92, which is the atomic number of uranium. All of them are radioactively unstable and decay into other elements. They are synthetic and none occur naturally on Earth, except for neptunium and plutonium which have been found in trace amounts in naturally occurring uranium ore.

Overview

Of the elements with atomic numbers 1 to 92, most can be found in nature, having stable isotopes or very long-lived radioisotopes, or existing as common decay products of the decay of uranium and thorium. The exceptions are technetium, promethium, astatine, and francium; all four occur in nature, but only in very minor branches of the uranium and thorium decay chains, and thus all except francium were first discovered by synthesis in the laboratory rather than in nature.
All elements with higher atomic numbers have been first discovered in the laboratory, with neptunium and plutonium later discovered in nature. They are all radioactive, with a half-life much shorter than the age of the Earth, so any primordial atoms of these elements, have long since decayed. Trace amounts of neptunium and plutonium form in some uranium-rich rock, and small amounts are produced during atmospheric tests of nuclear weapons. These two elements are generated by neutron capture in uranium ore with subsequent beta decays.
All elements beyond plutonium are entirely synthetic, at least on Earth; they are created in nuclear reactors or particle accelerators. The half-lives of these elements show a general trend of decreasing as atomic numbers increase. There are exceptions, however, including several isotopes of curium and dubnium. Some heavier elements in this series, around atomic numbers 110–114, are thought to break the trend and demonstrate increased nuclear stability, comprising the theoretical island of stability.
Transuranic elements are difficult and expensive to produce, and their prices increase rapidly with atomic number. As of 2008, the cost of weapons-grade plutonium was around $4,000/gram, and californium exceeded $60,000,000/gram. Einsteinium is the heaviest element that has been produced in macroscopic quantities.
Transuranic elements that have not been discovered, or have been discovered but are not yet officially named, use IUPAC's systematic element names. The naming of transuranic elements may be a source of controversy.

Discoveries

So far, essentially all transuranium elements have been discovered at four laboratories: Lawrence Berkeley National Laboratory in the United States, the GSI Helmholtz Centre for Heavy Ion Research in Germany, RIKEN in Japan, and the Joint Institute for Nuclear Research in Russia.
Superheavy elements, usually refer to the transactinide elements beginning with rutherfordium. They have only been made artificially and currently serve no practical purpose because their short half-lives cause them to decay after a very short time, ranging from a few hours to just milliseconds, which also makes them extremely hard to study.
Superheavies have all been created since the latter half of the 20th century and are continually being created during the 21st century as technology advances. They are created through the bombardment of elements in a particle accelerator, in quantities on the atomic scale, and no method of mass creation has been found.

Applications

Transuranic elements may be used to synthesize superheavy elements. Elements of the island of stability have potentially important military applications, including the development of compact nuclear weapons. The potential everyday applications are vast; americium is used in devices such as smoke detectors and spectrometers.