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Of the elements with atomic numbers 1 to 92, all but four (technetium, promethium, astatine, and francium) occur in easily detectable quantities on earth, having stable, or very long half life isotopes, or are created as common products of the decay of uranium.
All of the elements with higher atomic numbers, however, have been first discovered artificially, and other than plutonium and neptunium, none occur naturally on earth. They are all radioactive, with a half-life much shorter than the age of the Earth, so any atoms of these elements, if they ever were present at the earth's formation, 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 atomic weapons. The Np and Pu generated are from neutron capture in uranium ore with two subsequent beta decays (238U → 239U → 239Np → 239Pu).
Those that can be found on earth now are artificially generated synthetic elements, via nuclear reactors or particle accelerators. The half lives of these elements show a general trend of decreasing with atomic number. There are exceptions, however, including dubnium and several isotopes of curium. Further anomalous elements in this series have been predicted by Glenn T. Seaborg, and are categorised as the “island of stability.”
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 is a source of controversy.
Additional recommended knowledge
Discovery and naming of transuranium elements
The majority of the transuranium elements were produced by three groups:
List of the transuranic elements
*The existence of these elements has been confirmed, however the names and symbols given are provisional as no names for the elements have been agreed on.
Super-heavy atoms, (super heavy elements, commonly abbreviated SHE), are the transactinide elements beginning with rutherfordium (atomic number 104). They have only been made artificially, and currently serve no useful purpose because their short half-lives cause them to decay after a few minutes to just a few milliseconds, which also makes them extremely hard to study.
Super-heavy atoms have all been created during 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, for example the nuclear fusion of californium-249 and carbon-12 creates rutherfordium. These elements are created in quantities on the atomic scale and no method of mass creation has been found.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Transuranium_element". A list of authors is available in Wikipedia.|