The transuranium elements (also known as transuranic elements) are the
chemical elements with
atomic numbers greater than 92, which is the atomic number of
uranium. All of them are
radioactively unstable and decay into other elements. With the exception of
neptunium and
plutonium which have been found in trace amounts in nature, none occur naturally on Earth and they are
synthetic.
Overview
Of the elements with atomic numbers 1 to 92, most can be found in nature, having stable
isotopes (such as
oxygen) or very long-lived
radioisotopes (such as
uranium), or existing as common
decay products of the decay of uranium and
thorium (such as
radon). The exceptions are elements
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 save francium were first discovered by synthesis in the laboratory rather than in nature.
All the 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, 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
nuclear weapons. These two elements are generated from
neutron capture in
uranium ore with subsequent
beta decays (e.g.
238U +
n →
239U →
239Np →
239Pu).
All elements heavier than plutonium are entirely
synthetic; 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.[1]
Heavy 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,[2] and
californium exceeded $60,000,000/gram.[3]Einsteinium is the heaviest element that has been produced in macroscopic quantities.[4]
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.
102.
nobelium, No, named after
Alfred Nobel (1958). The element was originally claimed by a team at the
Nobel Institute in Sweden (1957) – though it later became apparent that the Swedish team had not discovered the element, the LBNL team decided to adopt their name nobelium. This discovery was also claimed by JINR, which doubted the LBNL claim, and named the element joliotium (Jl) after
Frédéric Joliot-Curie (1965). IUPAC concluded that the JINR had been the first to convincingly synthesise the element (1965), but retained the name nobelium as deeply entrenched in the literature.
103.
lawrencium, Lr, named after
Ernest O. Lawrence, a physicist best known for development of the
cyclotron, and the person for whom the
Lawrence Livermore National Laboratory and LBNL (which hosted the creation of these transuranium elements) are named (1961). This discovery was also claimed by the JINR (1965), which doubted the LBNL claim and proposed the name rutherfordium (Rf) after
Ernest Rutherford. IUPAC concluded that credit should be shared, retaining the name lawrencium as entrenched in the literature.
104.
rutherfordium, Rf, named after
Ernest Rutherford, who was responsible for the concept of the
atomic nucleus (1969). This discovery was also claimed by JINR, led principally by
Georgy Flyorov: they named the element kurchatovium (Ku), after
Igor Kurchatov. IUPAC concluded that credit should be shared, and adopted the LBNL name rutherfordium.
105.
dubnium, Db, an element that is named after
Dubna, where JINR is located. Originally named hahnium (Ha) in honor of
Otto Hahn by the Berkeley group (1970). This discovery was also claimed by JINR, which named it nielsbohrium (Ns) after
Niels Bohr. IUPAC concluded that credit should be shared, and renamed the element dubnium to honour the JINR team.
106.
seaborgium, Sg, named after
Glenn T. Seaborg. This name caused controversy because Seaborg was still alive, but it eventually became accepted by international chemists (1974). This discovery was also claimed by JINR. IUPAC concluded that the Berkeley team had been the first to convincingly synthesise the element.
107.
bohrium, Bh, named after the Danish physicist
Niels Bohr, important in the elucidation of the structure of the
atom (1981). This discovery was also claimed by JINR. IUPAC concluded that the GSI had been the first to convincingly synthesise the element. The GSI team had originally proposed nielsbohrium (Ns) to resolve the naming dispute on element 105, but this was changed by IUPAC as there was no precedent for using a scientist's first name in an element name.
108.
hassium, Hs, named after the
Latin form of the name of
Hessen, the German Bundesland where this work was performed (1984). This discovery was also claimed by JINR. IUPAC concluded that the GSI had been the first to convincingly synthesise the element, while acknowledging the pioneering work at JINR.
110.
darmstadtium, Ds, named after
Darmstadt, Germany, the city in which this work was performed (1994). This discovery was also claimed by JINR, which proposed the name becquerelium after
Henri Becquerel, and by LBNL, which proposed the name hahnium to resolve the dispute on element 105 (despite having protested the reusing of established names for different elements). IUPAC concluded that GSI had been the first to convincingly synthesize the element.
113.
nihonium, Nh, named after
Japan (Nihon in
Japanese) where the element was discovered (2004). This discovery was also claimed by JINR. IUPAC concluded that RIKEN had been the first to convincingly synthesise the element.
Superheavy elements, (also known as superheavy atoms, commonly abbreviated SHE) usually refer to the transactinide elements beginning with
rutherfordium (atomic number 104). (Lawrencium, the first 6d element, is sometimes but not always included as well.) 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 a few milliseconds, which also makes them extremely hard to study.[5][6]
Superheavy atoms 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.[5]
Applications
Transuranium elements may be used to synthesize other superheavy elements.[7] Elements of the island of stability have potentially important military applications, including the development of compact nuclear weapons.[8] The potential everyday applications are vast; the element
americium is used in devices such as
smoke detectors and
spectrometers.[9][10]
^Silva, Robert J. (2006). "Fermium, Mendelevium, Nobelium and Lawrencium". In Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (Third ed.). Dordrecht, The Netherlands:
Springer Science+Business Media.
ISBN978-1-4020-3555-5.
Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: Traces of transuranium elements in terrestrial minerals? (
Online, PDF-Datei, 493 kB)
Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: The search for super heavy elements (SHE) in terrestrial minerals using XRF with high energy synchrotron radiation. (
Online, PDF-Datei, 446 kB)