In chemistry, Transuranium elements (also known as transuranic elements) are the chemical elements with atomic numbers greater than 92, the atomic number of Uranium.
Of the elements with atomic numbers 1 to 92, all but four (43-technetium, 61-promethium, 85-astatine, and 87-francium) occur in nature.
All of the elements with higher atomic numbers, however, have had to be produced artificially. 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 vanished.
Those that can be found on earth now are artificially generated, via nuclear reactors or particle accelerators (Exception: Pu-239 is permanently generated in atomic quantities by neutrons from spontaneous fission in uranium ore with two subsequent beta decays (U-238 > U-239 > Np-239 > Pu-239)).
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.
The majority of the transuranium elements were produced by two groups:
- A group at the University of California, Berkeley, under three different leaders:
- Edwin Mattison McMillan, first to produce a transuranium element:
- Glenn T. Seaborg, next in order, who produced:
- 94. plutonium, Pu, named for the planet Pluto, following the same naming rule as it follows neptunium and Pluto follows Neptune in the planetary sequence.
- 95. americium, Am, named because it is an analog to europium, and so was named for the continent where it was first produced.
- 96. curium, Cm, named for Pierre and Marie Curie, famous scientists who separated out the first radioactive elements.
- 97. berkelium, Bk, named for the city of Berkeley, where the university is located.
- 98. californium, Cf, named for the state of California, where the university is located.
- Albert Ghiorso, who had been on Seaborg's team when they produced curium, berkelium, and californium, took over as director to produce:
- 99. einsteinium, Es, named for the great physicist Albert Einstein.
- 100. fermium, Fm, named for Enrico Fermi, the physicist who produced the first controlled chain reaction.
- 101. mendelevium, Md, named for the Russian chemist Dmitry Ivanovich Mendeleev, one of the two men who developed the periodic table of the chemical elements.
- 102. nobelium, No (see below).
- 103. lawrencium, Lr, named for Ernest O. Lawrence, a physicist best known for his development of the cyclotron, and the person for whom the Lawrence Laboratories (which hosted the creation of these transuranium elements) were named.
- 104. rutherfordium, Rf, named for Ernest Rutherford, who was responsible for the concept of the atomic nucleus.
- 105. An element for which the Berkeley group proposed the name hahnium, after Otto Hahn, the first chemist to detect evidence of nuclear fission, but which is now named dubnium, Db (see below).
- 106. seaborgium, Sg, named for Glenn T. Seaborg. This name caused controversy because Seaborg was still alive, but eventually became accepted by international chemists.
- A group at the Gesellschaft für Schwerionenforschung (Society for Heavy Ion Research) in Darmstadt, Hessen, Germany, under Peter Armbruster, who prepared:
- 107. bohrium, Bh, named for the Danish physicist Niels Bohr, important in the elucidation of the structure of the atom. The group had first suggested the name nielsbohrium, but the ultimately accepted name is bohrium.
- 108. hassium, Hs, named for the Latin form of the name of Hesse, the German Bundesland where this work was performed.
- 109. meitnerium, Mt, named for Lise Meitner, a German physicist who was one of the earliest scientists to become involved in the study of nuclear fission.
- 110. Darmstadtium, Ds named for Darmstadt, Germany. Where the Gesellschaft für Schwerionenforschung is situated which discovered the element.
- 111. This element has not yet been given a name.
- 112. This element has not yet been given a name.
Two other groups had worked on the preparation of transuranium elements, but their original reports have since been discredited:
- A group at the Nobel Institute in Sweden, which claimed to have produced element 102, and named it nobelium, in honor of Alfred Nobel, inventor of dynamite and donor of the endowment for the Nobel Prizes. The name "nobelium" was ultimately agreed upon, though their production is no longer accepted.
- A group at the Joint Institute for Nuclear Research in Dubna in Russia (then the Soviet Union) who claimed to have produced:
- 104, which they named kurchatovium after the Soviet chemist Ivan Kurchatov.
- 105. Although their claim is not accepted, the name dubnium is now official for this element, named for the city where they worked. They originally proposed nielsbohrium for this.
List of the transuranic elements:
93 Neptunium Np
94 Plutonium Pu
95 Americium Am
96 Curium Cm
97 Berkelium Bk
98 Californium Cf
99 Einsteinium Es
100 Fermium Fm
101 Mendelevium Md
102 Nobelium No
103 Lawrencium Lr
104 Rutherfordium Rf
105 Dubnium Db
107 Bohrium Bh
108 Hassium Hs
109 Meitnerium Mt
110 Darmstadtium Ds
111 Unununium Uuu
112 Ununbium Uub
113 Ununtrium Uut
114 Ununquadium Uuq
115 Ununpentium Uup
116 Ununhexium Uuh
117 Ununseptium Uus
118 Ununoctium Uuo
119 Ununennium Uue
120 Unbinilium Ubn