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Synthetic element

From Wikipedia, the free encyclopedia
  Synthetic elements
  Rare radioactive natural elements; often produced artificially
  Common radioactive natural elements

A synthetic element is one of 24 known chemical elements that do not occur naturally on Earth: they have been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; thus, they are called "synthetic", "artificial", or "man-made". The synthetic elements are those with atomic numbers 95–118, as shown in purple on the accompanying periodic table:[1] these 24 elements were first created between 1944 and 2010. The mechanism for the creation of a synthetic element is to force additional protons into the nucleus of an element with an atomic number lower than 95. All known (see: Island of stability) synthetic elements are unstable, but they decay at widely varying rates; the half-lives of their longest-lived isotopes range from microseconds to millions of years.

Five more elements that were first created artificially are strictly speaking not synthetic because they were later found in nature in trace quantities: 43Tc, 61Pm, 85At, 93Np, and 94Pu, though are sometimes classified as synthetic alongside exclusively artificial elements.[2] The first, technetium, was created in 1937.[3] Plutonium (Pu, atomic number 94), first synthesized in 1940, is another such element. It is the element with the largest number of protons (atomic number) to occur in nature, but it does so in such tiny quantities that it is far more practical to synthesize it. Plutonium is known mainly for its use in atomic bombs and nuclear reactors.[4]

No elements with atomic numbers greater than 99 have any uses outside of scientific research, since they have extremely short half-lives, and thus have never been produced in large quantities.

Properties

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All elements with atomic number greater than 94 decay quickly enough into lighter elements such that any atoms of these that may have existed when the Earth formed (about 4.6 billion years ago) have long since decayed.[5][6] Synthetic elements now present on Earth are the product of atomic bombs or experiments that involve nuclear reactors or particle accelerators, via nuclear fusion or neutron absorption.[7]

Atomic mass for natural elements is based on weighted average abundance of natural isotopes in Earth's crust and atmosphere. For synthetic elements, there is no "natural isotope abundance". Therefore, for synthetic elements the total nucleon count (protons plus neutrons) of the most stable isotope, i.e., the isotope with the longest half-life—is listed in brackets as the atomic mass.

History

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Technetium

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The first element to be synthesized, rather than discovered in nature, was technetium in 1937.[8] This discovery filled a gap in the periodic table, and the fact that technetium has no stable isotopes explains its natural absence on Earth (and the gap).[9] With the longest-lived isotope of technetium, 97Tc, having a 4.21-million-year half-life,[10] no technetium remains from the formation of the Earth.[11][12] Only minute traces of technetium occur naturally in Earth's crust—as a product of spontaneous fission of 238U, or from neutron capture in molybdenum—but technetium is present naturally in red giant stars.[13][14][15][16]

Curium

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The first entirely synthetic element to be made was curium, synthesized in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso by bombarding plutonium with alpha particles.[17][18]

Eight others

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Synthesis of americium, berkelium, and californium followed soon. Einsteinium and fermium were discovered by a team of scientists led by Albert Ghiorso in 1952 while studying the composition of radioactive debris from the detonation of the first hydrogen bomb.[19] The isotopes synthesized were einsteinium-253, with a half-life of 20.5 days, and fermium-255, with a half-life of about 20 hours. The creation of mendelevium, nobelium, and lawrencium followed.

Rutherfordium and dubnium

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During the height of the Cold War, teams from the Soviet Union and the United States independently created rutherfordium and dubnium. The naming and credit for synthesis of these elements remained unresolved for many years, but eventually, shared credit was recognized by IUPAC/IUPAP in 1992. In 1997, IUPAC decided to give dubnium its current name honoring the city of Dubna where the Russian team worked since American-chosen names had already been used for many existing synthetic elements, while the name rutherfordium (chosen by the American team) was accepted for element 104.

The last thirteen

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Meanwhile, the American team had created seaborgium, and the next six elements had been created by a German team: bohrium, hassium, meitnerium, darmstadtium, roentgenium, and copernicium. Element 113, nihonium, was created by a Japanese team; the last five known elements, flerovium, moscovium, livermorium, tennessine, and oganesson, were created by Russian–American collaborations and complete the seventh row of the periodic table.

List of synthetic elements

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The following elements do not occur naturally on Earth. All are transuranium elements and have atomic numbers of 95 and higher.

Element name Chemical
Symbol		 Atomic
Number		 First definite
synthesis
Americium Am 95 1944
Curium Cm 96 1944
Berkelium Bk 97 1949
Californium Cf 98 1950
Einsteinium Es 99 1952
Fermium Fm 100 1952
Mendelevium Md 101 1955
Nobelium No 102 1965
Lawrencium Lr 103 1961
Rutherfordium Rf 104 1969 (USSR and US) *
Dubnium Db 105 1970 (USSR and US) *
Seaborgium Sg 106 1974
Bohrium Bh 107 1981
Hassium Hs 108 1984
Meitnerium Mt 109 1982
Darmstadtium Ds 110 1994
Roentgenium Rg 111 1994
Copernicium Cn 112 1996
Nihonium Nh 113 2003–04
Flerovium Fl 114 1999
Moscovium Mc 115 2003
Livermorium Lv 116 2000
Tennessine Ts 117 2009
Oganesson Og 118 2002
* Shared credit for discovery.

Other elements usually produced through synthesis

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All elements with atomic numbers 1 through 94 occur naturally at least in trace quantities, but the following elements are often produced through synthesis.

Element name Chemical
Symbol		 Atomic
Number		 First definite
discovery		 Discovery in nature
Technetium Tc 43 1937 1962
Promethium Pm 61 1945 1965[20]
Polonium Po 84 1898
Astatine At 85 1940 1943
Francium Fr 87 1939
Radium Ra 88 1898
Actinium Ac 89 1902
Protactinium Pa 91 1913
Neptunium Np 93 1940 1952
Plutonium Pu 94 1940 1941–42[21]

Technetium, promethium, astatine, neptunium, and plutonium were discovered through synthesis before being found in nature.

References

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  1. ^ Kulkarni, Mayuri (15 June 2009). "A Complete List of Man-made Synthetic Elements". ScienceStuck. Retrieved 15 May 2019.
  2. ^ See periodic table here for example.
  3. ^ "WebElements Periodic Table » Technetium » historical information". www.webelements.com. Webelements. Retrieved 7 November 2019.
  4. ^ Bradford, Alina (8 December 2016). "Facts About Plutonium". LiveScience. Retrieved 16 May 2019.
  5. ^ Redd, Nola (November 2016). "How Was Earth Formed?". Space.com. Retrieved 16 May 2019.
  6. ^ "Synthetic elements". Infoplease. Retrieved 16 May 2019.
  7. ^ Kulkarni, Mayuri (15 June 2009). "A Complete List of Man-made Synthetic Elements". ScienceStuck. Retrieved 16 May 2019.
  8. ^ Helmenstine, Anne Marie. "Technetium or Masurium Facts". ThoughtCo. Retrieved 15 May 2019.
  9. ^ "Technetium decay and its cardiac application". Khan Academy. Retrieved 15 May 2019.
  10. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  11. ^ Stewart, Doug. "Technetium Element Facts". Chemicool. Retrieved 15 May 2019.
  12. ^ Bentor, Yinon. "Periodic Table: Technetium". Chemical Elements. Retrieved 15 May 2019.
  13. ^ Hammond, C. R. (2004). "The Elements". Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9.
  14. ^ Moore, C. E. (1951). "Technetium in the Sun". Science. 114 (2951): 59–61. Bibcode:1951Sci...114...59M. doi:10.1126/science.114.2951.59. PMID 17782983.
  15. ^ Dixon, P.; Curtis, David B.; Musgrave, John; Roensch, Fred; Roach, Jeff; Rokop, Don (1997). "Analysis of Naturally Produced Technetium and Plutonium in Geologic Materials". Analytical Chemistry. 69 (9): 1692–9. doi:10.1021/ac961159q. PMID 21639292.
  16. ^ Curtis, D.; Fabryka-Martin, June; Dixon, Paul; Cramer, Jan (1999). "Nature's uncommon elements: plutonium and technetium". Geochimica et Cosmochimica Acta. 63 (2): 275. Bibcode:1999GeCoA..63..275C. doi:10.1016/S0016-7037(98)00282-8.
  17. ^ Krebs, Robert E. The history and use of our earth's chemical elements: a reference guide, Greenwood Publishing Group, 2006, ISBN 0-313-33438-2 p. 322
  18. ^ Hall, Nina (2000). The New Chemistry: A Showcase for Modern Chemistry and Its Applications. Cambridge University Press. pp. 8–9. ISBN 978-0-521-45224-3.
  19. ^ Ghiorso, Albert (2003). "Einsteinium and Fermium". Chemical & Engineering News Archive. 81 (36): 174–175. doi:10.1021/cen-v081n036.p174.
  20. ^ McGill, Ian. "Rare Earth Elements". Ullmann's Encyclopedia of Industrial Chemistry. Vol. 31. Weinheim: Wiley-VCH. p. 188. doi:10.1002/14356007.a22_607. ISBN 978-3527306732.
  21. ^ Seaborg, Glenn T.; Perlman, Morris L. (1948). "Search for Elements 94 and 93 in Nature. Presence of 94239 in Pitchblende1". Journal of the American Chemical Society. 70 (4). American Chemical Society (ACS): 1571–1573. doi:10.1021/ja01184a083. ISSN 0002-7863.
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