Physics:Synthetic element

From HandWiki
Short description: Chemical elements that do not occur naturally
  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 number 95–118, as shown in purple on the accompanying periodic table:[1] these 24 elements were first created between 1944 and 2010. Synthetic elements are made by forcing more protons into the nucleus of an element with an atomic number lower than 95. All synthetic elements are unstable, but they decay at widely varying rates: half-lives range from microseconds to millions of years.

Five more elements that were made artificially are strictly speaking not synthetic because they were later found in nature in trace quantities: 43Tc, 61Pm, 85At, 93Np, and 94Pu. However, they are sometimes called synthetic anyway.[2] The first, technetium (Tc), was created in 1937.[3] Plutonium (Pu, atomic number 94), first made 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 so have never been produced in large quantities.

Properties

All elements with atomic number greater than 94, decay fast enough into lighter elements that any atoms of these that may have existed when the Earth formed (~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

Technetium

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 it has no stable isotopes explains its natural absence on Earth (and the gap).[9] The longest-lived isotope of technetium, 97Tc, has a 4.21-million-year half-life,[10] so no technetium remains from the formation of the Earth.[11][12] Only minute traces of technetium occur naturally in Earth's crust—as a spontaneous fission product of 238U or by neutron capture in molybdenum—but technetium is present naturally in red giant stars.[13][14][15][16]

Curium

The first purely 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

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 made were einsteinium-253, with half-life 20.5 days; and fermium-255, with half-life about 20 hours. Mendelevium, nobelium, and lawrencium followed.

Rutherfordium and dubnium

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

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

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 1966
Lawrencium Lr 103 1961
Rutherfordium Rf 104 1966 (USSR), 1969 (US) *
Dubnium Db 105 1968 (USSR), 1970 (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 2003–4
Flerovium Fl 114 1999
Moscovium Mc 115 2003
Livermorium Lv 116 2000
Tennessine Ts 117 2010
Oganesson Og 118 2002
* Shared credit for discovery.

Other elements usually produced through synthesis

All elements with atomic numbers 1 through 94 occur naturally at least in trace quantities, but the following elements are often produced through synthesis. Technetium, promethium, astatine, neptunium, and plutonium were discovered through synthesis before being found in nature.

Element name Chemical
Symbol
Atomic
Number
First definite
discovery
Discovery in nature
Technetium Tc 43 1937 1962
Promethium Pm 61 1945 1965
Polonium Po 84 1898
Astatine At 85 1940 1943
Francium Fr 87 1939
Actinium Ac 89 1902
Protactinium Pa 91 1913
Neptunium Np 93 1940 1952
Plutonium Pu 94 1940 1941–2

References

  1. Kulkarni, Mayuri (15 June 2009). "A Complete List of Man-made Synthetic Elements". https://sciencestruck.com/synthetic-elements. 
  2. See periodic table here for example.
  3. "WebElements Periodic Table » Technetium » historical information". Webelements. https://www.webelements.com/technetium/history.html. 
  4. Bradford, Alina (8 December 2016). "Facts About Plutonium". https://www.livescience.com/39871-facts-about-plutonium.html. 
  5. Redd, Nola (November 2016). "How Was Earth Formed?". https://www.space.com/19175-how-was-earth-formed.html. 
  6. "Synthetic elements". https://www.infoplease.com/encyclopedia/science/chemistry/elements/synthetic-elements. 
  7. Kulkarni, Mayuri (15 June 2009). "A Complete List of Man-made Synthetic Elements". https://sciencestruck.com/synthetic-elements. 
  8. Helmenstine, Anne Marie. "Technetium or Masurium Facts". ThoughtCo. https://www.thoughtco.com/technetium-or-masurium-facts-606601. 
  9. "Technetium decay and its cardiac application". Khan Academy. https://www.khanacademy.org/test-prep/mcat/physical-sciences-practice/physical-sciences-practice-tut/e/cs-passage-4. 
  10. Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties". Chinese Physics C 41 (3): 030001. doi:10.1088/1674-1137/41/3/030001. Bibcode2017ChPhC..41c0001A. https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf. 
  11. Stewart, Doug. "Technetium Element Facts". https://www.chemicool.com/elements/technetium.html. 
  12. Yinon, Yinon. "Periodic Table: Technetium". http://www.chemicalelements.com/elements/tc.html. 
  13. Hammond, C. R. (2004). "The Elements". Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN 978-0-8493-0485-9. https://archive.org/details/crchandbookofche81lide. 
  14. Moore, C. E. (1951). "Technetium in the Sun". Science 114 (2951): 59–61. doi:10.1126/science.114.2951.59. PMID 17782983. Bibcode1951Sci...114...59M. 
  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. doi:10.1016/S0016-7037(98)00282-8. Bibcode1999GeCoA..63..275C. https://digital.library.unt.edu/ark:/67531/metadc704244/. 
  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. https://archive.org/details/newchemistry00hall. 
  19. Ghiorso, Albert (2003). "Einsteinium and Fermium". Chemical and Engineering News. 81 (36): 174–175. doi:10.1021/cen-v081n036.p174.

External links