Synthetic element

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.{{cite web |last1=Redd |first1=Nola |title=How Was Earth Formed? |url=https://www.space.com/19175-how-was-earth-formed.html |website=Space.com |date=November 2016 |access-date=16 May 2019}}{{cite web |title=Synthetic elements |url=https://www.infoplease.com/encyclopedia/science/chemistry/elements/synthetic-elements |website=Infoplease |access-date=16 May 2019}} 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.{{cite web |last1=Kulkarni |first1=Mayuri |title=A Complete List of Man-made Synthetic Elements |url=https://sciencestruck.com/synthetic-elements |website=ScienceStuck |date=15 June 2009 |access-date=16 May 2019}}

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.

The first element to be synthesized, rather than discovered in nature, was technetium in 1937.{{cite web |last1=Helmenstine |first1=Anne Marie |title=Technetium or Masurium Facts |url=https://www.thoughtco.com/technetium-or-masurium-facts-606601 |publisher=ThoughtCo |access-date=15 May 2019}} 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).{{cite web |title=Technetium decay and its cardiac application |url=https://www.khanacademy.org/test-prep/mcat/physical-sciences-practice/physical-sciences-practice-tut/e/cs-passage-4 |publisher=Khan Academy |access-date=15 May 2019}} With the longest-lived isotope of technetium, ⁹⁷Tc, having a 4.21-million-year half-life,{{NUBASE2020|ref}} no technetium remains from the formation of the Earth.{{cite web |last1=Stewart |first1=Doug |title=Technetium Element Facts |url=https://www.chemicool.com/elements/technetium.html |website=Chemicool |access-date=15 May 2019}}{{cite web |last1=Bentor |first1=Yinon |title=Periodic Table: Technetium |url=http://www.chemicalelements.com/elements/tc.html |website=Chemical Elements |access-date=15 May 2019}} 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.{{cite book |first = C. R. |last = Hammond |chapter = The Elements |title = Handbook of Chemistry and Physics |edition = 81st |publisher = CRC press |isbn = 978-0-8493-0485-9 |date = 2004 |url-access = registration |url = https://archive.org/details/crchandbookofche81lide }}{{cite journal|doi = 10.1126/science.114.2951.59|pmid = 17782983|date = 1951|last1 = Moore|first1 = C. E.|title = Technetium in the Sun|volume = 114|issue = 2951|pages = 59–61|journal = Science |bibcode=1951Sci...114...59M}}{{cite journal|doi = 10.1021/ac961159q|title = Analysis of Naturally Produced Technetium and Plutonium in Geologic Materials|date = 1997|last1 = Dixon|first1 = P.|journal = Analytical Chemistry|volume = 69|pages = 1692–9|last2 = Curtis|first2 = David B.|last3 = Musgrave|first3 = John|last4 = Roensch|first4 = Fred|last5 = Roach|first5 = Jeff|last6 = Rokop|first6 = Don|issue = 9|pmid = 21639292}}{{cite journal|doi =10.1016/S0016-7037(98)00282-8|title =Nature's uncommon elements: plutonium and technetium|first4 =Jan|last4 =Cramer|first3 =Paul|last3 =Dixon|first2 =June|date=1999|last2 =Fabryka-Martin|last1=Curtis|first1=D.|journal=Geochimica et Cosmochimica Acta|volume =63|pages =275|bibcode=1999GeCoA..63..275C|issue =2|url =https://digital.library.unt.edu/ark:/67531/metadc704244/}}

===Curium===

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.Krebs, Robert E. [https://books.google.com/books?id=yb9xTj72vNAC&pg=PA322 The history and use of our earth's chemical elements: a reference guide], Greenwood Publishing Group, 2006, {{ISBN|0-313-33438-2}} p. 322{{cite book|title = The New Chemistry: A Showcase for Modern Chemistry and Its Applications|first = Nina|last = Hall|publisher = Cambridge University Press|date = 2000|pages = [https://archive.org/details/newchemistry00hall/page/8 8]–9|isbn = 978-0-521-45224-3|url = https://archive.org/details/newchemistry00hall|url-access = registration}}

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.{{cite journal | doi=10.1021/cen-v081n036.p174 | title=Einsteinium and Fermium | year=2003 | last1=Ghiorso | first1=Albert | journal=Chemical & Engineering News Archive | volume=81 | issue=36 | pages=174–175 }} 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===

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.

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

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

‡ These five elements were discovered through synthesis before being found in nature.

{{Reflist}}

• {{cite web|url=http://www.britannica.com/EBchecked/topic/181416/einsteinium-Es|title=einsteinium (Es) - chemical element|website=Britannica.com|access-date=23 May 2017}}
• {{cite web|url=http://www.britannica.com/EBchecked/topic/374759/mendelevium-Md|title=mendelevium (Md) - chemical element|website=Britannica.com|access-date=23 May 2017}}
• {{cite web|url=http://encyclopedia2.thefreedictionary.com/synthetic+elements|title=synthetic elements|website=Encyclopedia2.thefreedictionary.com|access-date=23 May 2017}}
• {{cite web|url=http://education.jlab.org/itselemental/ele100.html|title=It's Elemental - The Element Fermium|website=Education.jlab.org|access-date=23 May 2017}}
• {{cite web |last1=Kulkarni |first1=Mayuri |title=A Complete List of Man-made Synthetic Elements |url=https://sciencestruck.com/synthetic-elements |website=ScienceStuck |date=15 June 2009 |access-date=15 May 2019}}

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Category:Nuclear physics

Category:Lists of chemical elements