Synthetic element - wikipedia Synthetic element This is the current revision of this page, as edited by Derek R Bullamore ( talk contribs ) at 16 : 16, 23 May 2017 ( Filled in 4 bare reference ( s ) with reFill ( ) ). The present address ( URL ) is a permanent link to this version. Revision as of 16 : 16, 23 May 2017 by Derek R Bullamore ( talk contribs ) ( Filled in 4 bare reference ( s ) with reFill ( ) ) ( diff ) ← Previous revision Latest revision ( diff ) Newer revision → ( diff ) This article has multiple issues. Please help improve it or discuss these issues on the talk page. ( Learn how and when to remove these template messages ) This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please help to improve this article by introducing more precise citations. ( May 2017 ) This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( August 2015 ) Synthetic elements Rare radioactive natural elements ; often produced artificially In chemistry, a synthetic element is a chemical element that does not occur naturally on Earth, and can only be created artificially. So far, 24 synthetic elements have been created ( those with atomic numbers 95 -- 118 ). All are unstable, decaying with half - lives ranging from 15.6 million years to a few hundred microseconds. Seven other elements were first created artificially and thus considered synthetic, but later discovered to exist naturally ( in trace quantities ) as well ; among them plutonium -- first synthesized in 1940 -- the one best known to laypeople, because of its use in atomic bombs and nuclear reactors. Contents 1 Properties 2 History 3 List of synthetic elements 3.1 Other elements usually produced through synthesis 4 References 5 External links Properties Synthetic elements are radioactive and decay rapidly into lighter elements -- possessing half - lives so short, relative to the age of Earth ( which formed approximately 4.6 billion years ago ), that any atoms of these elements that may have existed when the Earth formed have long since decayed. Atoms of synthetic elements only occur on Earth as the product of atomic bombs or experiments that involve nuclear reactors or particle accelerators, via nuclear fusion or neutron absorption. Atomic mass for natural elements is based on weighted average abundance of natural isotopes that occur in Earth 's crust and atmosphere. For synthetic elements, the isotope depends on the means of synthesis, so the concept of natural isotope abundance has no meaning. 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 The first element discovered through synthesis was technetium -- its discovery being definitely confirmed in 1936. This discovery filled a gap in the periodic table, and the fact that no stable isotopes of technetium exist explains its natural absence on Earth ( and the gap ). With the longest - lived isotope of technetium, Tc - 98, having a 4.2 - million - year half - life, no technetium remains from the formation of the Earth. Only minute traces of technetium occur naturally in the Earth 's crust -- as a spontaneous fission product of uranium - 238 or by neutron capture in molybdenum ores -- but technetium is present naturally in red giant stars. The first discovered synthetic element was curium, synthesized in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso by bombarding plutonium with alpha particles. The discoveries 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 radioactive debris from the detonation of the first hydrogen bomb. The isotopes discovered were einsteinium - 253, with a half - life of 20.5 days, and fermium - 255, with a half - life of about 20 hours. The discoveries of mendelevium, nobelium, lawrencium followed. During the height of the Cold War, the Soviet Union and United States independently discovered rutherfordium and dubnium. The naming and credit for discovery of those 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 made their discoveries 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. No element with an atomic number greater than 99 has any use outside of scientific research, as they have extremely short half - lives. 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 1971 Rutherfordium Rf 104 1966 ( USSR ), 1969 ( U.S. ) * Dubnium Db 105 1968 ( USSR ), 1970 ( U.S. ) * 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 2004 Flerovium Fl 114 2004 Moscovium Mc 115 2010 Livermorium Lv 116 2004 Tennessine Ts 117 2010 Oganesson Og 118 2006 * Shared credit for discovery. Other elements usually produced through synthesis All elements with atomic numbers 1 through 94 are naturally occurring at least in trace quantities, but the following elements are often produced through synthesis. Except for polonium, francium, actinium, and protactinium, they were all discovered through synthesis before being found in nature. Element name Chemical Symbol Atomic Number First definite discovery Technetium Tc 43 1936 Promethium Pm 61 1945 Polonium Po 84 1898 Astatine At 85 1940 Francium Fr 87 1939 Actinium Ac 89 1902 Protactinium Pa 91 1913 Neptunium Np 93 1940 Plutonium Pu 94 1940 References External links `` einsteinium ( Es ) - chemical element ''. Britannica.com. Retrieved 23 May 2017. `` mendelevium ( Md ) - chemical element ''. Britannica.com. Retrieved 23 May 2017. `` synthetic elements ''. Encyclopedia2.thefreedictionary.com. Retrieved 23 May 2017. `` It 's Elemental - The Element Fermium ''. Education.jlab.org. Retrieved 23 May 2017. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Synthetic_element&oldid=781851963 '' Categories : Nuclear physics Synthetic elements Lists of chemical elements Hidden categories : Articles lacking in - text citations from May 2017 All articles lacking in - text citations Articles needing additional references from August 2015 All articles needing additional references Talk Article Talk More Contents About Wikipedia العربية Български Català Dansk Español Euskara فارسی Français Gaeilge Galego 한국어 हिन्दी Bahasa Indonesia ಕನ್ನಡ Kiswahili Lumbaart Magyar Bahasa Melayu 日本 語 Português Română Русский Svenska தமிழ் ไทย 中文 Edit links This page was last edited on 23 May 2017, at 16 : 16. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: how many artificial elements are in the periodic table
Answer: 24