Periodic Table of Elements: Los Alamos National Laboratory 7, 6, 5, 4, 3, 0 History Plutonium is the second transuranium element of the actinide series. Element 93 was discovered in 1940/41 by Glenn T. Seaborg , Edwin M. McMillan , J. W. Kennedy , and A. C. Wahl by deuteron bombardment of uranium-238 in the 60-inch cyclotron at the University of California, Berkeley Lab. They first synthesized neptunium-238 (half-life 2.1 days) which subsequently beta-decayed to form a new heavier element with atomic number 94 and atomic weight 238 (half-life 87.7 years). It was fitting that element 94 be named after the next planetoid, Pluto following the precedence that uranium was named after the planet Uranus and neptunium after the planet Neptune.

Seaborg submitted a paper to the journal Physical Review in March 1941 documenting the discovery, but the paper was quickly withdrawn when it was found that an isotope of plutonium, Pu-239 could undergo nuclear fission making it useful in developing an atomic bomb. Pu-239 had a fission cross-section 50% greater than that of 235U, the best fissioning element known at that time. Seaborg was called away from Berkeley to lead the Plutonium Production Lab or "Met Lab" at the University of Chicago. The Met Lab was to produce useful quantities of plutonium as part of the secret Manhattan Project during World War II to develop an atomic bomb. On August 18, 1942, a trace quantity of plutonium was isolated and measured at the Met Lab for the first time. About 50 micrograms of Pu-239 combined with uranium and fission products was produced and only about 1 microgram was isolated. This was enough material for chemists to determine the new element's atomic weight. In November 1943 a few milligrams of PuF3 was reduced to create the first sample of plutonium metal.

Enough plutonium was produced to make it the first man-made element to be visible to the unaided eye. The nuclear properties of plutonium-239 were also being studied and researchers found that when hit with a neutron it fissions by releasing energy and more neutrons. These neutrons can hit neighboring atoms of Pu-239 and so on, in an exponentially fast chain-reaction, releasing a tremendous amount of energy. This energy could result in an explosion large enough to destroy a city or fuel a nuclear reactor. During WW II the three primary research and production sites of the Manhattan Project were the Plutonium Production Facility at what is now the Hanford Site , Washington, the Uranium Enrichment facilities at Oak Ridge, Tennessee , and the weapons research and design laboratory, now known as Los Alamos National Laboratory . In 1943, the first production reactor that made Pu-239 was the X-10 Graphite Reactor built at a facility in Oak Ridge, Tennessee that later became the Oak Ridge National Laboratory. The Manhattan Project produced the plutonium for the "Trinity Test" conducted in New Mexico by Los Alamos Laboratory Director Robert Oppenheimer and Army General Leslie Groves.

The world’s first atomic bomb ("The Gadget") was exploded near Socorro, New Mexico on July 16, 1945, resulting in an explosion with an energy equivalent of approximately 20,000 tons of TNT . The first atomic bomb used in war had a uranium core and was dropped on Hiroshima, Japan on August 6, 1945. The second atomic bomb used had a plutonium core and was nicknamed " Fat Man " because of its round shape. It was used to destroy Nagasaki, Japan in August 9, 1945, which put an end to WW II. Publication of the discovery and the naming of the new element plutonium was delayed until a year after the end of World War II . Seaborg originally considered the name "plutium", but later thought that it did not sound as good as "plutonium." Later, during the Cold-War era, large stockpiles of weapons-grade plutonium were built up by both the Soviet Union and the United States. Each year about 20 tons of plutonium is still produced as a by-product of the nuclear power industry.

As of 2007 it was estimated that the plutonium stockpile was about 500 tons, world-wide. Since the end of the Cold War these stockpiles have become a focus of nuclear proliferation concerns. In 2000, the United States and the Russian Federation mutually agreed to each dispose of 34 tons of weapon grade plutonium before the end of 2019 by converting it to a mixed uranium-plutonium oxide (MOX) fuel to be used in commercial nuclear power reactors. Today plutonium-239 remains an important component of nuclear weapons, and the United States maintains plutonium-related capabilities in support of national defense and global nuclear deterrence. Pu-239 for civilian nuclear power plants provides energy for many nations. Plutonium-238 continues to be vital to space exploration pushing the limits beyond which manned space exploration is possible and satisfying our quest for knowledge. Isotopes Twenty-three radioactive isotopes of plutonium have been characterized from mass numbers 228 to 247. Nine of these exhibit metastable states , though these all have half-lives less than one second.

The longest-lived isotopes are plutonium-244, with a half-life of 80.8 million years, plutonium-242, with a half-life of 373,300 years, and plutonium-239, with a half-life of 24,110 years. All of the remaining radioactive isotopes have half-lives less than 7,000 years. The primary decay modes of isotopes with mass numbers lower than plutonium-244, are spontaneous fission and α emission , mostly forming uranium and neptunium isotopes as decay products along with a variety of daughter fission products. The primary decay mode for isotopes with mass numbers higher than plutonium-244 is by β emission , mostly forming americium isotopes as daughter decay products. Plutonium-241 is the parent isotope of the neptunium decay series , decaying to americium-241 via β decay.

By far of greatest importance is the isotope 239Pu produced in extensive quantities in nuclear reactors from natural uranium: 238U (n, gamma) → 239U (beta) → 239Np (beta) → 239Pu Plutonium-238 with a half-life of 87.7 years is another important isotope. Both Pu-239 and Pu-238 have many practical applications as discussed below. Properties Plutonium is unique among the elements in its physicochemical complexities by virtue of its position at a transitional location in the periodic table where the 5f electrons are at the border between delocalized (not associated with a single atom) and localized (associated with a single atom) behavior and it is considered one of the most complex of the elements. Plutonium also sits near the juncture where the actinide series transitions from main d-block element chemistry to rare earth like behavior as a result of the actinide contraction. Because of its defense and commercial importance, plutonium is one of the most intensely investigated of elements.

Plutonium metal has a bright silvery appearance at first and takes on a dull gray, yellow or olive green tarnish when oxidized in air. A relatively large piece of plutonium is warm to the touch because of the energy given off by alpha decay. Larger pieces will produce enough heat to boil water. The metal readily dissolves in concentrated mineral acids. Plutonium metal normally has six allotropes or crystal structures; alpha (α), beta (β), gamma (γ), delta (δ), delta prime (δ') and epsilon (ε). It forms a seventh phase (zeta, ζ) under high temperature and a limited pressure range. These allotropes have very similar energy levels but significantly varying densities (from 16.00 to 19.86 grams/cm3) and crystal structures . This makes plutonium very sensitive to changes in temperature, pressure, or chemistry, and allows for dramatic volume changes following phase transitions . At room temperature plutonium is in its alpha (α) form , the most common structural form of the element. It is as hard and brittle as cast iron unless alloyed with other metals to form the room-temperature stabilized delta (δ) phase which makes it soft and ductile.

Unlike most metals, it is not a good conductor of heat or electricity . It has a low melting point (640 °C) and an unusually high boiling point (3,228 °C). A ring of 99.96% pure electro-refined plutonium (Los Alamos National Laboratory) Plutonium can form alloys and intermediate compounds with most other metals. Gallium, aluminum, americium, scandium and cerium can stabilize the δ phase of plutonium metal. Nuclear fuel pellets can be formed by alloying plutonium with various metals such as: aluminum; zirconium; cerium; cerium-cobalt; uranium-titanium, uranium-zirconium and uranium-molybdenum. Thorium-plutonium-uranium alloys were investigated as a nuclear fuel for fast breeder reactors. A plutonium-gallium-cobalt alloy (PuCoGa5) was found to be an unconventional superconductor, showing superconductivity below 18.5 Kelvin, an order of magnitude higher than the highest between heavy fermion systems known. Plutonium forms compounds with a variety of other elements. Plutonium reacts with pure hydrogen, forming plutonium hydride s.

It also reacts readily with oxygen, forming PuO and PuO2 as well as intermediate and sub-stoichiometric oxides. The metal reacts with the halogens , giving rise to trivalent Pu compounds with the general formula PuX3 where X can be F , Cl , Br or I and tetravalent plutonium compounds such as PuF4 . The following oxyhalides are observed: PuOCl, PuOBr and PuOI. Plutonium reacts with carbon to form PuC, nitrogen to form PuN and silicon to form PuSi2. Pu3+ and Pu4+ oxalates are important intermediates that are calcined to form oxides as a step in plutonium processing. Other important compounds in reprocessing are fluoride, peroxide, acetylacetone, carbonate and hydroxide. The color displayed by plutonium solutions depends on both the oxidation state and the extent of complexation by various ligands.

In aqueous solution plutonium exhibits five ionic valence states: Pu+3 (blue lavender), Pu+4 (salmon-colored, when uncomplexed), PuO+ (lavender), PuO+2 (orange-brown) and PuOxOHy (dark green in basic solution). The pentavalent ion, PuO+ is unstable in aqueous solutions and it disproportionates into Pu+4 and PuO+2. However, PuO2+ can be stabilized in aqueous solution in a narrow pH range around 4.5. By virtue of the close proximity of the electrode potentials of the various plutonium redox couples (~ 1 Volt/NHE), four oxidation states can co-exist in solution simultaneously: Pu3+, Pu4+, PuO2+ and PuO22+. Various oxidation states of plutonium in aqueous solution; all in non-complexing perchloric acid, except Pu(VII) in strong base. (D. E. Hobart and P.D. Palmer, Los Alamos National Lab.) Pu4+ is a "hard" (ionic) cation with the largest electronic charge of plutonium ions and it forms complexes with a variety of inorganic and organic ligands.

In dilute perchloric acid, Pu4+ is un-complexed and is salmon-colored. However in concentrated acids, Pu4+ forms anionic complexes such as: Pu(NO3)62- (dark green) and Pu(Cl)62- (brick red). Pu4+, having a high ionic charge readily hydrolyzes (combines with hydroxide ion) at near-neutral pH values forming a green colloidal suspension that behaves like a solution but is actually a solid precipitate that can be separated by ultra-centrifugation. Plutonium-organic complexes are very important for separation, reprocessing, and purification and include: Tributyl phosphate (TBP); Di-(2-ethylhexyl)phosphoric acid (DEHPA or HDEHP); octyl(phenyl)-N,N-diisobutyl-carbamoylmethylphosphine oxide (CMPO); crown-ethers; and many others. Production Plutonium is the heaviest primordial element in existence by virtue of its most stable isotope, plutonium-244, whose half-life of about 80 million years is just long enough for the element to be found in trace quantities in nature.

In 1971 mass spectrometric measurements of plutonium isolated from Precambrian bastnasite (a lanthanide chloride-fluoride mineral) by Hoffman and coworkers confirmed the presence of Pu-244 in nature. Although the existence of Pu-244 as an extinct radioactive element had been postulated to explain the xenon isotope ratios observed in meteorites, this is the first indication of its present existence in nature. Plutonium also exists in trace quantities in naturally occurring uranium ores. It is formed in much the same manner as neptunium: by irradiation of natural uranium with the neutrons followed by beta decay. Exceedingly small amounts of Pu-238, attributed to the extremely rare double-beta decay of U-238, have been found in natural uranium samples. Plutonium was most likely formed by neutron activation of natural U-238 at the Oklo natural reactor but if formed it has long since decayed away. Plutonium is for the most part a by-product of nuclear reactions in reactors where some of the neutrons released by the fission process convert U-238 nuclei into plutonium.

Plutonium-238 and -239 are the most widely synthesized isotopes. Plutonium-239 is synthesized via the following reaction using uranium (U) and neutrons (n) via beta decay (β−) with neptunium as an intermediate: Plutonium-238 is synthesized by bombarding uranium-238 with deuterons in the following first discovery reaction: Uses Plutonium has assumed the position of dominant importance among the transuranium elements because of its use as an explosive ingredient in nuclear weapons and the place which it holds as a key material in the development of industrial use of nuclear power. During fission, a fraction of the binding energy, which holds a nucleus together, is released as a large amount of electromagnetic and kinetic energy which is quickly converted to thermal energy. Fission of a kilogram of plutonium-239 can produce an explosion equivalent to 21,000 tons of TNT which is equivalent to about 22 million kilowatt hours of heat energy. In 1982 it was estimated that about 300,000 kg had accumulated.

The most common chemical process, PUREX (Plutonium–URanium EXtraction) reprocesses spent nuclear fuel to extract plutonium and uranium which can be used to form a mixed U/Pu oxide or "MOX" fuel for reuse in nuclear power reactors. MOX fuel production is also a good mechanism to reduce excessive defense plutonium stockpiles for peaceful purposes, which in effect is forging "swords into plowshares." Plutonium isotopes undergo radioactive decay, which produces decay heat . Different isotopes produce different amounts of heat per mass. Pu-238 with a half-life of 88 years has a relatively high heat production rate which makes it useful as a power source with a long service life. The decay heat is usually listed as watt/kilogram, or milliwatt/gram. Pu-238 is a heat source in radioisotope thermoelectric generators, which are used to power spacecraft and extra-terrestrial rovers. As a power and heat source, Pu-238 has also been used to power instruments left on the Moon by Apollo astronauts, weather satellites and interplanetary probes and powers the Cassini Saturn mission and the Mars rovers.

Plutonium-238 was at one time used successfully to power artificial heart pacemakers but has been replaced by lithium-based primary cells. Plutonium-238 was studied as a way to provide supplemental heat to scuba divers. Pu-238 mixed with beryllium is a convenient method to generate neutrons. Pu-238 powers the Cassini Mission now orbiting Saturn. (NASA) Hazards Plutonium, along with all of the other transuranium elements, is a radiological hazard and must be handled with specialized equipment and precautions. Animal studies have found that a few milligrams of plutonium per kilogram of tissue are lethal. Plutonium is more dangerous when inhaled than when ingested. When inhaled, plutonium can pass into the bloodstream moving throughout the body and into the bones, liver, or other body organs. Plutonium that reaches body organs generally stays in the body for decades and continues to expose the surrounding tissue to radiation and thus may cause cancer. Precautions must also be taken to prevent the unintentional formulation of a critical mass.

Pure Pu-239 metal present in sufficient quantity with an appropriate geometry can form a critical mass and pose a serious and often lethal criticality event. Low levels of plutonium in the environment is a result of world-wide fallout from numerous above-ground nuclear tests during the Cold War (now banned) pose little health hazard. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern. Further Reading D. L. Clark, S. S. Hecker, G. D. Jarvinen, and M. P. Neu (2006) "Plutonium", Chapter 7 in The Chemistry of the Actinide and Transactinide Elements, Third Edition, L. R. Morss, J. Fuger, and N. M. Edelstein, Eds, Springer Publishers. Los Alamos Science (2000) Number 26, Volume I and II, Los Alamos National Laboratory report LA-UR-00-4100. Updated by Dr. David Hobart, August 2013.

LA-UR-13-26653 The Search for "Heavy" Elements Appendix The Search for "Heavy" Elements When a nucleus captures a neutron, it often tries to correct for its neutron excess by beta decay, turning a neutron into a proton and thus creating an atom with atomic number Z increased by one unit. This commonly observed phenomenon suggests a way to create new elements of increased atomic number and thus to create ever more massive elements that are not found on Earth. Most of these elements are radioactive, with very short half-lives. However, theories of nuclear structure predict that at a certain atomic number, which is currently beyond present experimental limits, new long-lived nuclei can be created. The most massive naturally occurring element on Earth is uranium (U), with a nucleus of 92 protons. In 1934, scientists started the search for more massive elements with 93 or more protons. They succeeded in 1940 when neptunium (Np, Z = 93) was synthesized at the University of California, Berkeley. Edwin McMillan and Philip Abelson observed Np while studying fission products produced in the bombardment of 238U with thermal neutrons.

They found a radioactive reaction product that was not a fission product. This product was formed by the capture of a neutron to produce 239U, which subsequently b- decayed to 239Np via the reaction 239U + 1n Æ 239U (23.5 min) Æ 239Np (2.36 d), where the half life of the nucleus is indicated in the parenthesis. McMillan and Abelson chemically separated this new element, Np, from the interfering fission products and chemically identified it as neptunium. Since this breakthrough discovery, scientists from all over the world have been trying to discover ever more massive artificially produced elements. Plutonium (Pu, Z = 94) was discovered in 1941 by bombarding a uranium target with deuterons (a hydrogen nucleus with one proton and one neutron) in the 60-Inch Cyclotron at Berkeley.

Glenn Seaborg , Arthur Wahl and Joseph Kennedy chemically separated neptunium from the target and detected alpha particles from the plutonium daughter nuclei, as: 238U + 2H Æ 2 1n + 238Np (2.1 d) Æ 238Pu (88 yr) . They chemically identified the isotope 238Pu. Then, joined by Emilio Segre, they identified 239Pu and showed that it was fissionable with thermal neutrons. Once 239Pu was discovered, there was the potential for using it as a new target to produce more massive elements. In 1944 a 239Pu target was bombarded with alpha particles at the 60-Inch Cyclotron to produce curium (Cm, Z = 96) through the following nuclear reaction 239Pu (24,110 yr) + 4He Æ 242Cm (162.8 d) + 1n.

After bombardment the material was sent to the Metallurgical Laboratory at The University of Chicago for chemical separation and identification of the new element. 242Cm decays to 238Pu by emitting alpha particles. The identification of curium was possible because the alpha decay of the daughter nucleus, 238Pu, was already known and could be used as a signature for the identification of the curium precursor. The discovery of americium (Am, Z = 95) soon followed when a 239Pu target was bombarded with thermal neutrons in a nuclear reactor. Plutonium captured several neutrons and ultimately became americium (241Am): 239Pu (24,110 yr) + 1n Æ 240Pu (6,564 yr) + 1n Æ241Pu (14.4 yr), and 241Pu (14.4 yr) Æ 241Am (432.7 yr) + 1n Æ 242Am (16.0 h) Æ 242Cm (162.8 d).

Americium was chemically separated from plutonium and further identified by observing its beta decay to the known 242Cm isotope. Once americium and curium were discovered and isolated in macroscopic amounts, they were used as targets to produce more massive elements through particle bombardments. Berkelium (Bk, Z = 97) was produced by bombarding milligram quantities of americium with helium ions, 241Am (432.7 yr) + 4He Æ 243Bk (4.5 h) + 2 1n. Rapid chemical techniques were developed in order to separate and identify this new short-lived element. Likewise, californium (Cf, Z = 98) was produced in a helium bombardment of a target made of microgram amounts of curium by 242Cm (162.8 d) + 4He Æ 245Cf (45 min) + 1n. The identification of this element was accomplished with only the 5000 atoms produced in this experiment.

The next two elements, einsteinium (Es, Z = 99) and fermium (Fm, Z = 100), were unexpectedly found in the debris from the "Mike" thermonuclear explosion that took place in the Pacific Ocean in 1952. Debris from the explosion was collected and analyzed at several laboratories, and the new elements were discovered in chemical separations of the material. Scientists explained the production of einsteinium and fermium through multiple neutron captures by the uranium used in the thermonuclear device followed by several successive beta decays, which ultimately resulted in atoms with atomic numbers 99 and 100. The last three elements in the actinide series are mendelevium (Md, Z = 101), nobelium (No, Z = 102) and lawrencium (Lr, Z = 103). Mendelevium was truly a unique discovery because the new element was produced and identified virtually one atom at a time.

Einsteinium was bombarded with helium ions to produce mendelevium through: 253Es (20.5 d) + 4He Æ 256Md (78.1 min) + 1n. The production of mendelevium was estimated to be only a few atoms per experiment. The reaction products from the bombardment were collected on thin gold foils that were dissolved in an acid solution, and then chemically treated in order to separate and identify the Md atoms. This is commonly called the recoil method, and is used when small amounts of atoms are produced. The discovery of nobelium was controversial. A team of scientists from several different laboratories claimed discovery in 1957. However, scientists from the United States and the Soviet Union could not confirm their findings. The original claim was proven to be false; the product that was thought to be nobelium was actually something completely different. Nobelium was finally produced and positively identified in 1958 through the following reaction: 246Cm (4730 yr) + 12C Æ 254No (55 s) + 4 1n.

The first identification of lawrencium was made at the Berkeley Labs Heavy Ion Linear Accelerator (HILAC) in 1961. Several targets of californium isotopes were bombarded with beams of boron. The reaction products were collected on a mylar tape and moved past a series of alpha detectors. The element lawrencium was identified on the basis of the known alpha decays of its descendant nuclei. Once the actinide series was filled in the periodic table, work was started to produce the transactinide elements. The most recent version of the periodic table includes transactinide elements from rutherfordium (Rf, Z = 104) to element 112, which has not yet been named. As scientists tried to discover and identify the transactinide elements, they encountered several problems that made their task extremely difficult. The rates for producing these elements in accelerator bombardments were incredibly low. Consequently, only a few atoms could be produced over the course of the entire experiment. Sometimes these experiments went on continuously for several weeks. In addition, the half-lives of the transactinides are very short, making their identification a difficult challenge.

Unlike neptunium and plutonium, these elements may undergo radioactive decay before being detected. As a result, chemical separations are generally very difficult to perform for identifying transactinides. In order to confirm that a new element has actually been made, members of its decay chain must be detected and traced back as a signature to the unknown element. Elements 104 through 112 were discovered by observing the decay chain of their descendant nuclei. Only a few atoms of these new elements were produced in each experiment. The atoms were isolated from the target and beam material by using a particle separator which separates atoms based on their different masses. The atoms were then allowed to decay and the subsequent alpha particle decay products from the descendant nuclei were correlated to identify the unknown parent nucleus. In the discovery of element 112, the individual atoms were identified by the decay chains of parent-daughter-granddaughter nuclei (above). Different combinations of target and projectile were used in accelerators to produce these new elements. Rutherfordium (104), dubnium (105), and seaborgium (106) were synthesized and identified at Berkeley.

Bohrium (107), hassium (108), and meitnerium (109) were synthesized and identified in the early 1980s at the Gesellschaft für Schwerionenforschung (GSI) laboratory near Darmstadt, Germany. In the 1990s, unnamed element 110 was identified at the GSI, Berkeley, and Dubna laboratories, and elements 111 and 112 were found at the GSI laboratory. The names for these new elements are under discussion. New experimental techniques and apparatus are being developed for scientists to extend the periodic table to even more massive elements. A more efficient particle separator, will use magnetic fields to separate atoms based on their mass and charge. This equipment will allow detection of nuclides with low production rates and extremely short half-lives. There are plans for using such a separator to produce elements 114 and 116. The present limits for discovering new elements are based on the low production rates and short half-lives. The hope is that new development in detection equipment will increase the sensitivity for detecting fewer atoms (or even a single atom) with very short half-lives.

A widely used theory predicts the existence of elements up to Z = 125. In this model, more massive elements would be so unstable that their nuclei would immediately fly apart into nucleons and nuclear fragments and never become atoms. Traditionally, the discoverers of a new element chose its name. Then the International Union of Pure and Applied Chemistry (IUPAC) officially approves the proposed name. However, for several of the transfermium elements (Z = 102 and higher) there had been competing claims to their discovery. Recently, the names for elements have been decided up to Z = 109. Table 8-1 lists the currently approved IUPAC names. It has been possible to study the chemical properties on the macroscopic scale for elements as massive as einsteinium (element 99) and on the tracer scale for elements as massive as seaborgium (element 106). The elements beyond the actinides in the Periodic Table are termed the "transactinides" and are shown in a Modern Periodic Table as in Fig. 8-2 with all of the undiscovered elements through number 118 in their expected places. Table 8-1.

"Heavy" element names that are approved by IUPAC. Element Number plutonium facts, information, pictures | Encyclopedia.com articles about plutonium Note: This article, originally published in 1998, was updated in 2006 for the eBook edition. Overview Plutonium is a synthetic (artificial) element. It exists naturally only in the smallest imaginable amounts. Plutonium was first prepared artificially by a team of researchers at the University of California at Berkeley (UCB) in 1941. News of this discovery was not released, however, until 1946. This delay was caused by the need for secrecy about scientific developments during World War II (1939-45). Plutonium is a member of the actinide family. The actinides occur in Row 7 of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. The actinides get their name from element 89, actinium, which is sometimes considered the first member of the family. Plutonium is also called a transuranium element.

The term transuranium means "beyond uranium." Elements with atomic numbers greater than that of uranium (92) are called transuranium elements. SYMBOL PRONUNCIATION plu-TOE-nee-um Plutonium has two important uses. First, some of its isotopes will undergo nuclear fission. Nuclear fission is a process in which an element is bombarded with neutrons. The element breaks apart into simpler elements, releasing large amounts of energy. Plutonium has been used to make nuclear weapons (such as "atomic bombs") and in nuclear power plants to produce electricity. Plutonium has also been used as a portable energy supply in space probes and other space vehicles. Discovery and naming In 1940, American physicists Edwin McMillan (1907-91) and Philip Abelson (1913- ) discovered the first transuranium element, neptunium (atomic number 93). The neptunium they produced was radioactive. They predicted it would break down to form a new element, atomic number 94. But McMillan and Abelson were called away to do research on the atomic bomb.

They suggested to a colleague, Glenn Seaborg (1912- ), that he continue their research on neptunium. Seaborg and his associates picked up where McMillan and Abelson had left off. They eventually proved that element 94 did exist. The proof came in an experiment they conducted in a particle accelerator at UCB. A particle accelerator is sometimes called an "atom smasher." It is used to cause small particles, such as protons, to move at very high speeds. The particles then collide with targets, such as gold, copper, or tin. When struck by the particles, the targets break apart, forming new elements and other particles. Seaborg's team suggested the name plutonium for the new element, in honor of the planet Pluto. The two elements just before plutonium in the periodic table had also been named for planets: uranium for Uranus and neptunium for Neptune. Glenn Seaborg later went on to find a number of other elements. One of those elements, atomic number 106, has been named seaborgium in his honor.

(See transfermium elements in this volume.) Physical properties Plutonium is a silvery-white metal with a melting point of 639.5°C (1,183°F) and a density of 19.816 grams per cubic centimeter. Chemical properties Plutonium is highly reactive and forms a number of different compounds. Occurrence in nature Scientists now know that very small amounts of plutonium occur in the Earth 's crust. It is formed in ores of uranium. When uranium breaks down, it sometimes forms plutonium in very small quantities. Scientists believe that the abundance of plutonium in the earth is about one quintillionth parts per million. Isotopes About 15 isotopes of plutonium are known to exist. All of these isotopes are radioactive. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary.

Each variation is an isotope. Plutonium is named after the planet Pluto. The most stable isotopes of plutonium are plutonium-242 and plutonium-244. The half lives of these two isotopes are 376,300 years and 82,600,000 years respectively. The half life of a radioactive element is the time it takes for half of a sample of the element to break down. Consider the isotope plutonium-242, with its half life of 376,300 years. In 376,300 years (one half life), only half of a sample prepared today would still be plutonium-242. The rest would have broken down into a new isotope. Extraction Plutonium is extracted from natural sources only rarely and only for the purposes of research. Uses The most important uses of plutonium depend on two of its properties. First, the radiation given off by plutonium occurs as heat. In fact, plutonium gives off so much heat that the metal feels warm when it is touched.

If a large piece of plutonium is placed into water, the heat released can cause the water to boil. Plutonium provides electrical power on space probes and space vehicles. This property makes plutonium a good choice for certain thermoelectric generator applications. A thermoelectric generator is a device that converts heat into electricity. Plutonium generators are not practical on a large scale basis. But they are very desirable for special conditions. For example, they have been used to provide electrical power on space probes and space vehicles. They have also been used in artificial pacemakers for people with heart conditions. The isotope most commonly used for this application is plutonium-238 because the radiation it gives off does not pose a threat to people's health. Plutonium is also used as a fuel in nuclear power plants and in making nuclear weapons ("atomic bombs"). The isotope used for this purpose is plutonium-239. It is used because it will undergo nuclear fission. Very few isotopes will undergo nuclear fission. Two isotopes of uranium, uranium-233 and uranium-235, are among these.

But uranium-233 does not occur at all in nature and uranium-235 occurs in only very small amounts. Using fuel to make fuel T he production of plutonium fuel (plutonium-239) is a fascinating story. When nuclear reactors were first built, they all used uranium-235 as a fuel. Of the three naturally occurring isotopes of uranium, only uranium-235 will undergo fission. But the uranium used in a nuclear reactor is never pure uranium. Instead, it is natural uranium with an increased amount of uranium-235. The uranium is said to be "enriched" with uranium-235. But a lot of the main isotope of uranium, uranium-238, remains mixed with the uranium-235. Fission of uranium-235 occurs when neutrons are fired into the reactor. Neutrons are subatomic particles with no electric charge. They cause uranium-235 to break apart, giving off energy. That energy is then used to make electricity. But neutrons also collide with uranium-238 isotopes in the reactor. This isotope does not undergo fission, but does undergo another kind of change.

It soaks up neutrons and changes into plutonium-239: The plutonium that is formed can be removed from the reactor. It is then purified and re-used as fuel in another nuclear reactor. What an amazing process this is! One could compare it to the burning of coal to make electricity. In a coal-fired power plant, coal is burned to boil water. Steam runs turbines that make electricity, but when the coal burns up, it's gone. In a nuclear reactor, the breakdown of uranium-235 atoms gives off energy like the burning of coal. Over time, most of the uranium-235 atoms are used up. But while this is happening, a new fuel is being made! Atoms of plutonium-239 are being produced from atoms of uranium-238. Some reactors are operated primarily to make plutonium, not to make electricity. These reactors are called breeder reactors because they generate new fuel as they operate. By contrast, plutonium-239 can be made fairly easily in nuclear power reactors. It is a by-product, or "waste product," of these reactors. It can be removed from the reactor, purified, and then re-used to make electrical power.

Compounds No plutonium compounds have any commercial application. Plutonium is one of the most toxic elements known. Scientists do not handle it directly. They use remote control devices and stand behind special shielding to protect themselves from the radiation produced by plutonium. Health effects Plutonium is one of the most toxic elements known. In the body, it tends to concentrate in bones. One of its most serious health effects on a long-term basis is bone cancer. Scientists who work with plutonium do not handle the metal directly. Instead, they use remote control devices. They always stand behind special shielding to protect themselves from the radiation produced by plutonium. Cite this article Pick a style below, and copy the text for your bibliography. MLA density: 19.84g/cm 3 most common ions: Pu 3+, Pu 4+, PuO 2+, PuO 22+, PuO 53− Plutonium was discovered by Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl in 1940. They prepared a new isotope of neptunium, 238Np, which decayed by β -emission to 238Pu.

Their work as part of the Manhattan Project was kept secret and was finally reported in 1946, after World War II , although the existence of plutonium had been revealed to the world earlier, when the atomic bomb was dropped over Nagasaki , Japan . There are sixteen isotopes of plutonium, having mass numbers ranging from 232 to 247. The principal isotopes of Pu are those having mass numbers 238, 239, 240, 241, 242, and 244. Ton quantities of 239Pu (having a half-life of 2.4 × 04 y) are available. The isotope 239Pu is the source material for nuclear weapons and is produced via neutron capture reactions on 238U in nuclear reactors. About 110 tons of 239Pu are generated in nuclear power plants each year, with approximately 40 percent of the energy produced in the nuclear fuel cycle coming from 239Pu. About three times as much electricity is generated from 239Pu in the United States as from oil-fired electrical generating plants.

The ground state (outer orbital) electronic configuration of Pu is [Rn]5f 67s 2. The most stable oxidation state for plutonium ions in solution is +4, although appreciable amounts of plutonium in its +3, +5, and +6 oxidation states can exist. The aqueous chemistry of plutonium is further complicated by the successive, stepwise hydrolysis of Pu(IV) compounds to form polymers of colloidal dimensions. Plutonium is the transuranium element that is most abundant in the environment, due to the atmospheric testing of nuclear weapons during the 1950s and 1960s that deposited approximately 4.2 tons of plutonium in the environment. Most of this plutonium is in the soil, in which it has no discernable effects. see also Actinium; Berkelium; Einsteinium; Fermium; Lawrencium; Mendelevium; Neptunium; Nobelium; Protactinium; Rutherfordium; Seaborg, Glenn Theodore; Thorium; Uranium. Walter Loveland Seaborg, Glenn T., and Loveland, Walter (1990). The Elements beyond Uranium.

New York: Wiley. Cite this article Plutonium - Element information, properties and uses | Periodic Table Chemistry in its element: plutonium (Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) Chris Smith Hello, this week on Chemistry in its element a substance that most people think is man made but in fact often turns up in the centres of stars. It also packs a huge nuclear punch when it's in the right sort of warhead and also has the power to be a super conductor. The only problem is its radio active and that means that when it decays it tends to fall apart. It is of course Plutonium and here to spell it out is Cambridge University's Ian Farnan. Ian Farnan Plutonium's often billed as the 'most toxic substance known to man'. Just the word plutonium instils a dread in people's minds - And it's the early history of plutonium that established its dark side - and it's a reputation that's been hard to shake-off since.

Glenn Seaborg discovered plutonium at Berkeley in 1940, and in the following spring, when it was found that it could sustain a nuclear chain reaction, he secretly wrote to President Roosevelt, to inform him of that this substance had the potential to be a powerful source of nuclear energy. And from that moment the race was on to produce significant amounts to supply a secret project codenamed the Manhattan Engineering District, the goal of which was to produce a nuclear bomb. Anyone familiar with the iconic image of the mushroom cloud understands the tremendous explosive power of a correctly controlled detonation of plutonium. The energy density is mind-boggling: a sphere of metal 10 cm in diameter and weighing just 8 Kg is enough to produce an explosion at least as big as the one that devastated Nagasaki in 1945. But apart from military uses like this, plutonium also has one of the richest chemistries of any element. There are six different forms of plutonium, known as allotropes, that all exist at different temperatures and behave differently. At room temperature, for instance, the plutonium is very brittle, but heated to around 100 Celsius is transforms to a much more malleable metal.

Scientists have found that they can mimic this effect by adding a small amount of gallium, which gives the room temperature metal similar properties to its higher-temperature counterpart, and this makes it much easier to work with. Mixing plutonium with other metals can also produce substances with other interesting properties. For instance, adding some cobalt and gallium can produce a material that behaves as a super-conductor at low temperatures. Its electrons link up into a close-knit arrangement called Cooper pairs, which allow electricity to flow freely with no resistance. But unfortunately this arrangement doesn't last very long. Because plutonium-239 self destructs, undergoing radioactive decay by spitting out a highly energetic alpha-particle to produce Uranium-235. But as the alpha-particle leaves it causes the uranium nucleus to recoil like a gun that's just been fired, and this damages the structure of the material, disrupting the paired electrons and slowly destroying the superconductivity. So in this sense plutonium is its own worst enemy. Its radioactivity means that it's very difficult to exploit the richness of its chemistry in many compounds, and as its reputation precedes it, plutonium would also have trouble gaining acceptance as a technological material.

But despite its tarnished reputation, some people quite literally have a place in their hearts for plutonium because one of its isotopes, plutonium­-238, generates so much heat when it decays, that it was used as a long-lasting thermoelectric generator in early heart pacemakers. Nowadays it's been replaced by better batteries, but it's still popular with space scientists who use it to power probes sent to explore distant planets far from the Sun, like Cassini, that was sent to Saturn, and New Horizons, which is on its way to Pluto. Plutonium's in a part of the periodic table called the actinide series alongside its neighbours thorium and protoactinium. Seaborg christened the actinides, rearranging the periodic table in the process, on the basis of the unusual arrangements of their electrons, which give these substances unusual magnetic properties, as well as the ability to have multiple oxidation states. Plutonium, for instance, has five, giving it the ability to form an unusually wide range of compounds that scientists are only just beginning to get to grips with.

Some say that plutonium's an evil element created by man, but it's actually a natural element produced by a process known as nucleosynthesis, which takes place in supernova explosions, when dying stars blow themselves to pieces. There isn't much of it on the earth naturally, because the majority of its isotopes have such short half-lives. And in the 4.6 billion years since our solar system began to form, most of them have decayed away to infinitesimally tiny amounts. What there is mostly comes from reactors and nuclear tests. There are severe hazards associated with plutonium, but as with most dangerous materials, these can be mitigated by careful handling and rigorous safeguards. But whatever you think about plutonium, its history, however chequered, has revealed some fascinating chemistry. Although the mushroom cloud remains its best-known image. Chris Smith Ian Farnan, unpacking Plutonium. Next time on Chemistry in its Element the toxic chemical that saves thousands of lives every year.

Peter Wothers In his list of the then known elements, Lavoisier included the term azote meaning the absence of life, but the compound used to explosively fill car air bags with gas is sodium azide, a compound of just Sodium and Nitrogen. When triggered this compound explosively decomposes freeing the Nitrogen gas, which inflates the bags. Far from destroying life, this azotic compound has been responsible for saving thousands. Chris Smith Peter Wothers talking nitrogen on what promises to be an explosive edition of Chemistry in its element next week. I'm Chris Smith, thank you for listening, see you next time. (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com . There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements . (End promo) Facts About Plutonium Facts About Plutonium By Alina Bradford, Live Science Contributor | December 7, 2016 09:30pm ET MORE These buttons of refined plutonium metal were used in the core of the Fat Man bomb dropped on Nagasaki. Credit: U.S.

Department of Energy Plutonium is a radioactive, silver metal that can be used to create or destroy. While it was used for destruction soon after it was made, today the element is used mostly for creating energy throughout the world. Plutonium was first produced and isolated in 1940 and was used to make the "Fat Man" atomic bomb that was dropped on Nagasaki at the end of World War II, just five years after it was first produced, said Amanda Simson, an assistant professor of chemical engineering at the University of New Haven. Just the facts Here are the properties of plutonium, according to the Los Alamos National Laboratory : Atomic number: 94 Melting point: 1,184 F (640 C) Boiling point: 5,842 F (3,228 C) Discovery & history Plutonium was discovered in 1941 by scientists Joseph W. Kennedy, Glenn T. Seaborg, Edward M. McMillan and Arthur C. Wohl at the University of California, Berkley.

The discovery occurred when the team bombarded uranium-238 with deuterons that had been accelerated in a cyclotron device, which created neptunium-238 and two free neutrons. The neptunium-238 then decayed into plutonium-238 through beta decay. This experiment wasn't shared with the rest of the scientific community until 1946, after World War II. Seaborg submitted a paper on their discovery to the journal Physical Review in March 1941, but the paper was removed when it was discovered that an isotope of plutonium, Pu-239, may be used to create an atomic bomb. Soon, Seaborg was sent to lead the Plutonium Production Lab, also known as the Met Lab, at the University of Chicago, according to the Los Alamos National Laboratory. The purpose of the lab was to create plutonium as part of the Manhattan Project. The Manhattan Project was a secret venture during World War II that worked exclusively to develop an atomic bomb. On August 18, 1942, they had their first big success. They were able to create a trace quantity of plutonium that was visible to the eye.

It equaled only around 1 microgram. From the tiny sample, scientist determined plutonium's atomic weight. The Manhattan Project eventually produced enough plutonium for the "Trinity Test." During the test, the world's first atomic bomb, or the "The Gadget," was exploded near Socorro, New Mexico, on July 16, 1945, by Los Alamos Laboratory director Robert Oppenheimer and Army General Leslie Groves. Of the test, Oppenheimer said, "We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita. Vishnu is trying to persuade the Prince that he should do his duty and to impress him takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds.' I suppose we all thought that, one way or another," according to the Royal Society of Chemistry . The explosion had the energy equivalent of approximately 20,000 tons of TNT. The first war-use atomic bomb dropped on Hiroshima, Japan, on August 6, 1945.

That atomic bomb, dubbed "Little Boy," had a uranium core, though. The second bomb, dropped on Nagasaki, Japan, in August 9, 1945, had a plutonium core. The "Fat Man," as it was called, hastened the end of World War II. Properties of plutonium Freshly prepared plutonium metal has a silvery bright color but takes on a dull gray, yellow, or olive green tarnish when oxidized in air. The metal quickly dissolves in concentrated mineral acids. A large piece of plutonium feels warm to the touch because of the energy given off by alpha decay; larger pieces can produce enough heat to boil water. At room temperature alpha-form plutonium (the most common form) is as hard and brittle as cast iron. It can be alloyed with other metals to form the room-temperature stabilized delta form, which is soft and ductile. Unlike most metals, plutonium is not a good conductor of heat or electricity. It has a low melting point and an unusually high boiling point. Plutonium can form alloys and intermediate compounds with most other metals, and compounds with a variety of other elements. Some alloys have superconductive abilities and others are used to make nuclear fuel pellets.

Its compounds come in a variety of colors, depending on the oxidation state and how complex various ligands are. In aqueous solution there are five valance ionic states. Plutonium, along with all of the other transuranium elements, is a radiological hazard and must be handled with specialized equipment and precautions. Animal studies have found that a few milligrams of plutonium per kilogram of tissue are lethal. Sources Plutonium generally isn't found in nature. Trace elements of plutonium are found in naturally occurring uranium ores. Here, it is formed in a way similar to neptunium: by irradiation of natural uranium with neutrons followed by beta decay. Primarily, however, plutonium is a byproduct of the nuclear power industry. Each year, around 20 tons of plutonium is produced, according to the Los Alamos National Laboratory. Spent nuclear fuel can also be reprocessed to separate usable plutonium from other elements in the fuel. Atmospheric weapons testing in the 1950s and 1960s left tons of plutonium in the Earth's atmosphere that is still there today, according to the World Nuclear Association . Uses For the most part, plutonium isn't used for much.

In fact, of the five common isotopes, only two of plutonium's isotopes, plutonium-238 and plutonium-239, are used for anything at all. Plutonium-238 is used to make electricity for space probes using radioisotope thermoelectric generators. These generators are switched on when the probes can't get enough solar power because they have traveled too far away from the sun. Some probes that use plutonium-238 are Cassini and Galileo. When concentrated enough, plutonium-239 undergoes a fission chain reaction. Because of this, it is used in nuclear weapons and some nuclear reactors. In fact, one of the biggest uses for plutonium is energy. According to the World Nuclear Association, over one-third of the energy produced in most nuclear power plants comes from plutonium. Plutonium is the main fuel in fast neutron reactors. Who knew? For decades, scientists wondered why plutonium didn't act like other metals in its group. For instance, plutonium is a poor conductor of electricity and it doesn't stick to magnets.

Now researchers have figured out where its "missing magnetism" has been hiding out and it has to do with the wacky behavior of the electrons in the element's outer shell. Unlike other metals, which have a set number of electrons in their outer shells, when in a ground state, plutonium can have four, five or six electrons there. This fluctuating number of outer-shell electrons explains why plutonium isn't magnetic: In order for an atom to interact with magnets the unpaired electrons in its outer shell must line up in a magnetic field. [ Read more about plutonium's missing magnetism ] Plutonium's most stable isotope, plutonium-244, can last a long time. It has a half-life of about 82 million years and decays into uranium-240 through alpha decay, according to the Jefferson Lab . Plutonium was named after the planet, Pluto. This is because it came after Uranium, which was named after the planet Uranus, and neptunium, which was named after the planet Neptune. Plutonium emits neutrons, beta particles and gamma rays.

Additional resources Synthetic elements | Article about synthetic elements by The Free Dictionary Synthetic elements | Article about synthetic elements by The Free Dictionary Also found in: Wikipedia . synthetic elements, in chemistry, radioactive elements that were not discovered occurring in nature but as artificially produced isotopes. They are technetium technetium [Gr. technetos=artificial], artificially produced radioactive chemical element; symbol Tc; at. no. 43; mass no. of most stable isotope 98; m.p. 2,200&degC;; b.p. 4,877&degC;; sp. gr. 11.5 (calculated); valence +4, +6, or +7. ..... Click the link for more information. (at. no. 43), which was the first element to be synthesized, promethium promethium , artificially produced radioactive chemical element; symbol Pm; at. no. 61; mass no. of most stable isotope 145; m.p. 1,042&degC;; b.p. 3,000&degC; (estimated); sp. gr. unknown; valence +3. ..... Click the link for more information.

(at. no. 61), astatine astatine [Gr.,=unstable], semimetallic radioactive chemical element; symbol At; at. no. 85; at. wt. of most stable isotope 210; m.p. 302&degC; (estimated); b.p. 337&degC; (estimated); density unknown; valence believed to be +1, +3, +5, or +7. ..... Click the link for more information. (at. no. 85), francium francium [from France], radioactive chemical element; symbol Fr; at. no. 87; mass no. of most stable isotope 223; m.p. about 27&degC; (estimated); b.p. 677&degC; (estimated); sp. gr. unknown; valence +1. ..... Click the link for more information. (at. no. 87), and the transuranium elements transuranium elements, in chemistry, radioactive elements with atomic numbers greater than that of uranium (at. no. 92).

All the transuranium elements of the actinide series were discovered as synthetic radioactive isotopes at the Univ. ..... Click the link for more information. (at. no. 93 and beyond in the periodic table periodic table, chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled ..... Click the link for more information. ). Some of these elements have since been shown to exist in minute amounts in nature, usually as short-lived members of natural radioactive decay series (see radioactivity radioactivity, spontaneous disintegration or decay of the nucleus of an atom by emission of particles, usually accompanied by electromagnetic radiation. The energy produced by radioactivity has important military and industrial applications. ..... Click the link for more information. ). The synthetic elements through at. no. 100 ( fermium fermium [for Enrico Fermi], artificially produced radioactive chemical element; symbol Fm; at. no. 100; mass no. of most stable isotope 257; m.p. 1,527&degC;; b.p.

and sp. gr. unknown; valence +2, +3. Fermium is a member of Group 3 of the periodic table. ..... Click the link for more information. ) are created by bombarding a heavy element, such as uranium or plutonium, with neutrons or alpha particles. The synthesis of the transfermium elements (elements with at. no. 101 or greater) is accomplished by the fusion of the nuclei of two lighter elements. Elements 101 through 106 were first produced by fusing the nuclei of slightly lighter elements, such as californium californium [from California], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900&degC;; b.p. about 1,470&degC;; density unknown; valence +3. ..... Click the link for more information. , with those of light elements, such as carbon carbon [Lat.,=charcoal], nonmetallic chemical element; symbol C; at. no. 6; interval in which at. wt.

ranges 12.0096–12.0116; m.p. about 3,550&degC;; graphite sublimes about 3,375&degC;; b.p. 4,827&degC;; sp. gr. 1.8–2.1 (amorphous), 1.9–2.3 (graphite), 3. ..... Click the link for more information. . Elements 107 through 112 were first produced by fusing the nuclei of medium-weight elements, such as bismuth bismuth [Ger. Weisse Masse=white mass], metallic chemical element; symbol Bi; at. no. 83; at. wt. 208.98040; m.p. 271.3&degC;; b.p. about 1,560&degC;; sp. gr. 9.75 at 20&degC;; valence +3 or +5. ..... Click the link for more information. or lead lead, metallic chemical element; symbol Pb [Lat. plumbum]; at. no. 82; at. wt.

207.2; m.p. 327.502&degC;; b.p. about 1,740&degC;; sp. gr. 11.35 at 20&degC;; valence +2 or +4. ..... Click the link for more information. , with those of other medium-weight elements, such as iron iron, metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535&degC;; b.p. about 2,750&degC;; sp. gr. 7.87 at 20&degC;; valence +2, +3, +4, or +6. Iron is biologically significant. ..... Click the link for more information. , nickel nickel, metallic chemical element; symbol Ni; at. no. 28; at. wt. 58.6934; m.p. about 1,453&degC;; b.p. about 2,732&degC;; sp. gr.

8.902 at 25&degC;; valence 0, +1, +2, +3, or +4. ..... Click the link for more information. , or zinc zinc, metallic chemical element; symbol Zn; at. no. 30; at. wt. 65.38; m.p. 419.58&degC;; b.p. 907&degC;; sp. gr. 7.133 at 25&degC;; valence +2. Zinc is a lustrous bluish-white metal. It is found in Group 12 of the periodic table. ..... Click the link for more information. . Of the elements greater than 112 whose creation has been officially confirmed, element 114 was discovered by fusing the nuclei of plutonium plutonium , radioactive chemical element; symbol Pu; at. no. 94; mass no. of most stable isotope 244; m.p. 641&degC;; b.p. 3,232&degC;; sp. gr.

19.84 at 20&degC;; valence +3, +4, +5, or +6. ..... Click the link for more information. and calcium calcium [Lat.,=lime], metallic chemical element; symbol Ca; at. no. 20; at. wt. 40.078; m.p. about 839&degC;; b.p. 1,484&degC;; sp. gr. 1.55 at 20&degC;; valence +2. Calcium is a malleable, ductile, silver-white, relatively soft metal with face-centered, cubic crystalline ..... Click the link for more information. , and element 116 using curium curium , artificially produced radioactive chemical element; symbol Cm; at. no. 96; mass no. of most stable isotope 247; m.p. about 1,340&degC;; b.p. 3,110&degC;; sp. gr. 13.5 (calculated); valence +3, +4. ..... Click the link for more information. and calcium.

The transfermium elements are produced in very small quantities (one atom at a time), and identification is therefore very difficult because of half-lives half-life, measure of the average lifetime of a radioactive substance (see radioactivity) or an unstable subatomic particle. One half-life is the time required for one half of any given quantity of the substance to decay. ..... Click the link for more information. ranging from minutes to milliseconds and the need to identify the products by methods other than known chemical separations. This has led to controversy over reported discoveries and over the naming of the elements. It has been predicted that one isotope of element 114—containing 114 protons and 184 neutrons—would be very stable because its nucleus would have a full complement of protons and neutrons. Termed an "island of stability," its half-life might be measured in years. However, none of the isotopes of element 114 synthesized as yet have as many as 184 neutrons, and their half-lives are still in the millisecond range (see flerovium flerovium, artificially produced radioactive chemical element; symbol Fl; at. no.

114; mass number of most stable isotope 289; m.p., b.p., sp. gr., and valence unknown. Situated in Group 14 of the periodic table, it is expected to have properties similar to those of lead and tin. ..... Click the link for more information. ).

Question: Element 94, first synthesized in 1940, was given what name?
Answer: PLUTONIUM