Californium

Last updated

Californium, 98Cf
Californium.jpg
Californium
Pronunciation /ˌkæləˈfɔːrniəm/ ​(KAL-ə-FOR-nee-əm)
Appearancesilvery
Mass number [251]
Californium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Dy
↑
Cf
↓
—
berkelium ← californium → einsteinium
Atomic number (Z)98
Group f-block groups (no number)
Period period 7
Block   f-block
Electron configuration [ Rn ] 5f10 7s2 [1]
Electrons per shell2, 8, 18, 32, 28, 8, 2
Physical properties
Phase at  STP solid
Melting point 1173  K ​(900 °C,​1652 °F) [2]
Boiling point 1743 K​(1470 °C,​2678 °F)(estimation) [3]
Density (near  r.t.)15.1 g/cm3 [2]
Atomic properties
Oxidation states +2, +3, +4, +5 [4] [5]
Electronegativity Pauling scale: 1.3 [6]
Ionization energies
  • 1st: 608 kJ/mol [7]
Californium spectrum visible.png
Spectral lines of californium
Other properties
Natural occurrence synthetic
Crystal structure ​ double hexagonal close-packed (dhcp)
Hexagonal.svg
Mohs hardness 3–4 [8]
CAS Number 7440-71-3 [2]
History
Namingafter California, where it was discovered
Discovery Lawrence Berkeley National Laboratory (1950)
Isotopes of californium
Main isotopes [9] [10] Decay
abun­dance half-life (t1/2) mode pro­duct
248Cf synth 333.5 d α 100% 244Cm
SF <0.01%–
249Cfsynth351 yα100% 245Cm
SF≪0.01%–
250Cfsynth13.08 yα99.9% 246Cm
SF0.08%–
251Cfsynth898 yα 247Cm
252Cfsynth2.645 yα96.9% 248Cm
SF3.09%–
253Cfsynth17.81 d β− 99.7% 253Es
α0.31% 249Cm
254Cfsynth60.5 dSF99.7%–
α0.31% 250Cm
Symbol category class.svg  Category: Californium
| references

Californium is a synthetic chemical element; it has symbol Cf and atomic number 98. It was first synthesized in 1950 at Lawrence Berkeley National Laboratory [11] (then the University of California Radiation Laboratory) by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all elements that have been produced in amounts large enough to see with the naked eye (after einsteinium). It was named after the university and the U.S. state of California.

Contents

Two crystalline forms exist at normal pressure: one above and one below 900 °C (1,650 °F). A third form exists at high pressure. Californium slowly tarnishes in air at room temperature. Californium compounds are dominated by the +3 oxidation state. The most stable of californium's twenty known isotopes is californium-251, with a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust. [lower-alpha 1] 252Cf, with a half-life of about 2.645 years, is the most common isotope used and is produced at Oak Ridge National Laboratory (ORNL) in the United States and Research Institute of Atomic Reactors in Russia.

Californium is one of the few transuranium elements with practical uses. Most of these applications exploit the fact that certain isotopes of californium emit neutrons. For example, californium can be used to help start up nuclear reactors, and it is used as a source of neutrons when studying materials using neutron diffraction and neutron spectroscopy. It can also be used in nuclear synthesis of higher mass elements; oganesson (element 118) was synthesized by bombarding californium-249 atoms with calcium-48 ions. Users of californium must take into account radiological concerns and the element's ability to disrupt the formation of red blood cells by bioaccumulating in skeletal tissue.

Characteristics

Physical properties

Californium is a silvery-white actinide metal [12] with a melting point of 900 ± 30 °C (1,650 ± 50 °F) and an estimated boiling point of 1,743 K (1,470 °C; 2,680 °F). [13] The pure metal is malleable and is easily cut with a knife. Californium metal starts to vaporize above 300 °C (570 °F) when exposed to a vacuum. [14] Below 51 K (−222 °C; −368 °F) californium metal is either ferromagnetic or ferrimagnetic (it acts like a magnet), between 48 and 66 K it is antiferromagnetic (an intermediate state), and above 160 K (−113 °C; −172 °F) it is paramagnetic (external magnetic fields can make it magnetic). [15] It forms alloys with lanthanide metals but little is known about the resulting materials. [14]

The element has two crystalline forms at standard atmospheric pressure: a double-hexagonal close-packed form dubbed alpha (α) and a face-centered cubic form designated beta (β). [lower-alpha 2] The α form exists below 600–800°C with a density of 15.10 g/cm3 and the β form exists above 600–800°C with a density of 8.74 g/cm3. [17] At 48  GPa of pressure the β form changes into an orthorhombic crystal system due to delocalization of the atom's 5f electrons, which frees them to bond. [18] [lower-alpha 3]

The bulk modulus of a material is a measure of its resistance to uniform pressure. Californium's bulk modulus is 50±5 GPa, which is similar to trivalent lanthanide metals but smaller than more familiar metals, such as aluminium (70 GPa). [18]

Chemical properties and compounds

Representative californium compounds [12] [lower-alpha 4]
statecompoundformulacolor
+2 californium(II) bromide CfBr2yellow
+2 californium(II) iodide CfI2dark violet
+3 californium(III) oxide Cf2O3yellow-green
+3 californium(III) fluoride CfF3bright green
+3 californium(III) chloride CfCl3emerald green
+3 californium(III) bromide CfBr3yellowish green
+3 californium(III) iodide CfI3lemon yellow
+3 californium(III) polyborate Cf[B6O8(OH)5]pale green
+4 californium(IV) oxide CfO2black brown
+4 californium(IV) fluoride CfF4green

Californium exhibits oxidation states of 4, 3, or 2. It typically forms eight or nine bonds to surrounding atoms or ions. Its chemical properties are predicted to be similar to other primarily 3+ valence actinide elements [20] and the element dysprosium, which is the lanthanide above californium in the periodic table. [21] Compounds in the +4 oxidation state are strong oxidizing agents and those in the +2 state are strong reducing agents. [12]

The element slowly tarnishes in air at room temperature, with the rate increasing when moisture is added. [17] Californium reacts when heated with hydrogen, nitrogen, or a chalcogen (oxygen family element); reactions with dry hydrogen and aqueous mineral acids are rapid. [17]

Californium is only water-soluble as the californium(III) cation. Attempts to reduce or oxidize the +3 ion in solution have failed. [21] The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate, or hydroxide. [20] Californium is the heaviest actinide to exhibit covalent properties, as is observed in the californium borate. [22]

Isotopes

Twenty isotopes of californium are known (mass number ranging from 237 to 256 [10] ); the most stable are 251Cf with half-life 898 years, 249Cf with half-life 351 years, 250Cf at 13.08 years, and 252Cf at 2.645 years. [10] All other isotopes have half-life shorter than a year, and most of these have half-lives less than 20 minutes. [10]

249Cf is formed by beta decay of berkelium-249, and most other californium isotopes are made by subjecting berkelium to intense neutron radiation in a nuclear reactor. [21] Though californium-251 has the longest half-life, its production yield is only 10% due to its tendency to collect neutrons (high neutron capture) and its tendency to interact with other particles (high neutron cross section). [23]

252Cf is a very strong neutron emitter, which makes it extremely radioactive and harmful. [24] [25] [26] 252Cf, 96.9% of the time, alpha decays to curium-248; the other 3.1% of decays are spontaneous fission. [10] One microgram (μg) of 252Cf emits 2.3 million neutrons per second, an average of 3.7 neutrons per spontaneous fission. [27] Most other isotopes of californium, alpha decay to curium (atomic number 96). [10]

History

The 60-inch-diameter (1.52 m) cyclotron used to first synthesize californium Berkeley 60-inch cyclotron.jpg
The 60-inch-diameter (1.52 m) cyclotron used to first synthesize californium

Californium was first made at University of California Radiation Laboratory, Berkeley, by physics researchers Stanley Gerald Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn T. Seaborg, about February 9, 1950. [28] It was the sixth transuranium element to be discovered; the team announced its discovery on March 17, 1950. [29] [30]

To produce californium, a microgram-size target of curium-242 (242
96Cm
) was bombarded with 35 MeV alpha particles (4
2He
) in the 60-inch-diameter (1.52 m) cyclotron at Berkeley, which produced californium-245 (245
98Cf
) plus one free neutron (
n
). [28] [29]

242
96Cm
 + 4
2He
 → 245
98Cf
 + 1
0
n

To identify and separate out the element, ion exchange and adsorsion methods were undertaken. [29] [31] Only about 5,000 atoms of californium were produced in this experiment, [32] and these atoms had a half-life of 44 minutes. [28]

The discoverers named the new element after the university and the state. This was a break from the convention used for elements 95 to 97, which drew inspiration from how the elements directly above them in the periodic table were named. [33] [lower-alpha 5] However, the element directly above element 98 in the periodic table, dysprosium, has a name that means "hard to get at", so the researchers decided to set aside the informal naming convention. [35] They added that "the best we can do is to point out [that] ... searchers a century ago found it difficult to get to California". [34]

Weighable amounts of californium were first produced by the irradiation of plutonium targets at Materials Testing Reactor at National Reactor Testing Station, eastern Idaho; these findings were reported in 1954. [36] The high spontaneous fission rate of californium-252 was observed in these samples. The first experiment with californium in concentrated form occurred in 1958. [28] The isotopes 249Cf to 252Cf were isolated that same year from a sample of plutonium-239 that had been irradiated with neutrons in a nuclear reactor for five years. [12] Two years later, in 1960, Burris Cunningham and James Wallman of Lawrence Radiation Laboratory of the University of California created the first californium compounds—californium trichloride, californium(III) oxychloride, and californium oxide—by treating californium with steam and hydrochloric acid. [37]

The High Flux Isotope Reactor (HFIR) at ORNL in Oak Ridge, Tennessee, started producing small batches of californium in the 1960s. [38] By 1995, HFIR nominally produced 500 milligrams (0.018 oz) of californium annually. [39] Plutonium supplied by the United Kingdom to the United States under the 1958 US–UK Mutual Defence Agreement was used for making californium. [40]

The Atomic Energy Commission sold 252Cf to industrial and academic customers in the early 1970s for $10/microgram, [27] and an average of 150 mg (0.0053 oz) of 252Cf were shipped each year from 1970 to 1990. [41] [lower-alpha 6] Californium metal was first prepared in 1974 by Haire and Baybarz, who reduced californium(III) oxide with lanthanum metal to obtain microgram amounts of sub-micrometer thick films. [42] [43] [lower-alpha 7]

Occurrence

Traces of californium can be found near facilities that use the element in mineral prospecting and in medical treatments. [45] The element is fairly insoluble in water, but it adheres well to ordinary soil; and concentrations of it in the soil can be 500 times higher than in the water surrounding the soil particles. [46]

Nuclear fallout from atmospheric nuclear weapons testing prior to 1980 contributed a small amount of californium to the environment. [46] Californium-249, -252, -253, and -254 have been observed in the radioactive dust collected from the air after a nuclear explosion. [47] Californium is not a major radionuclide at United States Department of Energy legacy sites since it was not produced in large quantities. [46]

Californium was once believed to be produced in supernovas, as their decay matches the 60-day half-life of 254Cf. [48] However, subsequent studies failed to demonstrate any californium spectra, [49] and supernova light curves are now thought to follow the decay of nickel-56. [50]

The transuranic elements americium to fermium, including californium, occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so. [51]

Spectral lines of californium, along with those of several other non-primordial elements, were detected in Przybylski's Star in 2008. [52]

Production

Californium is produced in nuclear reactors and particle accelerators. [53] Californium-250 is made by bombarding berkelium-249 (249Bk) with neutrons, forming berkelium-250 (250Bk) via neutron capture (n,γ) which, in turn, quickly beta decays (β−) to californium-250 (250Cf) in the following reaction: [54]

249
97Bk
(n,γ)250
97Bk
 → 250
98Cf
 + β−

Bombardment of 250Cf with neutrons produces 251Cf and 252Cf. [54]

Prolonged irradiation of americium, curium, and plutonium with neutrons produces milligram amounts of 252Cf and microgram amounts of 249Cf. [55] As of 2006, curium isotopes 244 to 248 are irradiated by neutrons in special reactors to produce mainly californium-252 with lesser amounts of isotopes 249 to 255. [56]

Microgram quantities of 252Cf are available for commercial use through the U.S. Nuclear Regulatory Commission. [53] Only two sites produce 252Cf: Oak Ridge National Laboratory in the U.S., and the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. As of 2003, the two sites produce 0.25 grams and 0.025 grams of 252Cf per year, respectively. [57]

Three californium isotopes with significant half-lives are produced, requiring a total of 15 neutron captures by uranium-238 without nuclear fission or alpha decay occurring during the process. [57] 253Cf is at the end of a production chain that starts with uranium-238, and includes several isotopes of plutonium, americium, curium, and berkelium, and the californium isotopes 249 to 253 (see diagram).

Scheme of the production of californium-252 from uranium-238 by neutron irradiation Cf 252 Produktion.png
Scheme of the production of californium-252 from uranium-238 by neutron irradiation

Applications

Fifty-ton shipping cask built at ORNL which can transport up to 1 gram of Cf. Large and heavily shielded transport containers are needed to prevent the release of highly radioactive material in case of normal and hypothetical accidents. CfShield.JPG
Fifty-ton shipping cask built at ORNL which can transport up to 1 gram of Cf. Large and heavily shielded transport containers are needed to prevent the release of highly radioactive material in case of normal and hypothetical accidents.

Californium-252 has a number of specialized uses as a strong neutron emitter; it produces 139 million neutrons per microgram per minute. [27] This property makes it useful as a startup neutron source for some nuclear reactors [17] and as a portable (non-reactor based) neutron source for neutron activation analysis to detect trace amounts of elements in samples. [60] [lower-alpha 8] Neutrons from californium are used as a treatment of certain cervical and brain cancers where other radiation therapy is ineffective. [17] It has been used in educational applications since 1969 when Georgia Institute of Technology got a loan of 119 μg of 252Cf from the Savannah River Site. [62] It is also used with online elemental coal analyzers and bulk material analyzers in the coal and cement industries.

Neutron penetration into materials makes californium useful in detection instruments such as fuel rod scanners; [17] neutron radiography of aircraft and weapons components to detect corrosion, bad welds, cracks and trapped moisture; [63] and in portable metal detectors. [64] Neutron moisture gauges use 252Cf to find water and petroleum layers in oil wells, as a portable neutron source for gold and silver prospecting for on-the-spot analysis, [21] and to detect ground water movement. [65] The main uses of 252Cf in 1982 were, reactor start-up (48.3%), fuel rod scanning (25.3%), and activation analysis (19.4%). [66] By 1994, most 252Cf was used in neutron radiography (77.4%), with fuel rod scanning (12.1%) and reactor start-up (6.9%) as important but secondary uses. [66] In 2021, fast neutrons from 252Cf were used for wireless data transmission. [67]

251Cf has a very small calculated critical mass of about 5 kg (11 lb), [68] high lethality, and a relatively short period of toxic environmental irradiation. The low critical mass of californium led to some exaggerated claims about possible uses for the element. [lower-alpha 9]

In October 2006, researchers announced that three atoms of oganesson (element 118) had been identified at Joint Institute for Nuclear Research in Dubna, Russia, from bombarding 249Cf with calcium-48, making it the heaviest element ever made. The target contained about 10 mg of 249Cf deposited on a titanium foil of 32 cm2 area. [70] [71] [72] Californium has also been used to produce other transuranic elements; for example, lawrencium was first synthesized in 1961 by bombarding californium with boron nuclei. [73]

Precautions

Californium that bioaccumulates in skeletal tissue releases radiation that disrupts the body's ability to form red blood cells. [74] The element plays no natural biological role in any organism due to its intense radioactivity and low concentration in the environment. [45]

Californium can enter the body from ingesting contaminated food or drinks or by breathing air with suspended particles of the element. Once in the body, only 0.05% of the californium will reach the bloodstream. About 65% of that californium will be deposited in the skeleton, 25% in the liver, and the rest in other organs, or excreted, mainly in urine. Half of the californium deposited in the skeleton and liver are gone in 50 and 20 years, respectively. Californium in the skeleton adheres to bone surfaces before slowly migrating throughout the bone. [46]

The element is most dangerous if taken into the body. In addition, californium-249 and californium-251 can cause tissue damage externally, through gamma ray emission. Ionizing radiation emitted by californium on bone and in the liver can cause cancer. [46]

Notes

  1. ↑ The Earth formed 4.5 billion years ago, and the extent of natural neutron emission within it that could produce californium from more stable elements is extremely limited.
  2. ↑ A double hexagonal close-packed (dhcp) unit cell consists of two hexagonal close-packed structures that share a common hexagonal plane, giving dhcp an ABACABAC sequence. [16]
  3. ↑ The three lower-mass transplutonium elements—americium, curium, and berkelium—require much less pressure to delocalize their 5f electrons. [18]
  4. ↑ Other +3 oxidation states include the sulfide and metallocene. [19]
  5. ↑ Europium, in the sixth period directly above element 95, was named for the continent it was discovered on, so element 95 was named americium. Element 96 was named curium for Marie Curie and Pierre Curie as an analog to the naming of gadolinium, which was named for the scientist and engineer Johan Gadolin. Terbium was named for the village it was discovered in, so element 97 was named berkelium. [34]
  6. ↑ The Nuclear Regulatory Commission replaced the Atomic Energy Commission when the Energy Reorganization Act of 1974 was implemented. The price of californium-252 was increased by the NRC several times and was $60 per microgram by 1999; this price does not include the cost of encapsulation and transportation. [27]
  7. ↑ In 1975, another paper stated that the californium metal prepared the year before was the hexagonal compound Cf2O2S and face-centered cubic compound CfS. [44] The 1974 work was confirmed in 1976 and work on californium metal continued. [42]
  8. ↑ By 1990, californium-252 had replaced plutonium-beryllium neutron sources due to its smaller size and lower heat and gas generation. [61]
  9. ↑ An article entitled "Facts and Fallacies of World War III" in the July 1961 edition of Popular Science magazine read "A californium atomic bomb need be no bigger than a pistol bullet. You could build a hand-held six-shooter to fire bullets that would explode on contact with the force of 10 tons of TNT." [69]

Related Research Articles

<span class="mw-page-title-main">Americium</span> Chemical element with atomic number 95 (Am)

Americium is a synthetic chemical element; it has symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element europium and was thus named after the Americas by analogy.

The actinide or actinoid series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium. The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.

<span class="mw-page-title-main">Berkelium</span> Chemical element with atomic number 97 (Bk)

Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

<span class="mw-page-title-main">Curium</span> Chemical element with atomic number 96 (Cm)

Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.

<span class="mw-page-title-main">Einsteinium</span> Chemical element with atomic number 99 (Es)

Einsteinium is a synthetic chemical element; it has symbol Es and atomic number 99. It is named after Albert Einstein and is a member of the actinide series and is the seventh transuranium element.

Fermium is a synthetic chemical element; it has symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared. A total of 20 isotopes are known, with 257Fm being the longest-lived with a half-life of 100.5 days.

<span class="mw-page-title-main">Glenn T. Seaborg</span> American chemist (1912–1999)

Glenn Theodore Seaborg was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work in this area also led to his development of the actinide concept and the arrangement of the actinide series in the periodic table of the elements.

Nobelium is a synthetic chemical element; it has symbol No and atomic number 102. It is named after Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the tenth transuranium element and is the penultimate member of the actinide series. Like all elements with atomic number over 100, nobelium can only be produced in particle accelerators by bombarding lighter elements with charged particles. A total of twelve nobelium isotopes are known to exist; the most stable is 259No with a half-life of 58 minutes, but the shorter-lived 255No is most commonly used in chemistry because it can be produced on a larger scale.

<span class="mw-page-title-main">Synthetic element</span> Chemical elements that do not occur naturally

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: 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 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.

The transuranium elements are the chemical elements with atomic numbers greater than 92, which is the atomic number of uranium. All of them are radioactively unstable and decay into other elements. With the exception of neptunium and plutonium which have been found in trace amounts in nature, none occur naturally on Earth and they are synthetic.

A period 7 element is one of the chemical elements in the seventh row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases: a new row is begun when chemical behavior begins to repeat, meaning that elements with similar behavior fall into the same vertical columns. The seventh period contains 32 elements, tied for the most with period 6, beginning with francium and ending with oganesson, the heaviest element currently discovered. As a rule, period 7 elements fill their 7s shells first, then their 5f, 6d, and 7p shells in that order, but there are exceptions, such as uranium.

Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being plutonium-238 in 1940. Twenty plutonium radioisotopes have been characterized. The most stable 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; and plutonium-240 with a half-life of 6,560 years. This element also has eight meta states; all have half-lives of less than one second.

Californium (98Cf) is an artificial element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 245Cf in 1950. There are 20 known radioisotopes ranging from 237Cf to 256Cf and one nuclear isomer, 249mCf. The longest-lived isotope is 251Cf with a half-life of 898 years.

<span class="mw-page-title-main">Minor actinide</span> Category of elements in spent nuclear fuel

A minor actinide is an actinide, other than uranium or plutonium, found in spent nuclear fuel. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium. The most important isotopes of these elements in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.

<span class="mw-page-title-main">Actinides in the environment</span>

The actinide series is a group of chemical elements with atomic numbers ranging from 89 to 102, including notable elements such as uranium and plutonium. The nuclides thorium-232, uranium-235, and uranium-238 occur primordially, while trace quantities of actinium, protactinium, neptunium, and plutonium exist as a result of radioactive decay and neutron capture of uranium. These elements are far more radioactive than the naturally occurring thorium and uranium, and thus have much shorter half-lives. Elements with atomic numbers greater than 94 do not exist naturally on Earth, and must be produced in a nuclear reactor. However, certain isotopes of elements up to californium still have practical applications which take advantage of their radioactive properties.

Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like some other plutonium isotopes, 241Pu is fissile, with a neutron absorption cross section about one-third greater than that of 239Pu, and a similar probability of fissioning on neutron absorption, around 73%. In the non-fission case, neutron capture produces plutonium-242. In general, isotopes with an odd number of neutrons are both more likely to absorb a neutron and more likely to undergo fission on neutron absorption than isotopes with an even number of neutrons.

Plutonium-242 is one of the isotopes of plutonium, the second longest-lived, with a half-life of 375,000 years. The half-life of 242Pu is about 15 times that of 239Pu; so it is one-fifteenth as radioactive, and not one of the larger contributors to nuclear waste radioactivity. 242Pu's gamma ray emissions are also weaker than those of the other isotopes.

Long-lived fission products (LLFPs) are radioactive materials with a long half-life produced by nuclear fission of uranium and plutonium. Because of their persistent radiotoxicity, it is necessary to isolate them from humans and the biosphere and to confine them in nuclear waste repositories for geological periods of time. The focus of this article is radioisotopes (radionuclides) generated by fission reactors.

<span class="mw-page-title-main">Nuclear transmutation</span> Conversion of an atom from one element to another

Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed.

<span class="mw-page-title-main">Berkelium compounds</span> Chemical compounds

Berkelium forms a number of chemical compounds, where it normally exists in an oxidation state of +3 or +4, and behaves similarly to its lanthanide analogue, terbium. Like all actinides, berkelium easily dissolves in various aqueous inorganic acids, liberating gaseous hydrogen and converting into the trivalent oxidation state. This trivalent state is the most stable, especially in aqueous solutions, but tetravalent berkelium compounds are also known. The existence of divalent berkelium salts is uncertain and has only been reported in mixed lanthanum chloride-strontium chloride melts. Aqueous solutions of Bk3+ ions are green in most acids. The color of the Bk4+ ions is yellow in hydrochloric acid and orange-yellow in sulfuric acid. Berkelium does not react rapidly with oxygen at room temperature, possibly due to the formation of a protective oxide surface layer; however, it reacts with molten metals, hydrogen, halogens, chalcogens and pnictogens to form various binary compounds. Berkelium can also form several organometallic compounds.

References

  1. ↑ CRC 2006, p. 1.14.
  2. 1 2 3 CRC 2006, p. 4.56.
  3. ↑ Joseph Jacob Katz; Glenn Theodore Seaborg; Lester R. Morss (1986). The Chemistry of the actinide elements. Chapman and Hall. p. 1038. ISBN   9780412273704 . Retrieved July 11, 2011.
  4. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1265. ISBN   978-0-08-037941-8.
  5. ↑ Kovács, Attila; Dau, Phuong D.; Marçalo, Joaquim; Gibson, John K. (2018). "Pentavalent Curium, Berkelium, and Californium in Nitrate Complexes: Extending Actinide Chemistry and Oxidation States". Inorg. Chem. 57 (15). American Chemical Society: 9453–9467. doi:10.1021/acs.inorgchem.8b01450. OSTI   1631597. PMID   30040397. S2CID   51717837.
  6. ↑ Emsley 1998, p. 50.
  7. ↑ CRC 2006, p. 10.204.
  8. ↑ CRC 1991, p. 254.
  9. ↑ CRC 2006, p. 11.196.
  10. 1 2 3 4 5 6 Sonzogni, Alejandro A. (Database Manager), ed. (2008). "Chart of Nuclides". National Nuclear Data Center, Brookhaven National Laboratory. Retrieved March 1, 2010.
  11. ↑ "Californium (Cf) | AMERICAN ELEMENTS ®". American Elements: The Materials Science Company. Retrieved November 30, 2023.
  12. 1 2 3 4 Jakubke 1994, p. 166.
  13. ↑ Haire 2006, pp. 1522–1523.
  14. 1 2 Haire 2006, p. 1526.
  15. ↑ Haire 2006, p. 1525.
  16. ↑ Szwacki 2010, p. 80.
  17. 1 2 3 4 5 6 O'Neil 2006, p. 276.
  18. 1 2 3 Haire 2006, p. 1522.
  19. ↑ Cotton et al. 1999, p. 1163.
  20. 1 2 Seaborg 2004.
  21. 1 2 3 4 CRC 2006, p. 4.8.
  22. ↑ Polinski, Matthew J.; Iii, Edward B. Garner; Maurice, Rémi; Planas, Nora; Stritzinger, Jared T.; Parker, T. Gannon; Cross, Justin N.; Green, Thomas D.; Alekseev, Evgeny V. (May 1, 2014). "Unusual structure, bonding and properties in a californium borate". Nature Chemistry. 6 (5): 387–392. Bibcode:2014NatCh...6..387P. CiteSeerX   10.1.1.646.749 . doi:10.1038/nchem.1896. ISSN   1755-4330. PMID   24755589. S2CID   104331283.
  23. ↑ Haire 2006, p. 1504.
  24. ↑ Hicks, D. A.; Ise, John; Pyle, Robert V. (1955). "Multiplicity of Neutrons from the Spontaneous Fission of Californium-252". Physical Review. 97 (2): 564–565. Bibcode:1955PhRv...97..564H. doi:10.1103/PhysRev.97.564.
  25. ↑ Hicks, D. A.; Ise, John; Pyle, Robert V. (1955). "Spontaneous-Fission Neutrons of Californium-252 and Curium-244". Physical Review. 98 (5): 1521–1523. Bibcode:1955PhRv...98.1521H. doi:10.1103/PhysRev.98.1521.
  26. ↑ Hjalmar, E.; Slätis, H.; Thompson, S.G. (1955). "Energy Spectrum of Neutrons from Spontaneous Fission of Californium-252". Physical Review. 100 (5): 1542–1543. Bibcode:1955PhRv..100.1542H. doi:10.1103/PhysRev.100.1542.
  27. 1 2 3 4 Martin, R. C.; Knauer, J. B.; Balo, P. A. (1999). "Production, Distribution, and Applications of Californium-252 Neutron Sources". Applied Radiation and Isotopes. 53 (4–5): 785–92. doi:10.1016/S0969-8043(00)00214-1. PMID   11003521.
  28. 1 2 3 4 Cunningham 1968, p. 103.
  29. 1 2 3 Street, K. Jr.; Thompson, S. G.; Seaborg, Glenn T. (1950). "Chemical Properties of Californium" (PDF). Journal of the American Chemical Society. 72 (10): 4832. doi:10.1021/ja01166a528. hdl:2027/mdp.39015086449173. Archived (PDF) from the original on January 19, 2012. Retrieved February 20, 2011.
  30. ↑ Glenn Theodore Seaborg (1990). Journal of Glenn T. Seaborg, 1946–1958: January 1, 1950 – December 31, 1950. Lawrence Berkeley Laboratory, University of California. p. 80.
  31. ↑ Thompson, S. G.; Street, K. Jr.; A., Ghiorso; Seaborg, Glenn T. (1950). "Element 98". Physical Review. 78 (3): 298. Bibcode:1950PhRv...78..298T. doi: 10.1103/PhysRev.78.298.2 .
  32. ↑ Seaborg 1996, p. 82.
  33. ↑ Weeks & Leichester 1968, p. 849.
  34. 1 2 Weeks & Leichester 1968, p. 848.
  35. ↑ Heiserman 1992, p. 347.
  36. ↑ Diamond, H.; Magnusson, L.; Mech, J.; Stevens, C.; Friedman, A.; Studier, M.; Fields, P.; Huizenga, J. (1954). "Identification of Californium Isotopes 249, 250, 251, and 252 from Pile-Irradiated Plutonium". Physical Review . 94 (4): 1083. Bibcode:1954PhRv...94.1083D. doi:10.1103/PhysRev.94.1083.
  37. ↑ "Element 98 Prepared". Science News Letter. 78 (26). December 1960.
  38. ↑ "The High Flux Isotope Reactor". Oak Ridge National Laboratory. Archived from the original on May 27, 2010. Retrieved August 22, 2010.
  39. ↑ Osborne-Lee 1995, p. 11.
  40. ↑ "Plutonium and Aldermaston – an Historical Account" (PDF). UK Ministry of Defence. September 4, 2001. p. 30. Archived from the original (PDF) on December 13, 2006. Retrieved March 15, 2007.
  41. ↑ Osborne-Lee 1995, p. 6.
  42. 1 2 Haire 2006, p. 1519.
  43. ↑ Haire, R. G.; Baybarz, R. D. (1974). "Crystal Structure and Melting Point of Californium Metal". Journal of Inorganic and Nuclear Chemistry. 36 (6): 1295. doi:10.1016/0022-1902(74)80067-9.
  44. ↑ Zachariasen, W. (1975). "On Californium Metal". Journal of Inorganic and Nuclear Chemistry. 37 (6): 1441–1442. doi:10.1016/0022-1902(75)80787-1.
  45. 1 2 Emsley 2001, p. 90.
  46. 1 2 3 4 5 "Human Health Fact Sheet: Californium" (PDF). Argonne National Laboratory. August 2005. Archived from the original (PDF) on July 21, 2011.
  47. ↑ Fields, P. R.; Studier, M.; Diamond, H.; Mech, J.; Inghram, M.; Pyle, G.; Stevens, C.; Fried, S.; et al. (1956). "Transplutonium Elements in Thermonuclear Test Debris". Physical Review. 102 (1): 180–182. Bibcode:1956PhRv..102..180F. doi:10.1103/PhysRev.102.180.
  48. ↑ Baade, W.; Burbidge, G. R.; Hoyle, F.; Burbidge, E. M.; Christy, R. F.; Fowler, W. A. (August 1956). "Supernovae and Californium 254" (PDF). Publications of the Astronomical Society of the Pacific. 68 (403): 296–300. Bibcode:1956PASP...68..296B. doi: 10.1086/126941 . Archived (PDF) from the original on October 10, 2022. Retrieved September 26, 2012.
  49. ↑ Conway, J. G.; Hulet, E.K.; Morrow, R.J. (February 1, 1962). "Emission Spectrum of Californium". Journal of the Optical Society of America. 52 (2): 222. Bibcode:1962JOSA...52..222C. doi:10.1364/josa.52.000222. OSTI   4806792. PMID   13881026.
  50. ↑ Ruiz-Lapuente1996, p. 274.
  51. ↑ Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements (New ed.). New York, NY: Oxford University Press. ISBN   978-0-19-960563-7.
  52. ↑ Gopka, V. F.; Yushchenko, A. V.; Yushchenko, V. A.; Panov, I. V.; Kim, Ch. (May 15, 2008). "Identification of absorption lines of short half-life actinides in the spectrum of Przybylski's star (HD 101065)". Kinematics and Physics of Celestial Bodies. 24 (2): 89–98. Bibcode:2008KPCB...24...89G. doi:10.3103/S0884591308020049. S2CID   120526363.
  53. 1 2 Krebs 2006, pp. 327–328.
  54. 1 2 Heiserman 1992, p. 348.
  55. ↑ Cunningham 1968, p. 105.
  56. ↑ Haire 2006, p. 1503.
  57. 1 2 NRC 2008, p. 33.
  58. ↑ Seaborg 1994, p. 245.
  59. ↑ Shuler, James (2008). "DOE Certified Radioactive Materials Transportation Packagings" (PDF). United States Department of Energy. p. 1. Archived from the original (PDF) on October 15, 2011. Retrieved April 7, 2011.
  60. ↑ Martin, R. C. (September 24, 2000). Applications and Availability of Californium-252 Neutron Sources for Waste Characterization (PDF). Spectrum 2000 International Conference on Nuclear and Hazardous Waste Management. Chattanooga, Tennessee. Archived from the original (PDF) on June 1, 2010. Retrieved May 2, 2010.
  61. ↑ Seaborg 1990, p. 318.
  62. ↑ Osborne-Lee 1995, p. 33.
  63. ↑ Osborne-Lee 1995, pp. 26–27.
  64. ↑ "Will You be 'Mine'? Physics Key to Detection". Pacific Northwest National Laboratory. October 25, 2000. Archived from the original on February 18, 2007. Retrieved March 21, 2007.
  65. ↑ Davis, S. N.; Thompson, Glenn M.; Bentley, Harold W.; Stiles, Gary (2006). "Ground-Water Tracers – A Short Review". Ground Water. 18 (1): 14–23. doi:10.1111/j.1745-6584.1980.tb03366.x.
  66. 1 2 Osborne-Lee 1995, p. 12.
  67. ↑ Joyce, Malcolm J.; Aspinall, Michael D.; Clark, Mackenzie; Dale, Edward; Nye, Hamish; Parker, Andrew; Snoj, Luka; Spires, Joe (2022). "Wireless information transfer with fast neutrons". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 1021 (1): 165946. Bibcode:2022NIMPA102165946J. doi: 10.1016/j.nima.2021.165946 . ISSN   0168-9002. S2CID   240341300.
  68. ↑ "Evaluation of nuclear criticality safety data and limits for actinides in transport" (PDF). Institut de Radioprotection et de Sûreté Nucléaire. p. 16. Archived from the original (PDF) on May 19, 2011. Retrieved December 20, 2010.
  69. ↑ Mann, Martin (July 1961). "Facts and Fallacies of World War III". Popular Science . 179 (1): 92–95, 178–181. ISSN   0161-7370."force of 10 tons of TNT" on page 180.
  70. ↑ Oganessian, Yu. Ts.; Utyonkov, V.; Lobanov, Yu.; Abdullin, F.; Polyakov, A.; Sagaidak, R.; Shirokovsky, I.; Tsyganov, Yu.; et al. (2006). "Synthesis of the isotopes of elements 118 and 116 in the californium-249 and 245Cm+48Ca fusion reactions". Physical Review C. 74 (4): 044602–044611. Bibcode:2006PhRvC..74d4602O. doi: 10.1103/PhysRevC.74.044602 .
  71. ↑ Sanderson, K. (October 17, 2006). "Heaviest element made – again". Nature News. Nature. doi:10.1038/news061016-4. S2CID   121148847.
  72. ↑ Schewe, P.; Stein, B. (October 17, 2006). "Elements 116 and 118 Are Discovered". Physics News Update. American Institute of Physics. Archived from the original on October 26, 2006. Retrieved October 19, 2006.
  73. ↑ <Please add first missing authors to populate metadata.> (April 1961). "Element 103 Synthesized". Science News-Letter. 79 (17): 259. doi:10.2307/3943043. JSTOR   3943043.
  74. ↑ Cunningham 1968, p. 106.

Bibliography

Commons-logo.svg Media related to Californium at Wikimedia Commons

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.