関: actinide、actinoid series element

WordNet

any of a series of radioactive elements with atomic numbers 89 through 103 (同)actinide, actinon
having a radial form; "starfish are actinoid--that is, they are radially symmetrical"

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/01/02 21:53:46」(JST)

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Actinides in the periodic table

The atomic bomb dropped on Nagasaki had a plutonium charge.^[1]

The actinide or actinoid (IUPAC nomenclature) series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.^[2]^[3]^[4]^[5]

The actinide series derives its name from the group 3 element actinium. All but one of the actinides are f-block elements, corresponding to the filling of the 5f electron shell; lawrencium, a d-block element, is also generally considered an actinide. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence.

89
Ac

90
Th

91
Pa

92
U

93
Np

94
Pu

95
Am

96
Cm

97
Bk

98
Cf

99
Es

100
Fm

101
Md

102
No

103
Lr

Of the actinides, primordial thorium and uranium occur naturally in substantial quantities and small amounts of persisting natural plutonium have also been identified. The radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium, americium, curium, berkelium and californium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements.^[2]^[6] Nuclear weapons tests have released at least six actinides heavier than plutonium into the environment; analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium, curium, berkelium, californium, einsteinium and fermium.^[7]

All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.

In presentations of the periodic table, the lanthanides and the actinides are customarily shown as two additional rows below the main body of the table,^[2] with placeholders or else a selected single element of each series (either lanthanum or lutetium, and either actinium or lawrencium, respectively) shown in a single cell of the main table, between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods).

1 Discovery, isolation and synthesis
- 1.1 From actinium to neptunium
- 1.2 Plutonium and above
2 Isotopes
3 Distribution in nature
4 Extraction
5 Properties
- 5.1 Physical properties
- 5.2 Chemical properties
6 Compounds
- 6.1 Oxides and hydroxides
- 6.2 Salts
7 Applications
8 Toxicity
9 See also
10 References and notes
11 Bibliography
12 External links

Discovery, isolation and synthesis

Synthesis of transuranium elements^[8]^[9]
Element	Year	Method
Neptunium	1940	Bombarding ²³⁸U by neutrons
Plutonium	1941	Bombarding ²³⁸U by deuterons
Americium	1944	Bombarding ²³⁹Pu by neutrons
Curium	1944	Bombarding ²³⁹Pu by α-particles
Berkelium	1949	Bombarding ²⁴¹Am by α-particles
Californium	1950	Bombarding ²⁴²Cm by α-particles
Einsteinium	1952	As a product of nuclear explosion
Fermium	1952	As a product of nuclear explosion
Mendelevium	1955	Bombarding ²⁵³Es by α-particles
Nobelium	1965	Bombarding ²⁴³Am by ¹⁵N or ²³⁸U with α-particles
Lawrencium	1961–1971	Bombarding ²⁵²Cf by ¹⁰B or ¹¹B and of ²⁴³Am with ¹⁸O

Like the lanthanides, the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups: transuranium elements, which follow uranium in the periodic table—and transplutonium elements, which follow plutonium. Compared to the lanthanides, which (except for promethium) are found in nature in appreciable quantities, most actinides are rare. The most abundant, or easy to synthesize actinides are uranium and thorium, followed by plutonium, americium, actinium, protactinium and neptunium.^[10]

The existence of transuranium elements was suggested by Enrico Fermi based on his experiments in 1934.^[11]^[12] However, even though four actinides were known by that time, it was not yet understood that they formed a family similar to lanthanides. The prevailing view that dominated early research into transuranics was that they were regular elements in the 7th period, with thorium, protactinium and uranium corresponding to 6th-period hafnium, tantalum and tungsten, respectively. Synthesis of transuranics gradually undermined this point of view. By 1944 an observation that curium failed to exhibit oxidation states above 4 (whereas its supposed 6th period neighbor, platinum, can reach oxidation state of 7) prompted Glenn Seaborg to formulate a so-called "actinide hypothesis". Studies of known actinides and discoveries of further transuranic elements provided more data in support of this point of view, but the phrase "actinide hypothesis" (the implication being that "hypothesis" is something that has not been decisively proven) remained in active use by scientists through the late 1950s.^[13]^[14]

At present, there are two major methods of producing isotopes of transplutonium elements: irradiation of the lighter elements with either neutrons or accelerated charged particles. The first method is most important for applications, as only neutron irradiation using nuclear reactors allows the production of sizeable amounts of synthetic actinides; however, it is limited to relatively light elements. The advantage of the second method is that elements heavier than plutonium, as well as neutron-deficient isotopes, can be obtained, which are not formed during neutron irradiation.^[15]

In 1962–1966, there were attempts in the United States to produce transplutonium isotopes using a series of six underground nuclear explosions. Small samples of rock were extracted from the blast area immediately after the test to study the explosion products, but no isotopes with mass number greater than 257 could be detected, despite predictions that such isotopes would have relatively long half-lives of α-decay. This inobservation was attributed to spontaneous fission owing to the large speed of the products and to other decay channels, such as neutron emission and nuclear fission.^[16]

From actinium to neptunium

Enrico Fermi suggested the existence of transuranium elements in 1934.

Uranium and thorium were the first actinides discovered. Uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore. He named it after the planet Uranus,^[6] which had been discovered only eight years earlier. Klaproth was able to precipitate a yellow compound (likely sodium diuranate) by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide. He then reduced the obtained yellow powder with charcoal, and extracted a black substance that he mistook for metal.^[17] Only 60 years later, the French scientist Eugène-Melchior Péligot identified it with uranium oxide. He also isolated the first sample of uranium metal by heating uranium tetrachloride with potassium.^[18] The atomic mass of uranium was then calculated as 120, but Dmitri Mendeleev in 1872 corrected it to 240 using his periodicity laws. This value was confirmed experimentally in 1882 by K. Zimmerman.^[19]^[20]

Thorium oxide was discovered by Friedrich Wöhler in the mineral, which was found in Norway (1827).^[21] Jöns Jacob Berzelius characterized this material in more detail by in 1828. By reduction of thorium tetrachloride with potassium, he isolated the metal and named it thorium after the Norse god of thunder and lightning Thor.^[22]^[23] The same isolation method was later used by Péligot for uranium.^[6]

Actinium was discovered in 1899 by André-Louis Debierne, an assistant of Marie Curie, in the pitchblende waste left after removal of radium and polonium. He described the substance (in 1899) as similar to titanium^[24] and (in 1900) as similar to thorium.^[25] The discovery of actinium by Debierne was however questioned in 1971^[26] and 2000,^[27] arguing that Debierne's publications in 1904 contradicted his earlier work of 1899–1900. The name for word actinium comes from the Greek aktis, aktinos (ακτίς, ακτίνος), meaning beam or ray. This metal was discovered not by its own radiation but by the radiation of the daughter products.^[28]^[29] Owing to the close similarity of actinium and lanthanum and low abundance, pure actinium could only be produced in 1950. The term actinide was probably introduced by Victor Goldschmidt in 1937.^[30]^[31]

Protactinium was possibly isolated in 1900 by William Crookes.^[32] It was first identified in 1913, when Kasimir Fajans and Oswald Helmuth Göhring encountered the short-lived isotope ^234mPa (half-life 1.17 minutes) during their studies of the ²³⁸U decay. They named the new element brevium (from Latin brevis meaning brief);^[33]^[34] the name was changed to protoactinium (from Greek πρῶτος + ἀκτίς meaning "first beam element") in 1918 when two groups of scientists, led by Otto Hahn and Lise Meitner of Germany and Frederick Soddy and John Cranston of Great Britain, independently discovered ²³¹Pa. The name was shortened to Protactinium in 1949. This element was little characterized until 1960, when A. G. Maddock and co-workers in UK produced 130 grams of protactinium from 60 tonnes of waste left after extraction of uranium from its ore.^[35]

Neptunium (named for the planet Neptune, the next planet out from Uranus, after which uranium was named) was discovered by Edwin McMillan and Philip H. Abelson in 1940 in Berkeley, California.^[36] They produced the ²³⁹Np isotope (half-life 2.4 days) by bombarding uranium with slow neutrons.^[35] It was the first transuranium element produced synthetically.^[37]

Plutonium and above

Glenn T. Seaborg and his group at the University of California at Berkeley synthesized Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No and element 106, which was later named seaborgium in his honor while he was still living. They also synthesized more than 100 atomic actinide isotopes.

Transuranium elements do not occur in sizeable quantities in nature and are commonly synthesized via nuclear reactions conducted with nuclear reactors. For example, under irradiation with reactor neutrons, uranium-238 partially converts to plutonium-239:

In this way, Enrico Fermi with collaborators, using the first nuclear reactor Chicago Pile-1, obtained significant amounts of plutonium-239, which were then used in nuclear weapons.^[38]

Actinides with the highest mass numbers are synthesized by bombarding uranium, plutonium, curium and californium with ions of nitrogen, oxygen, carbon, neon or boron in a particle accelerator. So, nobelium was produced by bombarding uranium-238 with neon-22 as

.

First isotopes of transplutonium elements, americium-241 and curium-242, were synthesized in 1944 by Glenn T. Seaborg, Ralph A. James and Albert Ghiorso.^[39] Curium-242 was obtained by bombarding plutonium-239 with 32-MeV α-particles

.

The americium-241 and curium-242 isotopes also were produced by irradiating plutonium in a nuclear reactor. The latter element was named after Marie Curie and her husband Pierre who are noted for discovering radium and for their work in radioactivity.^[40]

Bombarding curium-242 with α-particles resulted in an isotope of californium ²⁴⁵Cf (1950), and a similar procedure yielded in 1949 berkelium-243 from americium-241.^[41] The new elements were named after Berkeley, California, by analogy with its lanthanide homologue terbium, which was named after the village of Ytterby in Sweden.^[42]

In 1945, B. B. Cunningham obtained the first bulk chemical compound of a transplutonium element, namely americium hydroxide.^[43] Over the next three to four years, milligram quantities of americium and microgram amounts of curium were accumulated that allowed production of isotopes of berkelium (Thomson, 1949)^[44]^[45] and californium (Thomson, 1950).^[46]^[47]^[48] Sizeable amounts of these elements were produced only in 1958 (Burris B. Cunningham and Stanley G. Thomson),^[49] and the first californium compound (0.3 µg of CfOCl) was obtained only in 1960 by B. B. Cunningham and J. C. Wallmann).^[50]

Einsteinium and fermium were identified in 1952–1953 in the fallout from the "Ivy Mike" nuclear test (1 November 1952), the first successful test of a hydrogen bomb. Instantaneous exposure of uranium-238 to a large neutron flux resulting from the explosion produced heavy isotopes of uranium, including uranium-253 and uranium-255, and their β-decay yielded einsteinium-253 and fermium-255. The discovery of the new elements and the new data on neutron capture were initially kept secret on the orders of the U.S. military until 1955 due to Cold War tensions.^[51]^[52] Nevertheless, the Berkeley team were able to prepare einsteinium and fermium by civilian means, through the neutron bombardment of plutonium-239, and published this work in 1954 with the disclaimer that it was not the first studies that had been carried out on the elements.^[53]^[54] The "Ivy Mike" studies were declassified and published in 1955.^[51] The first significant (submicrograms) amounts of einsteinium were produced in 1961 by Cunningham and colleagues, but this has not been done for fermium yet.^[55]

The first isotope of mendelevium, ²⁵⁶Md (half-life 87 min), was synthesized by Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey and Stanley G. Thompson when they bombarded an ²⁵³Es target with alpha particles in the 60-inch cyclotron of Berkeley Radiation Laboratory; this was the first isotope of any element to be synthesized one atom at a time.^[56]

There were several attempts to obtain isotopes of nobelium by Swedish (1957) and American (1958) groups, but the first reliable results was the synthesis of ²⁵⁶No by the Russian group (Georgy Flyorov et al.) in 1965, as acknowledges by the IUPAC in 1992. In their experiments, Flyorov et al. bombarded uranium-238 with neon-22.^[8]

In 1961, Ghiorso et al. obtained the first isotope of lawrencium by irradiating californium (mostly californium-252) with boron-10 and boron-11 ions.^[8] The mass number of this isotope was not clearly established (possibly 258 or 259) at the time. In 1965, ²⁵⁶Lr were synthesized by Flyorov et al. from ²⁴³Am and ¹⁸O. Thus IUPAC recognized the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium.

Isotopes

Nuclear properties of isotopes of the most important transplutonium isotopes^[57]^[58]^[59]
Isotope	Half-life	Probability of spontaneous fission in %	Emission energy, MeV (yield in %)		Specific activity^[60] of
Isotope	Half-life	Probability of spontaneous fission in %	α	γ	α, β-particles, Bq/kg	fission, Bq/kg
²⁴¹Am	432.2(7) years	4.3(18)×10⁻¹⁰	5.485 (84.8) 5.442 (13.1) 5.388 (1.66)	0.059 (35.9) 0.026 (2.27)	1.27×10¹⁴	546.1
²⁴³Am	7.37(4)×10³ years	3.7(2)×10⁻⁹	5.275 (87.1) 5.233 (11.2) 5.181 (1.36)	0.074 (67.2) 0.043 (5.9)	7.39×10¹²	273.3
²⁴²Cm	162.8(2) days	6.2(3)×10⁻⁶	6.069 (25.92) 6.112 (74.08)	0.044 (0.04) 0.102 (4×10⁻³)	1.23×10¹⁷	7.6×10⁹
²⁴⁴Cm	18.10(2) years	1.37(3)×10⁻⁴	5.762 (23.6) 5.804 (76.4)	0.043 (0.02) 0.100 (1.5×10⁻³)	2.96×10¹⁵	4.1×10⁹
²⁴⁵Cm	8.5(1)×10³ years	6.1(9)×10⁻⁷	5.529 (0.58) 5.488 (0.83) 5.361 (93.2)	0.175 (9.88) 0.133 (2.83)	6.35×10¹²	3.9×10⁴
²⁴⁶Cm	4.76(4)×10³ years	0.02615(7)	5.343 (17.8) 5.386 (82.2)	0.045 (19)	1.13×10¹³	2.95×10⁹
²⁴⁷Cm	1.56(5)×10⁷ years	—	5.267 (13.8) 5.212 (5.7) 5.147 (1.2)	0.402 (72) 0.278 (3.4)	3.43×10⁹	—
²⁴⁸Cm	3.48(6)×10⁵ years	8.39(16)	5.034 (16.52) 5.078 (75)	—	1.40×10¹¹	1.29×10¹⁰
²⁴⁹Bk	330(4) days	4.7(2)×10⁻⁸	5.406 (1×10⁻³) 5.378 (2.6×10⁻⁴)	0.32 (5.8×10⁻⁵)	5.88×10¹⁶	2.76×10⁷
²⁴⁹Cf	351(2) years	5.0(4)×10⁻⁷	6.193 (2.46) 6.139 (1.33) 5.946 (3.33)	0.388 (66) 0.333 (14.6)	1.51×10¹⁴	7.57×10⁵
²⁵⁰Cf	13.08(9) years	0.077(3)	5.988 (14.99) 6.030 (84.6)	0.043	4.04×10¹⁵	3.11×10¹²
²⁵¹Cf	900(40) years	?	6.078 (2.6) 5.567 (0.9) 5.569 (0.9)	0.177 (17.3) 0.227 (6.8)	5.86×10¹³	—
²⁵²Cf	2.645(8) years	3.092(8)	6.075 (15.2) 6.118 (81.6)	0.042 (1.4×10⁻²) 0.100 (1.3×10⁻²)	1.92×10¹⁶	6.14×10¹⁴
²⁵⁴Cf	60.5(2) days	≈100	5.834 (0.26) 5.792 (5.3×10⁻²)	—	9.75×10¹⁴	3.13×10¹⁷
²⁵³Es	20.47(3) days	8.7(3)×10⁻⁶	6.540 (0.85) 6.552 (0.71) 6.590 (6.6)	0.387 (0.05) 0.429 (8×10⁻³)	9.33×10¹⁷	8.12×10¹⁰
²⁵⁴Es	275.7(5) days	< 3×10⁻⁶	6.347 (0.75) 6.358 (2.6) 6.415 (1.8)	0.042 (100) 0.034 (30)	6.9×10¹⁶	—
²⁵⁵Es	39.8(12) days	0.0041(2)	6.267 (0.78) 6.401 (7)	—	4.38×10¹⁷(β) 3.81×10¹⁶(α)	1.95×10¹³
²⁵⁵Fm	20.07(7) hours	2.4(10)×10⁻⁵	7.022 (93.4) 6.963 (5.04) 6.892 (0.62)	0.00057 (19.1) 0.081 (1)	2.27×10¹⁹	5.44×10¹²
²⁵⁶Fm	157.6(13) min	91.9(3)	6.872 (1.2) 6.917 (6.9)	—	1.58×10²⁰	1.4×10¹⁹
²⁵⁷Fm	100.5(2) days	0.210(4)	6.752 (0.58) 6.695 (3.39) 6.622 (0.6)	0.241 (11) 0.179 (8.7)	1.87×10¹⁷	3.93×10¹⁴
²⁵⁶Md	77(2) min	—	7.142 (1.84) 7.206 (5.9)	—	3.53×10²⁰	—
²⁵⁷Md	5.52(5) hours	—	7.074 (14)	0.371 (11.7) 0.325 (2.5)	8.17×10¹⁹	—
²⁵⁸Md	51.5(3) days	—	6.73	—	3.64×10¹⁷	—
²⁵⁵No	3.1(2) min	—	8.312 (1.16) 8.266 (2.6) 8.121 (27.8)	0.187 (3.4)	8.78×10²¹	—
²⁵⁹No	58(5) min	—	7.455 (9.8) 7.500 (29.3) 7.533 (17.3)	—	4.63×10²⁰	—
²⁵⁶Lr	27(3) s	< 0.03	8.319 (5.4) 8.390 (16) 8.430 (33)	—	5.96×10²²	—
²⁵⁷Lr	646(25) ms	—	8.796 (18) 8.861 (82)	—	1.54×10²⁴	—

Actinides have 89 to 103 protons and usually have 117 to 159 neutrons.

Thirty-one isotopes of actinium and eight excited isomeric states of some of its nuclides were identified by 2010.^[57] Three isotopes, ²²⁵Ac, ²²⁷Ac and ²²⁸Ac, were found in nature and the others were produced in the laboratory; only the three natural isotopes are used in applications. Actinium-225 is a member of radioactive neptunium series;^[61] it was first discovered in 1947 as a fission product of uranium-233, it is an α-emitter with a half-life of 10 days. Actinium-225 is less available than actinium-228, but is more promising in radiotracer applications.^[29] Actinium-227 (half-life 21.77 years) occurs in all uranium ores, but in small quantities. One gram of uranium (in radioactive equilibrium) contains only 2×10⁻¹⁰ gram of ²²⁷Ac.^[29]^[57] Actinium-228 is a member of radioactive thorium series formed by the decay of ²²⁸Ra;^[61] it is a β^– emitter with a half-life of 6.15 hours. In one tonne of thorium there is 5×10⁻⁸ gram of ²²⁸Ac. It was discovered by Otto Hahn in 1906.^[29]

Twenty nine isotopes of protactinium are known with mass numbers 212–240^[57] as well as three excited isomeric states. Only ²³¹Pa and ²³⁴Pa have been found in nature. All the isotopes have short lifetime, except for protactinium-231 (half-life 32,760 years). The most important isotopes are ²³¹Pa and ²³³Pa, which is an intermediate product in obtaining uranium-233 and is the most affordable among artificial isotopes of protactinium. ²³³Pa has convenient half-life and energy of γ-radiation, and thus was used in most studies of protactinium chemistry. Protactinium-233 is a β-emitter with a half-life of 26.97 days.^[57]^[62]

Uranium has the highest number (25) of both natural and synthetic isotopes. They have mass numbers of 217–242,^[58] and three of them, ²³⁴U, ²³⁵U and ²³⁸U, are present in appreciable quantities in nature. Among others, the most important is ²³³U, which is a final product of transformations of ²³²Th irradiated by slow neutrons. ²³³U has a very higher fission efficiency by low-energy (thermal) neutrons, compared e.g. with ²³⁵U. Most uranium chemistry studies were carried out on uranium-238 owing to its long half-life of 4.4×10⁹ years.^[63]

There are 19 isotopes of neptunium with mass numbers from 225 to 244;^[58] they are all highly radioactive. The most popular among scientists are long-lived ²³⁷Np (t_½ = 2.20×10⁶ years) and short-lived ²³⁹Np, ²³⁸Np (t_½ ~ 2 days).^[37]

Sixteen isotopes of americium are known with mass numbers from 232 to 248.^[58] The most important are ²⁴¹Am and ²⁴³Am, which are alpha-emitters and also emit soft, but intense γ-rays; both of them can be obtained in an isotopically pure form. Chemical properties of americium were first studied with ²⁴¹Am, but later shifted to ²⁴³Am, which is almost 20 times less radioactive. The disadvantage of ²⁴³Am is production of the short-lived daughter isotope ²³⁹Np, which has to be considered in the data analysis.^[64]

Among 19 isotopes of curium,^[58] the most accessible are ²⁴²Cm and ²⁴⁴Cm; they are α-emitters, but with much shorter lifetime than the americium isotopes. These isotopes emit almost no γ-radiation, but undergo spontaneous fission with the associated emission of neutrons. More long-lived isotopes of curium (^245–248Cm, all α-emitters) are formed as a mixture during neutron irradiation of plutonium or americium. Upon short irradiation, this mixture is dominated by curium-246, and then curium-248 begins to accumulate. Both of these isotopes, especially ²⁴⁸Cm, have a longer half-life (3.48×10⁵ years) and are much more convenient for carrying out chemical research than ²⁴²Cm and ²⁴⁴Cm, but they also have a rather high rate of spontaneous fission. ²⁴⁷Cm has the longest lifetime among isotopes of curium (1.56×10⁷ years), but is not formed in large quantities because of the strong fission induced by thermal neutrons.

Fourteen isotopes of berkelium were identified with mass numbers 238–252.^[58] Only ²⁴⁹Bk is available in large quantities; it has a relatively short half-life of 330 days and emits mostly soft β-particles, which are inconvenient for detection. Its alpha radiation is rather weak (1.45×10⁻³% with respect to β-radiation), but is sometimes used to detect this isotope. ²⁴⁷Bk is an alpha-emitter with a long half-life of 1,380 years, but it is hard to obtain in appreciable quantities; it is not formed upon neutron irradiation of plutonium because of the β-stability of isotopes of curium isotopes with mass number below 248.^[64]

Isotopes of californium with mass numbers 237–256 are formed in nuclear reactors;^[58] californium-253 is a β-emitter and the rest are α-emitters. The isotopes with even mass numbers (²⁵⁰Cf, ²⁵²Cf and ²⁵⁴Cf) have a high rate of spontaneous fission, especially ²⁵⁴Cf of which 99.7% decays by spontaneous fission. Californium-249 has a relatively long half-life (352 years), weak spontaneous fission and strong γ-emission that facilitates its identification. ²⁴⁹Cf is not formed in large quantities in a nuclear reactor because of the slow β-decay of the parent isotope ²⁴⁹Bk and a large cross section of interaction with neutrons, but it can be accumulated in the isotopically pure form as the β-decay product of (pre-selected) ²⁴⁹Bk. Californium produced by reactor-irradiation of plutonium mostly consists of ²⁵⁰Cf and ²⁵²Cf, the latter being predominant for large neutron fluences, and its study is hindered by the strong neutron radiation.^[65]

Properties of some transplutonium isotope pairs^[66]
Parent isotope	t_½	Daughter isotope	t_½	Time to establish radioactive equilibrium
²⁴³Am	7370 years	²³⁹Np	2.35 days	47.3 days
²⁴⁵Cm	8265 years	²⁴¹Pu	14 years	129 years
²⁴⁷Cm	1.64×10⁷ years	²⁴³Pu	4.95 hours	7.2 days
²⁵⁴Es	270 days	²⁵⁰Bk	3.2 hours	35.2 hours
²⁵⁵Es	39.8 days	²⁵⁵Fm	22 hours	5 days
²⁵⁷Fm	79 days	²⁵³Cf	17.6 days	49 days

Among the 16 known isotopes of einsteinium with mass numbers from 241 to 257^[58] the most affordable is ²⁵³Es. It is an α-emitter with a half-life of 20.47 days, a relatively weak γ-emission and small spontaneous fission rate as compared with the isotopes of californium. Prolonged neutron irradiation also produces a long-lived isotope ²⁵⁴Es (t_½ = 275.5 days).^[65]

Nineteen isotopes of fermium are known with mass numbers of 242–260. ²⁵⁴Fm, ²⁵⁵Fm and ²⁵⁶Fm are α-emitters with a short half-life (hours), which can be isolated in significant amounts. ²⁵⁷Fm (t_½ = 100 days) can accumulate upon prolonged and strong irradiation. All these isotopes are characterized by high rates of spontaneous fission.^[65]^[67]

Among the 15 known isotopes of mendelevium (mass numbers from 245 to 260),^[58] the most studied is ²⁵⁶Md, which mainly decays through the electron capture (α-radiation is ≈10%) with the half-life of 77 minutes. Another alpha emitter, ²⁵⁸Md, has a half-life of 53 days. Both these isotopes are produced from rare einsteinium (²⁵³Es and ²⁵⁵Es respectively), that limits their so their availability.^[57]

Long-lived isotopes of nobelium and isotopes of lawrencium (and of heavier elements) have relatively small half-lives. For nobelium 11 isotopes are known with mass numbers 250–260 and 262. Chemical properties of nobelium and lawrencium were studied with ²⁵⁵No (t_½ = 3 min) and ²⁵⁶Lr (t_½ = 35 s). The longest-lived nobelium isotope ²⁵⁹No has a half-life of 1.5 hours.^[57]

Distribution in nature

Unprocessed uranium ore

Thorium and uranium are the most abundant actinides in nature with the respective mass concentrations of 1.6×10⁻³% and 4×10⁻⁴%.^[68] Uranium mostly occurs in the Earth's crust as a mixture of its oxides in the minerals uraninite, which is also called pitchblende because of its black color. There are several dozens of other uranium minerals such as carnotite (KUO₂VO₄·3H₂O) and autunite (Ca(UO₂)₂(PO₄)₂·nH₂O). The isotopic composition of natural uranium is ²³⁸U (relative abundance 99.2742%), ²³⁵U (0.7204%) and ²³⁴U (0.0054%); of these ²³⁸U has the largest half-life of 4.51×10⁹ years.^[69]^[70] The worldwide production of uranium in 2009 amounted to 50,572 tonnes, of which 27.3% was mined in Kazakhstan. Other important uranium mining countries are Canada (20.1%), Australia (15.7%), Namibia (9.1%), Russia (7.0%), and Niger (6.4%).^[71]

Content of plutonium in uranium and thorium ores^[72]
Ore	Location	Uranium content, %	Mass ratio ²³⁹Pu/ore	Ratio ²³⁹Pu/U (×10¹²)
Uraninite	Canada	13.5	9.1×10⁻¹²	7.1
Uraninite	Congo	38	4.8×10⁻¹²	12
Uraninite	Colorado, US	50	3.8×10⁻¹²	7.7
Monazite	Brazil	0.24	2.1×10⁻¹⁴	8.3
Monazite	North Carolina, US	1.64	5.9×10⁻¹⁴	3.6
Fergusonite	-	0.25	<1×10⁻¹⁴	<4
Carnotite	-	10	<4×10⁻¹⁴	<0.4

The most abundant thorium minerals are thorianite (ThO₂), thorite (ThSiO₄) and monazite, ((Th,Ca,Ce)PO₄). Most thorium minerals contain uranium and vice versa; and they all have significant fraction of lanthanides. Rich deposits of thorium minerals are located in the United States (440,000 tonnes), Australia and India (~300,000 tonnes each) and Canada (~100,000 tonnes).^[73]

The abundance of actinium in the Earth's crust is only about 5×10⁻¹⁵%.^[62] Actinium is mostly present in uranium-containing, but also in other minerals, though in much smaller quantities. The content of actinium in most natural objects corresponds to the isotopic equilibrium of parent isotope ²³⁵U, and it is not affected by the weak Ac migration.^[29] Protactinium is more abundant (10⁻¹²%) in the Earth's crust than actinium. It was discovered in the uranium ore in 1913 by Fajans and Göhring.^[33] As actinium, the distribution of protactinium follows that of ²³⁵U.^[62]

The half-life of the longest-lived isotope of neptunium, ²³⁷Np, is negligible compared to the age of the Earth. Thus neptunium is present in nature in negligible amounts produced as intermediate decay products of other isotopes.^[37] Traces of plutonium in uranium minerals were first found in 1942, and the more systematic results on ²³⁹Pu are summarized in the table (no other plutonium isotopes could be detected in those samples). The upper limit of abundance of the longest-living isotope of plutonium, ²⁴⁴Pu, is 3×10⁻²⁰%. Plutonium could not be detected in samples of lunar soil. Owing to its scarcity in nature, most plutonium is produced synthetically.^[72]

Negligible amounts of americium, curium, berkelium and californium are produced by neutron capture reactions and beta decay in very highly concentrated uranium-bearing deposits.^[74]

Extraction

Monazite—a major thorium mineral

Owing to the low abundance of actinides, their extraction is a complex, multistep process. Fluorides of actinides are usually used because they are insoluble in water and can be easily separated with redox reactions. Fluorides are reduced with calcium, magnesium or barium:^[75]

Among the actinides, thorium and uranium are the easiest to isolate. Thorium is extracted mostly from monazite: thorium diphosphate (Th(PO₄)₂) is reacted with nitric acid, and the produced thorium nitrate treated with tributyl phosphate. Rare-earth impurities are separated by increasing the pH in sulfate solution.^[75]

In another extraction method, monazite is decomposed with a 45% aqueous solution of sodium hydroxide at 140 °C. Mixed metal hydroxides are extracted first, filtered at 80 °C, washed with water and dissolved with concentrated hydrochloric acid. Next, the acidic solution is neutralized with hydroxides to pH = 5.8 that results in precipitation of thorium hydroxide (Th(OH)₄) contaminated with ~3% of rare-earth hydroxides; the rest of rare-earth hydroxides remains in solution. Thorium hydroxide is dissolved in an inorganic acid and then purified from the rare earth elements. An efficient method is the dissolution of thorium hydroxide in nitric acid, because the resulting solution can be purified by extraction with organic solvents:^[75]

Separation of uranium and plutonium from nuclear fuel^[76]

Th(OH)₄ + 4 HNO₃ → Th(NO₃)₄ + 4 H₂O

Metallic thorium is separated from the anhydrous oxide, chloride or fluoride by reacting it with calcium in an inert atmosphere:^[77]

ThO₂ + 2 Ca → 2 CaO + Th

Sometimes thorium is extracted by electrolysis of a fluoride in a mixture of sodium and potassium chloride at 700–800 °C in a graphite crucible. Highly pure thorium can be extracted from its iodide with the crystal bar process.^[78]

Uranium is extracted from its ores in various ways. In one method, the ore is burned and then reacted with nitric acid to convert uranium into a dissolved state. Treating the solution with a solution of tributyl phosphate (TBP) in kerosene transforms uranium into an organic form UO₂(NO₃)₂(TBP)₂. The insoluble impurities are filtered and the uranium is extracted by reaction with hydroxides as (NH₄)₂U₂O₇ or with hydrogen peroxide as UO₄·2H₂O.^[75]

When the uranium ore is rich in such minerals as dolomite, magnesite, etc., those minerals consume much acid. In this case, the carbonate method is used for uranium extraction. Its main component is an aqueous solution of sodium carbonate, which converts uranium into a complex [UO₂(CO₃)₃]^4–, which is stable in aqueous solutions at low concentrations of hydroxide ions. The advantages of the sodium carbonate method are that the chemicals have low corrosivity (compared to nitrates) and that most non-uranium metals precipitate from the solution. The disadvantage is that tetravalent uranium compounds precipitate as well. Therefore, the uranium ore is treated with sodium carbonate at elevated temperature and under oxygen pressure:

2 UO₂ + O₂ + 6 CO2−
3 → 2 [UO₂(CO₃)₃]^4–

This equation suggests that the best solvent for the uranium carbonate processing is a mixture of carbonate with bicarbonate. At high pH, this results in precipitation of diuranate, which is treated with hydrogen in the presence of nickel yielding an insoluble uranium tetracarbonate.^[75]

Another separation method uses polymeric resins as a polyelectrolyte. Ion exchange processes in the resins result in separation of uranium. Uranium from resins is washed with a solution of ammonium nitrate or nitric acid that yields uranyl nitrate, UO₂(NO₃)₂·6H₂O. When heated, it turns into UO₃, which is converted to UO₂ with hydrogen:

UO₃ + H₂ → UO₂ + H₂O

Reacting uranium dioxide with fluoric acid changes it to uranium tetrafluoride, which yields uranium metal upon reaction with magnesium metal:^[77]

4 HF + UO₂ → UF₄ + 2 H₂O

To extract plutonium, neutron-irradiated uranium is dissolved in nitric acid, and a reducing agent (FeSO₄, or H₂O₂) is added to the resulting solution. This addition changes the oxidation state of plutonium from +6 to +4, while uranium remains in the form of uranyl nitrate (UO₂(NO₃)₂). The solution is treated with a reducing agent and neutralized with ammonium carbonate to pH = 8 that results in precipitation of Pu⁴⁺ compounds.^[75]

In another method, Pu⁴⁺and UO2+
2 are first extracted with tributyl phosphate, then reacted with hydrazine washing out the recovered plutonium.^[75]

The major difficulty in separation of actinium is the similarity of its properties with those of lanthanum. Thus actinium is either synthesized in nuclear reactions from isotopes of radium or separated using ion-exchange procedures.^[29]

Properties

Actinides have similar properties to lanthanides. The 6d and 7s electronic shells are filled in actinium and thorium, and the 5f shell is being filled with further increase in atomic number; the 4f shell is filled in the lanthanides. The first experimental evidence for the filling of the 5f shell in actinides was obtained by McMillan and Abelson in 1940.^[79] As in lanthanides (see lanthanide contraction), the ionic radius of actinides monotonically decreases with atomic number (see also Aufbau principle).^[80]

Properties of actinides (the mass of the most long-lived isotope is in square brackets)^[70]^[81]
Property	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr
Core charge	89	90	91	92	93	94	95	96	97	98	99	100	101	102	103
atomic mass	[227]	232.0381	231.03588	238.02891	[237]	[244]	[243]	[247]	[247]	[251]	[252]	[257]	[258]	[259]	[262]
Number of natural isotopes^[74]	3	9	5	9	4	5	5	8	2	5	—	—	—	—	—
Natural isotopes^[74]^[82]	225, 227–228	226–232, 234–235	231, 233–236	232–240	237–240	238–240, 242, 244	241–245	242–249	249–250	249–253	—	—	—	—	—
Longest-lived isotope	227	232	231	238	237	244	243	247	247	251	252	257	258	259	262
Half-life of the longest-lived isotope	21.8 years	14 billion years	32,500 years	4.47 billion years	2.14 million years	80.8 million years	7,370 years	15.6 million years	1,400 years	900 years	1.29 years	100.5 days	52 days	58 min	261 min
Electronic configuration in the ground state	6d¹7s²	6d²7s²	5f²6d¹7s²or 5f¹6d²7s²	5f³6d¹7s²	5f⁴6d¹7s²or 5f⁵7s²	5f⁶7s²	5f⁷7s²	5f⁷6d¹7s²	5f⁹7s²or 5f⁸6d¹7s²	5f¹⁰7s²	5f¹¹7s²	5f¹²7s²	5f¹³7s²	5f¹⁴7s²	5f¹⁴7s²7p¹
Oxidation state	3	3, 4	3, 4, 5	3, 4, 5, 6	3, 4, 5, 6, 7	3, 4, 5, 6, 7	2, 3, 4	3, 4	3, 4	2, 3	2, 3	2, 3	2, 3	2, 3	3
Metallic radius, nm	0.203	0.180	0.162	0.153	0.150	0.162	0.173	0.174	0.170	0.186	0.186	—	—	—	—
Ionic radius, nm: An⁴⁺ An³⁺	— 0.126	0.114 —	0.104 0.118	0.103 0.118	0.101 0.116	0.100 0.115	0.099 0.114	0.099 0.112	0.097 0.110	0.096 0.109	0.085 0.098	0.084 0.091	0.084 0.090	0.084 0.095	0.083 0.088
Temperature, °C: melting boiling	1050 3300	1750 4800	1572 4400	1130 3800	640 3900	640 3230	1176 2610	1340 —	1050 —	900 —	860 —	1530 —	830 —	830 —	1630 —
Density, g/cm³	10.07	11.78	15.37	19.06	20.25	19.84	11.7	13.51	14.78	15.1	8.84
Standard electrode potential, V: E° (An⁴⁺/An⁰) E° (An³⁺/An⁰)	— −2.13	−1.83 —	−1.47 —	−1.38 −1.66	−1.30 −1.79	−1.25 −2.00	−0.90 −2.07	−0.75 −2.06	−0.55 −1.96	−0.59 −1.97	−0.36 −1.98	−0.29 −1.96	— −1.74	— −1.20	- −2.10
Color [M(H₂O)_n]⁴⁺ [M(H₂O)_n]³⁺	— Colorless	Colorless Blue	Yellow Dark blue	Green Purple	Yellow-green Purple	Brown Violet	Red Rose	Yellow Colorless	Beige Yellow-green	Green Green	— Pink	— —	— —	— —	— —

Approximate colors of actinide ions in aqueous solution^[83]
Oxidation state	89	90	91	92	93	94	95	96	97	98	99
+3	Ac³⁺	Th³⁺	Pa³⁺	U³⁺	Np³⁺	Pu³⁺	Am³⁺	Cm³⁺	Bk³⁺	Cf³⁺	Es³⁺
+4		Th⁴⁺	Pa⁴⁺	U⁴⁺	Np⁴⁺	Pu⁴⁺	Am⁴⁺	Cm⁴⁺	Bk⁴⁺	Cf⁴⁺
+5			PaO+ 2	UO+ 2	NpO+ 2	PuO+ 2	AmO+ 2
+6				UO2+ 2	NpO2+ 2	PuO2+ 2	AmO2+ 2
+7					NpO3+ 2	PuO3+ 2	[AmO₆]^5-

Physical properties


Major crystal structures of some actinides vs. temperature	Metallic and ionic radii of actinides^[81]

A pellet of ²³⁸PuO₂ to be used in a radioisotope thermoelectric generator for either the Cassini or Galileo mission. The pellet produces 62 watts of heat and glows because of the heat generated by the radioactive decay (primarily α). Photo is taken after insulating the pellet under a graphite blanket for minutes and removing the blanket.

Californium

Actinides are typical metals. All of them are soft and have a silvery color (but tarnish in air),^[84] relatively high density and plasticity. Some of them can be cut with a knife. Their electrical resistivity varies between 15 and 150 µOhm·cm.^[81] The hardness of thorium is similar to that of soft steel, so heated pure thorium can be rolled in sheets and pulled into wire. Thorium is nearly half as dense as uranium and plutonium, but is harder than either of them. All actinides are radioactive, paramagnetic, and, with the exception of actinium, have several crystalline phases: plutonium has seven, and uranium, neptunium and californium three. Crystal structures of protactinium, uranium, neptunium and plutonium do not have clear analogs among the lanthanides and are more similar to those of the 3d-transition metals.^[70]

All actinides are pyrophoric, especially when finely divided, that is, they spontaneously ignite upon reaction with air.^[84] The melting point of actinides does not have a clear dependence on the number of f-electrons. The unusually low melting point of neptunium and plutonium (~640 °C) is explained by hybridization of 5f and 6d orbitals and the formation of directional bonds in these metals.^[70]

Comparison of ionic radii of lanthanides and actinides^[85]
Lanthanides	Ln³⁺, Å	Actinides	An³⁺, Å	An⁴⁺, Å
Lanthanum	1.061	Actinium	1.11	–
Cerium	1.034	Thorium	1.08	0.99
Praseodymium	1.013	Protactinium	1.05	0.93
Neodymium	0.995	Uranium	1.03	0.93
Promethium	0.979	Neptunium	1.01	0.92
Samarium	0.964	Plutonium	1.00	0.90
Europium	0.950	Americium	0.99	0.89
Gadolinium	0.938	Curium	0.98	0.88
Terbium	0.923	Berkelium	-	-
Dysprosium	0.908	Californium	-	-
Holmium	0.894	Einsteinium	-	-
Erbium	0.881	Fermium	-	-
Thulium	0.869	Mendelevium	-	-
Ytterbium	0.858	Nobelium	-	-
Lutetium	0.848	Lawrencium	-	-

Chemical properties

Like the lanthanides, all actinides are highly reactive with halogens and chalcogens; however, the actinides react more easily. Actinides, especially those with a small number of 5f-electrons, are prone to hybridization. This is explained by the similarity of the electron energies at the 5f, 7s and 6d shells. Most actinides exhibit a larger variety of valence states, and the most stable are +6 for uranium, +5 for protactinium and neptunium, +4 for thorium and plutonium and +3 for actinium and other actinides.^[86]

Chemically, actinium is similar to lanthanum, which is explained by their similar ionic radii and electronic structure. Like lanthanum, actinium has oxidation of +3, but it is less reactive and has more pronounced basic properties. Among other trivalent actinides Ac³⁺ is least acidic, i.e. has the weakest tendency to hydrolyze in aqueous solutions.^[29]^[70]

Thorium is rather active chemically. Owing to lack of electrons on 6d and 5f orbitals, the tetravalent thorium compounds are colorless. At pH < 3, the solutions of thorium salts are dominated by the cations [Th(H₂O)₈]⁴⁺. The Th⁴⁺ ion is relatively large, and depending on the coordination number can have a radius between 0.95 and 1.14 Å. As a result, thorium salts have a weak tendency to a hydrolysis. The distinctive ability of thorium salts is their high solubility, not only in water, but also in polar organic solvents.^[70]

Protactinium exhibits two valence states; the +5 is stable, and the +4 state easily oxidizes to protactinium(V). Thus tetravalent protactinium in solutions is obtained by the action of strong reducing agents in a hydrogen atmosphere. Tetravalent protactinium is chemically similar to uranium(IV) and thorium(IV). Fluorides, phosphates, hypophosphate, iodate and phenylarsonates of protactinium(IV) are insoluble in water and dilute acids. Protactinium forms soluble carbonates. The hydrolytic properties of pentavalent protactinium are close to those of tantalum(V) and niobium(V). The complex chemical behavior of protactinium is a consequence of the start of the filling of the 5f shell in this element.^[62]

Uranium has a valence from 3 to 6, the last being most stable. In the hexavalent state, uranium is very similar to the sixth group elements. Many compounds of uranium(IV) and uranium(VI) are nonstoichiometric, i.e. have variable composition. For example, the actual chemical formula of uranium dioxide is UO_2+x, where x varies between −0.4 and 0.32. Uranium(VI) compounds are weak oxidants. Most of them contain the linear "uranyl" group, UO2+
2. Between 4 to 6 ligands can be accommodated in an equatorial plane perpendicular to the uranyl group. The uranyl group acts as a hard acid and forms stronger complexes with oxygen-donor ligands than with nitrogen-donor ligands. NpO2+
2 and PuO2+
2 are also the common form of Np and Pu in the +6 oxidation state. Uranium(IV) compounds exhibit reducing properties, e.g., they are easily oxidized by atmospheric oxygen. Uranium(III) is a very strong reducing agent. Owing to the presence of d-shell, uranium (as well as many other actinides) forms organometallic compounds, such as U^III(C₅H₅)₃ and U^IV(C₅H₅)₄.^[70]^[87]

Neptunium has valence states from 3 to 7, which can be simultaneously observed in solutions. The most stable state in solution is +5, but the valence +4 is preferred in solid neptunium compounds. Neptunium metal is very reactive. Ions of neptunium are prone to hydrolysis and formation of coordination compounds.^[37]

Plutonium also exhibits the valence between 3 and 7, and thus is chemically similar to neptunium and uranium. It is highly reactive, and quickly forms an oxide film in air. Plutonium reacts with hydrogen even at temperatures as low as 25–50 °C; it also easily forms halides and intermetallic compounds. Hydrolysis reactions of plutonium ions of different oxidation states are quite diverse. Plutonium(V) can enter polymerization reactions.^[88]^[89]

The largest chemical diversity among actinides is observed in americium, which can have valence between 2 and 6. Divalent americium is obtained only in dry compounds and non-aqueous solutions (acetonitrile). Oxidation states +3, +5 and +6 are typical for aqueous solutions, but also in the solid state. Tetravalent americium forms stable solid compounds (dioxide, fluoride and hydroxide) as well as complexes in aqueous solutions. It was reported that in alkaline solution americium can be oxidized to the heptavalent state, but these data proved erroneous. The most stable valence of americium is 3 in the aqueous solutions and 3 or 4 in solid compounds.^[90]

Valence 3 is dominant in all subsequent elements up to lawrencium (with the possible exception of nobelium). Curium can be tetravalent in solids (fluoride, dioxide). Berkelium, along with a valence of +3, also shows the valence of +4, more stable than that of curium; the valence 4 is observed in solid fluoride and dioxide. The stability of Bk⁴⁺ in aqueous solution is close to that of Ce⁴⁺. Only valence 3 was observed for californium, einsteinium and fermium. The divalent state is proven for mendelevium and nobelium, and in nobelium it is more stable than the trivalent state. Lawrencium shows valence 3 both in solutions and solids.^[90]

The redox potential increases from −0.32 V in uranium, through 0.34 V (Np) and 1.04 V (Pu) to 1.34 V in americium revealing the increasing reduction ability of the An⁴⁺ ion from americium to uranium. All actinides form AnH₃ hydrides of black color with salt-like properties. Actinides also produce carbides with the general formula of AnC or AnC₂ (U₂C₃ for uranium) as well as sulfides An₂S₃ and AnS₂.^[86]

Uranyl nitrate (UO₂(NO₃)₂)
Aqueous solutions of uranium III, IV, V, VI salts
Aqueous solutions of neptunium III, IV, V, VI, VII salts
Aqueous solutions of plutonium III, IV, V, VI, VII salts
Uranium tetrachloride
Uranium hexafluoride
U₃O₈ (yellowcake)

Compounds

Oxides and hydroxides

Oxides of actinides^[29]^[37]^[62]^[91]^[92]
Compound	Color	Crystal symmetry, type	Lattice constants, Å			Density, g/cm³	Temperature, °C
Compound	Color	Crystal symmetry, type	a	b	c	Density, g/cm³	Temperature, °C
Ac₂O₃	White	Hexagonal, La₂O₃	4.07	-	6.29	9.19	–
PaO₂	-	Cubic, CaF₂	5.505	-	-	-	-
Pa₂O₅	White	cubic, CaF₂ Cubic Tetragonal Hexagonal Rhombohedral Orthorhombic	5.446 10.891 5.429 3.817 5.425 6.92	- - - - - 4.02	- 10.992 5.503 13.22 - 4. 18	-	700 700–1100 1000 1000–1200 1240–1400 –
ThO₂	Colorless	Cubic	5.59	-	-	9.87	–
UO₂	Black-brown	Cubic	5.47	-	-	10.9	–
NpO₂	Greenish-brown	Cubic, CaF₂	5.424	-	-	11.1	–
PuO	Black	Cubic, NaCl	4.96	-	-	13.9	–
PuO₂	Olive green	Cubic	5.39	-	-	11.44	–
Am₂O₃	Red-brown Red-brown	Cubic, Mn₂O₃ Hexagonal, La₂O₃	11.03 3.817	-	- 5.971	10.57 11.7	–
AmO₂	Black	Cubic, CaF₂	5.376	-	-	-	-
Cm₂O₃	White^[93] - -	Cubic, Mn₂O₂ Hexagonal, LaCl₃ Monoclinic, Sm₂O₃	11.01 3.80 14.28	- - 3.65	- 6 8.9	11.7	–
CmO₂	Black	Cubic, CaF₂	5.37	-	-	-	-
Bk₂O₃	Light brown	Cubic, Mn₂O₃	10.886	-	-	-	-
BkO₂	Red-brown	Cubic, CaF₂	5.33	-	-	-	-
Cf₂O₃^[94]	Colorless Yellowish -	Cubic, Mn₂O₃ Monoclinic, Sm₂O₃ Hexagonal, La₂O₃	10.79 14.12 3.72	- 3.59 -	- 8.80 5.96	-	-
CfO₂	Black	Cubic	5.31	-	-	-	-
Es₂O₃	-	Cubic, Mn₂O₃ Monoclinic Hexagonal, La₂O₃	10.07 14.1 3.7	- 3.59 -	- 8.80 6	-	-

Approximate colors of actinide oxides (most stable are bolded)^[95]
Oxidation state	89	90	91	92	93	94	95	96	97	98	99
+3						Pu₂O₃	Am₂O₃	Cm₂O₃	Bk₂O₃	Cf₂O₃	Es₂O₃
+4		ThO₂	PaO₂	UO₂	NpO₂	PuO₂	AmO₂	CmO₂	BkO₂	CfO₂
+5			Pa₂O₅	U₂O₅	Np₂O₅
+6				U₃O₈
+6				UO₃

Dioxides of some actinides
Chemical formula	ThO₂	PaO₂	UO₂	NpO₂	PuO₂	AmO₂	CmO₂	BkO₂	CfO₂
CAS-number	1314-20-1	12036-03-2	1344-57-6	12035-79-9	12059-95-9	12005-67-3	12016-67-0	12010-84-3	12015-10-0
Molar mass	264.04	263.035	270.03	269.047	276.063	275.06	270–284**	279.069	283.078
Melting point^[96]	3390 °C		2865 °C	2547 °C	2400 °C	2175 °C
Crystal structure	An⁴⁺: __ / O²⁻: __
Space group	Fm3m
Coordination number	An[8], O[4]

An – actinide

- Depending on the isotopes

Some actinides can exists in several oxide forms such as An₂O₃, AnO₂, An₂O₅ and AnO₃. For all actinides, oxides AnO₃ are amphoteric and An₂O₃, AnO₂ and An₂O₅ are basic, they easily react with water, forming bases:^[86]

An₂O₃ + 3 H₂O → 2 An(OH)₃.

These bases are poorly soluble in water and by their activity are close to the hydroxides of rare-earth metals. The strongest base is of actinium. All compounds of actinium are colorless, except for black actinium sulfide (Ac₂S₃).^[86] Dioxides of tetravalent actinides crystallize in the cubic system, same as in calcium fluoride.

Thorium reacting with oxygen exclusively forms dioxide:

Thorium dioxide is a refractory material with the highest melting point among any known oxide (3390 °C).^[95] Adding 0.8–1% ThO₂ to tungsten stabilizes its structure, so the doped filaments have better mechanical stability to vibrations. To dissolve ThO₂ in acids, it is heated to 500–600 °C; heating above 600 °C produces a very resistant to acids and other reagents form of ThO₂. Small addition of fluoride ions catalyses dissolution of thorium dioxide in acids.

Two protactinium oxides were obtained: PaO₂ (black) and Pa₂O₅(white); the former is isomorphic with ThO₂ and the latter is easier to obtain. Both oxides are basic, and Pa(OH)₅ is a weak, poorly soluble base.^[86]

Decomposition of certain salts of uranium, for example UO₂(NO₃)·6H₂O in air at 400 °C, yields orange or yellow UO₃.^[95] This oxide is amphoteric and forms several hydroxides, the most stable being UO₂(OH)₂. Reaction of uranium(VI) oxide with hydrogen results in uranium dioxide, which is similar in its properties with ThO₂. This oxide is also basic and corresponds to the uranium hydroxide (U(OH)₄).^[86]

Plutonium, neptunium and americium form two basic oxides: An₂O₃ and AnO₂. Neptunium trioxide is unstable; thus, only Np₃O₈ could be obtained so far. However, the oxides of plutonium and neptunium with the chemical formula AnO₂ and An₂O₃ are well characterized.^[86]

Salts

Trichlorides of some actinides^[97]
Chemical formula	AcCl₃	UCl₃	NpCl₃	PuCl₃	AmCl₃	CmCl₃	BkCl₃	CfCl₃
CAS-number	22986-54-5	10025-93-1	20737-06-8	13569-62-5	13464-46-5	13537-20-7	13536-46-4	13536-90-8
Molar mass	333.386	344.387	343.406	350.32	349.42	344–358**	353.428	357.438
Melting point		837 °C	800 °C	767 °C	715 °C	695 °C	603 °C	545 °C
Boiling point		1657 °C		1767 °C	850 °C
Crystal structure	An³⁺: __ / Cl⁻: __
Space group	P6₃/m
Coordination number	An*[9], Cl [3]
Lattice constants	a = 762 pm c = 455 pm	a = 745.2 pm c = 432.8 pm		a = 739.4 pm c = 424.3 pm	a = 738.2 pm c = 421.4 pm	a = 726 pm c = 414 pm	a = 738.2 pm c = 412.7 pm	a = 738 pm c = 409 pm

*An – actinide

- Depending on the isotopes

Actinide fluorides^[37]^[62]^[92]^[97]^[98]
Compound	Color	Crystal symmetry, type	Lattice constants, Å			Density, g/cm³
Compound	Color	Crystal symmetry, type	a	b	c	Density, g/cm³
AcF₃	White	Hexagonal, LaF₃	4.27	-	7.53	7.88
PaF₄	Dark brown	Monoclinic	12.7	10.7	8.42	–
PaF₅	Black	Tetragonal, β-UF₅	11.53	-	5.19	–
ThF₄	Colorless	Monoclinic	13	10.99	8.58	5.71
UF₃	Reddish-purple	Hexagonal	7.18	-	7.34	8.54
UF₄	Green	Monoclinic	11.27	10.75	8.40	6.72
α-UF₅	Bluish	Tetragonal	6.52	-	4.47	5.81
β-UF₅	Bluish	Tetragonal	11.47	-	5.20	6.45
UF₆	Yellowish	Orthorhombic	9.92	8.95	5.19	5.06
NpF₃	Black or purple	Hexagonal	7.129	-	7.288	9.12
NpF₄	Light green	Monoclinic	12.67	10.62	8.41	6.8
NpF₆	Orange	Orthorhombic	9.91	8.97	5.21	5
PuF₃	Violet-blue	Trigonal	7.09	-	7.25	9.32
PuF₄	Pale brown	Monoclinic	12.59	10.57	8.28	6.96
PuF₆	Red-brown	Orthorhombic	9.95	9.02	3.26	4.86
AmF₃	Pink or light beige	hexagonal, LaF₃	7.04^[72]^[99]	-	7.255	9.53
AmF₄	Orange-red	Monoclinic	12.53	10.51	8.20	–
CmF₃	From brown to white	Hexagonal	4.041	-	7.179	9.7
CmF₄	Yellow	Monoclinic, UF₄	12.51	10.51	8.20	–
BkF₃	Yellow-green	Trigonal, LaF₃ Orthorhombic, YF₃	6.97 6.7	- 7.09	7.14 4.41	10.15 9.7
BkF₄	-	Monoclinic, UF₄	12.47	10.58	8.17	–
CfF₃	- -	Trigonal, LaF₃ Orthorhombic, YF₃	6. 94 6.65	- 7.04	7.10 4.39	–
CfF₄	- -	Monoclinic, UF₄ Monoclinic, UF₄	1.242 1.233	1.047 1.040	8.126 8.113	–

Einsteinium triiodide glowing in the dark

Actinides easily react with halogens forming salts with the formulas MX₃ and MX₄ (X = halogen). So the first berkelium compound, BkCl₃, was synthesized in 1962 with an amount of 3 nanograms. Like the halogens of rare earth elements, actinide chlorides, bromides, and iodides are water soluble, and fluorides are insoluble. Uranium easily yields a colorless hexafluoride, which sublimates at a temperature of 56.5 °C; because of its volatility, it is used in the separation of uranium isotopes with gas centrifuge or gaseous diffusion. Actinide hexafluorides have properties close to anhydrides. They are very sensitive to moisture and hydrolyze forming AnO₂F₂.^[100] The pentachloride and black hexachloride of uranium were synthesized, but they are both unstable.^[86]

Action of acids on actinides yields salts, and if the acids are non-oxidizing then the actinide in the salt is in low-valence state:

U + 2 H₂SO₄ → U (SO₄)₂ + 2 H₂

2 Pu + 6 HCl → 2 PuCl₃ + 3 H₂

However, in these reactions the regenerating hydrogen can react with the metal, forming the corresponding hydride. Uranium reacts with acids and water much more easily than thorium.^[86]

Actinide salts can also be obtained by dissolving the corresponding hydroxides in acids. Nitrates, chlorides, sulfates and perchlorates of actinides are water soluble. When crystallizing from aqueous solutions, these salts forming a hydrates, such as Th(NO₃)₄·6H₂O, Th(SO₄)₂·9H₂O and Pu₂(SO₄)₃·7H₂O. Salts of high-valence actinides easily hydrolyze. So, colorless sulfate, chloride, perchlorate and nitrate of thorium transform into basic salts with formulas Th(OH)₂SO₄ and Th(OH)₃NO₃. The solubility and insolubility of trivalent and tetravalent actinides is like that of lanthanide salts. So phosphates, fluorides, oxalates, iodates and carbonates of actinides are weakly soluble in water; they precipitate as hydrates, such as ThF₄·3H₂O and Th(CrO₄)₂·3H₂O.^[86]

Actinides with oxidation state +6, except for the AnO₂²⁺-type cations, form [AnO₄]^2–, [An₂O₇]^2– and other complex anions. For example, uranium, neptunium and plutonium form salts of the Na₂UO₄ (uranate) and (NH₄)₂U₂O₇ (diuranate) types. In comparison with lanthanides, actinides more easily form coordination compounds, and this ability increases with the actinide valence. Trivalent actinides do not form fluoride coordination compounds, whereas tetravalent thorium forms K₂ThF₆, KThF₅, and even K₅ThF₉ complexes. Thorium also forms the corresponding sulfates (for example Na₂SO₄·Th (SO₄)₂·5H₂O), nitrates and thiocyanates. Salts with the general formula An₂Th(NO₃)₆·nH₂O are of coordination nature, with the coordination number of thorium equal to 12. Even easier is to produce complex salts of pentavalent and hexavalent actinides. The most stable coordination compounds of actinides – tetravalent thorium and uranium – are obtained in reactions with diketones, e.g. acetylacetone.^[86]

Applications

Interior of a smoke detector containing americium-241.

While actinides have some established daily-life applications, such as in smoke detectors (americium)^[101]^[102] and gas mantles (thorium),^[77] they are mostly used in nuclear weapons and use as a fuel in nuclear reactors.^[77] The last two areas exploit the property of actinides to release enormous energy in nuclear reactions, which under certain conditions may become self-sustaining chain reaction.

Self-illumination of a nuclear reactor by Cherenkov radiation.

The most important isotope for nuclear power applications is uranium-235. It is used in the thermal reactor, and its concentration in natural uranium does not exceed 0.72%. This isotope strongly absorbs thermal neutrons releasing much energy. One fission act of 1 gram of ²³⁵U converts into about 1 MW·day. Of importance, is that ²³⁵U emits more neutrons than it absorbs;^[103] upon reaching the critical mass, ²³⁵U enters into a self-sustaining chain reaction.^[70] Typically, uranium nucleus is divided into two fragments with the release of 2–3 neutrons, for example:

Other promising actinide isotopes for nuclear power are thorium-232 and its product from the thorium fuel cycle, uranium-233.

Nuclear reactor^[70]^[104]^[105]
The core of any nuclear reactor contains a set of hollow metal rods, usually made of zirconium alloys, filled with nuclear fuel cells – mostly oxide, carbide, nitride or monosulfide of uranium, plutonium or thorium, or their mixture (the so-called MOX fuel). The most common fuel is oxide of uranium-235. Fast neutrons are slowed by moderators, which contain water, carbon, deuterium, or beryllium, as thermal neutrons to increase the efficiency of their interaction with uranium-235. The rate of nuclear reaction is controlled by introducing additional rods made of boron or cadmium or a liquid absorbent, usually boric acid. Reactors for plutonium production are called breeder reactor or breeders; they have a different design and use fast neutrons.

Emission of neutrons during the fission of uranium is important not only for maintaining the nuclear chain reaction, but also for the synthesis of the heavier actinides. Uranium-239 converts via β-decay into plutonium-239, which, like uranium-235, is capable of spontaneous fission. The world's first nuclear reactors were built not for energy, but for producing plutonium-239 for nuclear weapons.

About half of the produced thorium is used as the light-emitting material of gas mantles.^[77] Thorium is also added into multicomponent alloys of magnesium and zinc. So the Mg-Th alloys are light and strong, but also have high melting point and ductility and thus are widely used in the aviation industry and in the production of missiles. Thorium also has good electron emission properties, with long lifetime and low potential barrier for the emission.^[103] The relative content of thorium and uranium isotopes is widely used to estimate the age of various objects, including stars (see radiometric dating).^[106]

The major application of plutonium has been in nuclear weapons, where the isotope plutonium-239 was a key component due to its ease of fission and availability. Plutonium-based designs allow reducing the critical mass to about a third of that for uranium-235.^[107] The "Fat Man"-type plutonium bombs produced during the Manhattan Project used explosive compression of plutonium to obtain significantly higher densities than normal, combined with a central neutron source to begin the reaction and increase efficiency. Thus only 6.2 kg of plutonium was needed for an explosive yield equivalent to 20 kilotons of TNT.^[108] (See also Nuclear weapon design.) Hypothetically, as little as 4 kg of plutonium—and maybe even less—could be used to make a single atomic bomb using very sophisticated assembly designs.^[109]

Plutonium-238 is potentially more efficient isotope for nuclear reactors, as it has smaller critical mass than uranium-235, but releases much more thermal energy (0.56 W/g).^[102]^[110] However, its application is limited by the high price (about 1000 USD/g). This isotope has been used in thermopiles and water distillation systems of some space satellites and stations. So Galileo and Apollo spacecrafts (e.g. Apollo 14^[111]) had heaters powered by kilogram quantities of plutonium-238 oxide; this heat is also transformed into electricity with thermopiles. The decay of plutonium-238 is produced relatively harmless alpha particles and is not accompanied by gamma-irradiation. Therefore and this isotope (~160 mg) is used as the energy source in heart pacemakers where it lasts about 5 times longer than conventional batteries.^[102]

Actinium-227 is used as a neutron source. Its high specific energy (14.5 W/g) and the possibility of obtaining significant quantities of thermally stable compounds are attractive for use in long-lasting thermoelectric generators for remote use. ²²⁸Ac is used as an indicator of radioactivity in chemical research, as it emits high-energy electrons (2.18 MeV) that can be easily detected. ²²⁸Ac-²²⁸Ra mixtures are widely used as an intense gamma-source in industry and medicine.^[29]

Development of self-glowing actinide-doped materials with durable crystalline matrices is a new area of actinide utilization as the addition of alpha-emitting radionuclides to some glasses and crystals may confer luminescence.^[112]

Toxicity

Schematic illustration of penetration of radiation through sheets of paper, aluminium and lead brick

Periodic table with elements colored according to the half-life of their most stable isotope.

Elements which contain at least one stable isotope.

Radioactive elements: the most stable isotope is very long-lived, with a half-life of over four million years.

Radioactive elements: the most stable isotope has half-life between 800 and 34.000 years.

Radioactive elements: the most stable isotope has half-life between one day and 103 years.

Highly radioactive elements: the most stable isotope has half-life between several minutes and one day.

Extremely radioactive elements: the most stable isotope has half-life less than several minutes. Very little is known about these elements due to their extreme instability and radioactivity.

Radioactive substances can harm human health via (i) local skin contamination, (ii) internal exposure due to ingestion of radioactive isotopes, and (iii) external overexposure by β-activity and γ-radiation. Together with radium and transuranium elements, actinium is one of the most dangerous radioactive poisons with high specific α-activity. The most important feature of actinium is its ability to accumulate and remain in the surface layer of skeletons. At the initial stage of poisoning, actinium accumulates in the liver. Another danger of actinium is that it undergoes radioactive decay faster than being excreted. Adsorption from the digestive tract is much smaller (~0.05%) for actinium than radium.^[29]

Protactinium in the body tends to accumulate in the kidneys and bones. The maximum safe dose of protactinium in the human body is 0.03 µCi that corresponds to 0.5 micrograms of ²³¹Pa. This isotope, which might be present in the air as aerosol, is 2.5×10⁸ times more toxic than hydrocyanic acid.^[62]

Plutonium, when entering the body through air, food or blood (e.g. a wound), mostly settles in the lungs, liver and bones with only about 10% going to other organs, and remains there for decades. The long residence time of plutonium in the body is partly explained by its poor solubility in water. Some isotopes of plutonium emit ionizing α-radiation, which damages the surrounding cells. The median lethal dose (LD₅₀) for 30 days in dogs after intravenous injection of plutonium is 0.32 milligram per kg of body mass, and thus the lethal dose for humans is approximately 22 mg for a person weighing 70 kg; the amount for respiratory exposure should be approximately four times greater. Another estimate assumes that plutonium is 50 times less toxic than radium, and thus permissible content of plutonium in the body should be 5 µg or 0.3 µCi. Such amount is nearly invisible in under microscope. After trials on animals, this maximum permissible dose was reduced to 0.65 µg or 0.04 µCi. Studies on animals also revealed that the most dangerous plutonium exposure route is through inhalation, after which 5–25% of inhaled substances is retained in the body. Depending on the particle size and solubility of the plutonium compounds, plutonium is localized either in the lungs or in the lymphatic system, or is absorbed in the blood and then transported to the liver and bones. Contamination via food is the least likely way. In this case, only about 0.05% of soluble 0.01% insoluble compounds of plutonium absorbs into blood, and the rest is excreted. Exposure of damaged skin to plutonium would retain nearly 100% of it.^[88]

Using actinides in nuclear fuel, sealed radioactive sources or advanced materials such as self-glowing crystals has many potential benefits. However, a serious concern is the extremely high radiotoxicity of actinides and their migration in the environment.^[113] Use of chemically unstable forms of actinides in MOX and sealed radioactive sources is not appropriate by modern safety standards. There is a challenge to develop stable and durable actinide-bearing materials, which provide safe storage, use and final disposal. A key need is application of actinide solid solutions in durable crystalline host phases.^[112]

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^ ^a ^b ^c F. Weigel, J. Katz, G. Seaborg (1997). The Chemistry of the Actinide Elements. 2. Moscow: Mir. ISBN 5-03-001885-9.
^ Thorium, USGS Mineral Commodities
^ ^a ^b ^c John Emsley (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.
^ ^a ^b ^c ^d ^e ^f ^g Golub, pp. 215–217
^ Greenwood, pp. 1255, 1261
^ ^a ^b ^c ^d ^e Greenwood, p. 1255
^ A. E. van Arkel; de Boer, J. H. (1925). "Darstellung von reinem Titanium-, Zirkonium-, Hafnium- und Thoriummetall" (in German). Zeitschrift für anorganische und allgemeine Chemie 148 (1): 345–350. doi:10.1002/zaac.19251480133.
^ I.L. Knunyants (1961). Short Chemical Encyclopedia. 1. Moscow: Soviet Encyclopedia.
^ Golub, pp. 218–219
^ ^a ^b ^c Greenwood, p. 1263
^ Peterson, Ivars (7 December 1991). "Uranium displays rare type of radioactivity". Science News. http://findarticles.com/p/articles/mi_m1200/is_n23_v140/ai_11701241/.
^ Greenwood, p. 1265
^ ^a ^b Greenwood, p. 1264
^ Myasoedov, pp. 30–31
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Golub, pp. 222–227
^ Greenwood, p. 1278
^ ^a ^b B.A. Nadykto and L.F. Timofeeva, ed. (2003). Plutonium. Fundamental Problems. 1. Sarov: VNIIEF. ISBN 5-9515-0024-9.
^ M. S. Milyukova (1965). Analytical chemistry of plutonium. Moscow: Nauka. ISBN 0-250-39918-0.
^ ^a ^b Myasoedov, pp. 25–29
^ Myasoedov, p. 88
^ ^a ^b "Таблица Inorganic and Coordination compounds" (in Russian). http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/01_osnovnye_svoystva_neorganicheskikh_organicheskikh_i_elementoorganicheskikh_soedineniy. Retrieved 11 July 2010.
^ According to other sources, cubic sesquioxide of curium is olive-green. See "Соединения curium site XuMuK.ru" (in Russian). Archived from the original on 18 August 2010. http://www.xumuk.ru/encyklopedia/2248.html. Retrieved 11 July 2010.
^ The atmosphere during the synthesis affects the lattice parameters, which might be due to non-stoichiometry as a result of oxidation or reduction of the trivalent californium. Main form is the cubic oxide of californium(III).
^ ^a ^b ^c Greenwood, p. 1268
^ L.R. Morss, Norman M. Edelstein and Jean Fuger (2011). The Chemistry of the Actinide and Transactinide Elements (Set Vol.1–6). Springer. pp. 2139–. ISBN 978-94-007-0210-3. http://books.google.com/books?id=9vPuV3A0UGUC&pg=PA2139.
^ ^a ^b Greenwood, p. 1270
^ Myasoedov, pp. 96–99
^ Nave, S.; Haire, R.; Huray, Paul (1983). "Magnetic properties of actinide elements having the 5f⁶ and 5f⁷ electronic configurations". Physical Review B 28: 2317. Bibcode 1983PhRvB..28.2317N. doi:10.1103/PhysRevB.28.2317.
^ Greenwood, p.1269
^ Smoke Detectors and Americium, Nuclear Issues Briefing Paper 35, May 2002
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^ M. I. Ojovan, W.E. Lee (2005). An Introduction to Nuclear Waste Immobilisation. Amsterdam: Elsevier. ISBN 0080444628. http://books.google.com/books?id=vQkQnmo_bE0C&printsec=frontcover.

Bibliography

Golub, A. M. (1971). Общая и неорганическая химия (General and Inorganic Chemistry). 2.
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419.
Myasoedov, B. (1972). Analytical chemistry of transplutonium elements. Moscow: Nauka. ISBN 0-470-62715-8.

External links

Lawrence Berkeley Laboratory image of historic periodic table by Seaborg showing actinide series for the first time
Lawrence Livermore National Laboratory, Uncovering the Secrets of the Actinides
Los Alamos National Laboratory, Actinide Research Quarterly

English Journal

Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: The hydration of Cf(3+).

Galbis E1, Hernández-Cobos J2, Pappalardo RR1, Marcos ES1.
The Journal of chemical physics.J Chem Phys.2014 Jun 7;140(21):214104. doi: 10.1063/1.4879549.
This work proposes a new methodology to build interaction potentials between a highly charged metal cation and water molecules. These potentials, which can be used in classical computer simulations, have been fitted to reproduce quantum mechanical interaction energies (MP2 and BP86) for a wide range
PMID 24907987

Hydration properties of Cm(III) and Th(IV) combining coordination free energy profiles with electronic structure analysis.

Spezia R1, Jeanvoine Y, Beuchat C, Gagliardi L, Vuilleumier R.
Physical chemistry chemical physics : PCCP.Phys Chem Chem Phys.2014 Mar 28;16(12):5824-32. doi: 10.1039/c3cp54958e. Epub 2014 Feb 18.
The hydration structure of two actinoid ions of different charge, Cm(III) and Th(IV), was investigated. Density Functional Theory, DFT-based molecular dynamics and the single sweep method were used to obtain free energy landscapes of ion-water coordination. Free energy curves as a function of the io
PMID 24535290

An overview of results obtained in intercomparison exercises for determination of actinides.

Benedik L.
Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.Appl Radiat Isot.2013 Nov;81:10-3. doi: 10.1016/j.apradiso.2013.03.035. Epub 2013 Mar 21.
In recent years the Jožef Stefan Institute participated in numerous intercomparison exercises for determination of natural and man-made radionuclides. The reported values were mostly in good agreement with the resulting reference values. This paper describes an analysis of the measurement results o
PMID 23566808

Radionuclide decorporation: matching the biokinetics of actinides by transdermal delivery of pro-chelators.

Zhang Y1, Sadgrove MP, Mumper RJ, Jay M.
The AAPS journal.AAPS J.2013 Oct;15(4):1180-8. doi: 10.1208/s12248-013-9527-x. Epub 2013 Aug 30.
The threat of nuclear terrorism by the deliberate detonation of a nuclear weapon or radiological dispersion device ("dirty bomb") has made emergency response planning a priority. The only FDA-approved treatments for contamination with isotopes of the transuranic elements Am, Pu, and Cm are the Ca an
PMID 23990504

Japanese Journal

Novel Soft–Hard Donor Ligand, NTAamide, for Mutual Separation of Trivalent Actinoids and Lanthanoids

, , ,
Chemistry Letters 42(1), 91-92, 2013
… New reagent, N,N,N′,N′,N′′,N′′-hexaoctylnitrilotriacetamide (NTAamide(C8)), was synthesized and examined for actinoid and lanthanoid extractions. …
NAID 130004426729

エクスパンデットベッドカラムクロマトグラフィーのマイナーアクチノイド分離プロセスへの適応性

小川剛,新井剛,永山勝久,渡部創,佐野雄一,野村和則
日本イオン交換学会誌 24(2), 52-59, 2013
軽水炉及び高速増殖炉（FBR）から発生する使用済核燃料において，高レベル放射性廃棄物（High-Level radioactive Waste; HLW）の処理・処分法の確立は極めて大きな開発課題である。特に放射性廃棄物を地層処分するためには，環境負荷軽減や処分場の占有面積低減等の観点から，HLW に含まれる長半減期核種であるマイナーアクチノイド（MA）の分離が重要となる。現在，HLW からの M …
NAID 130003375928

核分裂片加速途中の中性子放出を考慮した即発中性子スペクトル：マイナーアクチニドの場合

日置昌吾,大澤孝明
日本原子力学会　年会・大会予稿集 2012f(0), 159, 2012
核種変換の研究においてマイナーアクチニドの即発中性子スペクトル（PFNS）の理論計算精度向上が重要な課題となっている。松本らによる核分裂片加速途中における中性子放出（NEDA）を考慮したPFNS計算モデルをマイナーアクチニドに適用した結果について報告する。
NAID 130005051356

トリウム燃料軽水炉の崩壊熱解析

臼井真人,高木直行,吉田正
日本原子力学会　年会・大会予稿集 2012f(0), 145, 2012
近年,レアアースと共に採掘され,放射性廃棄物として扱われているトリウムを核燃料して利用することに期待が高まっている。原子力発電において崩壊熱解析は重要な検討項目の一つであるが,トリウム燃料崩壊熱解析の研究はあまり進められていない。そこで,トリウム燃料を軽水炉で使用した場合の崩壊熱解析を行い,ウラン燃料との比較を行うとともに,熱源として支配的な核種の同定を行う。また弥生炉とのベンチマーク解析を行い計 …
NAID 130005051341

★リンクテーブル★

リンク元	「アクチノイド」「actinide」
拡張検索	「actinoid series element」

「アクチノイド」

　　[★]

英: actinoid
関: アクチニド、アクチノイド系列元素

「actinide」

　　[★]

アクチニド

関: actinoid、actinoid series element

「actinoid series element」

　　[★]

アクチノイド系列元素

関: actinide、actinoid

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[59] Myasoedov, pp. 19–21

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[g1254-61] Greenwood, p. 1254

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[WNA-WUM-71] "World Uranium Mining". World Nuclear Association. Archived from the original on 26 June 2010. http://www.world-nuclear.org/info/inf23.html. Retrieved 11 June 2010.

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[73] Thorium, USGS Mineral Commodities

[emsley-74] John Emsley (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.

[g215-75] ^ ^a ^b ^c ^d ^e ^f ^g Golub, pp. 215–217

[76] Greenwood, pp. 1255, 1261

[g1255-77] Greenwood, p. 1255

[78] A. E. van Arkel; de Boer, J. H. (1925). "Darstellung von reinem Titanium-, Zirkonium-, Hafnium- und Thoriummetall" (in German). Zeitschrift für anorganische und allgemeine Chemie 148 (1): 345–350. doi:10.1002/zaac.19251480133.

[I._L._Knunyants-79] I.L. Knunyants (1961). Short Chemical Encyclopedia. 1. Moscow: Soviet Encyclopedia.

[g218-80] Golub, pp. 218–219

[g1263-81] Greenwood, p. 1263

[82] Peterson, Ivars (7 December 1991). "Uranium displays rare type of radioactivity". Science News. http://findarticles.com/p/articles/mi_m1200/is_n23_v140/ai_11701241/.

[g1265-83] Greenwood, p. 1265

[g1264-84] Greenwood, p. 1264

[85] Myasoedov, pp. 30–31

[g222-86] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k Golub, pp. 222–227

[g1278-87] Greenwood, p. 1278

[Plutoniy-88] B.A. Nadykto and L.F. Timofeeva, ed. (2003). Plutonium. Fundamental Problems. 1. Sarov: VNIIEF. ISBN 5-9515-0024-9.

[Himiya_plutoniya-89] M. S. Milyukova (1965). Analytical chemistry of plutonium. Moscow: Nauka. ISBN 0-250-39918-0.

[m25-90] Myasoedov, pp. 25–29

[91] Myasoedov, p. 88

[Tablitsa_soedineniy-92] "Таблица Inorganic and Coordination compounds" (in Russian). http://chemanalytica.com/book/novyy_spravochnik_khimika_i_tekhnologa/01_osnovnye_svoystva_neorganicheskikh_organicheskikh_i_elementoorganicheskikh_soedineniy. Retrieved 11 July 2010.

[93] According to other sources, cubic sesquioxide of curium is olive-green. See "Соединения curium site XuMuK.ru" (in Russian). Archived from the original on 18 August 2010. http://www.xumuk.ru/encyklopedia/2248.html. Retrieved 11 July 2010.

[94] The atmosphere during the synthesis affects the lattice parameters, which might be due to non-stoichiometry as a result of oxidation or reduction of the trivalent californium. Main form is the cubic oxide of californium(III).

[g1268-95] Greenwood, p. 1268

[96] L.R. Morss, Norman M. Edelstein and Jean Fuger (2011). The Chemistry of the Actinide and Transactinide Elements (Set Vol.1–6). Springer. pp. 2139–. ISBN 978-94-007-0210-3. http://books.google.com/books?id=9vPuV3A0UGUC&pg=PA2139.

[g1270-97] Greenwood, p. 1270

[98] Myasoedov, pp. 96–99

[99] Nave, S.; Haire, R.; Huray, Paul (1983). "Magnetic properties of actinide elements having the 5f⁶ and 5f⁷ electronic configurations". Physical Review B 28: 2317. Bibcode 1983PhRvB..28.2317N. doi:10.1103/PhysRevB.28.2317.

[g1269-100] Greenwood, p.1269

[101] Smoke Detectors and Americium, Nuclear Issues Briefing Paper 35, May 2002

[g1262-102] Greenwood, p. 1262

[g220-103] Golub, pp. 220–221

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[105] Greenwood, pp. 1256–1261

[106] Sergey Popov, Alexander Sergeev (2008). "Universal Alchemy" (in Russian). Vokrug Sveta 2811 (4). http://www.vokrugsveta.ru/vs/article/6214/.

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[yield-108] John Malik (September 1985). The Yields of the Hiroshima and Nagasaki Explosions. Los Alamos. p. Table VI. LA-8819. Archived from the original on 24 February 2009. http://www.fas.org/sgp/othergov/doe/lanl/docs1/00313791.pdf. Retrieved 15 February 2009.

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[110] John Holdren and Matthew Bunn Nuclear Weapons Design & Materials. Project on Managing the Atom (MTA) for NTI. 25 November 2002

[111] Apollo 14 Press Kit – 01/11/71, NASA, pp. 38–39

[burakov-112] B.E. Burakov, M.I Ojovan, W.E. Lee (2010). Crystalline Materials for Actinide Immobilisation. World Scientific. ISBN 1848164181. http://books.google.com/books?id=BWriuXxa7CYC&printsec=frontcover.

[113] M. I. Ojovan, W.E. Lee (2005). An Introduction to Nuclear Waste Immobilisation. Amsterdam: Elsevier. ISBN 0080444628. http://books.google.com/books?id=vQkQnmo_bE0C&printsec=frontcover.

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