Fermium

properties
[ Rn ] 5 f 12 7 s 2 100 m Periodic table
General
Name , symbol , atomic number	Fermium, Fm, 100
Element category	Actinoids
Group , period , block	Ac , 7 , f
CAS number	7440-72-4
Atomic
Atomic mass	257,0951 u
Atomic radius (calculated)	- (equivalent: 198) pm
Electron configuration	[ Rn ] 5 f 12 7 s 2
1. Ionization energy	6th.50 (7) eV ≈ 627 kJ / mol
2. Ionization energy	12.4 (4) eV ≈ 1 200kJ / mol
3. Ionization energy	23.2 (4) eV ≈ 2 240 kJ / mol
4. Ionization energy	39.3 (4) eV ≈ 3 790 kJ / mol
5. Ionization energy	55.0 (1.9) eV ≈ 5 310 kJ / mol
Physically
Physical state	firmly
Melting point	(calculated) 1125 K (approx. 852 ° C)
Chemically
Oxidation states	+2, +3
Normal potential	−1.96  V (Fm 3+ + 3 e - → Fm) −2.37  V (Fm 2+ + 2 e - → Fm)
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP 250 m {syn.} 1.8 · 10 3  s (30 min) α (> 90%) 247 Cf ε (<10%) 251 it 251 ft {syn.} 19 · 10 3  s (5.3 h ) ε (98.20%) 1.474 251 it α (1.80%) 7.425 247 Cf 252 ft {syn.} 105.8 · 10 3  s (25.39 h ) α (≈ 100%) 7.153 248 Cf SF (0.0023%) ? ? 253 m {syn.} ≈260 · 10 3  s (3.00 d ) ε (88%) 0.333 253 it α (12%) 7.197 249 Cf 254 m {syn.} 11.7 · 10 3  s (3.240 h) α (≈ 100%) 7.037 250 cf SF (0.0592%) ? ? 255 ft {syn.} 72.25 · 10 3  s (20.07 h) α (100%) 7.451 251 Cf SF  (2.4 · 10 −5  %) ? ? 256 ft {syn.} 9.456 · 10 3  s (157.6 min) SF (91.9%) ? ? α (8.1%) 7.027 252 Cf 257 m {syn.} approx. 8.68 10 6  s (100.5 d) α (≈ 100%) 6.864 253 Cf SF (0.210%) ? ? 258 ft {syn.} 0.37 10 −3  s (370 μs ) SF (≈ 100%) ? ? 259 m {syn.} 1.5 s SF (100%) ? ?
For other isotopes see list of isotopes
Hazard and safety information
Radioactive
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Fermium is an exclusively artificially produced chemical element with the element symbol Fm and the atomic number 100. In the periodic table it is in the group of actinides ( 7th period , f-block ) and is also one of the transuranic elements . Fermium is a radioactive metal, which, however, has not yet been represented as a metal due to the small quantities available. It was discovered in 1952 after the test of the first American hydrogen bomb and named in honor of Enrico Fermi , who, however, had nothing to do with the discovery of or research on fermium.

history

Fermium was discovered by Ivy Mike after the explosion .

Elution curves :
chromatographic separation of Fm (100), Es (99), Cf, Bk, Cm, Am.

Namesake Enrico Fermi in the 1940s

Fermium was found along with Einsteinium after testing the first American hydrogen bomb, Ivy Mike , on November 1, 1952 on the Eniwetok Atoll . The first samples were obtained on filter papers that were carried when flying through the explosion cloud. Larger amounts were later isolated from corals. For reasons of military secrecy, the results were initially not published.

A first investigation of the remains of the explosion had shown the formation of a new plutonium isotope ²⁴⁴ Pu, which could only have resulted from the uptake of six neutrons by a uranium- 238 core and two subsequent β-decays .

${\displaystyle \mathrm {^{238}_{\ 92}U\ {\xrightarrow[{-2\ \beta ^{-}}]{+\ 6\ (n,\gamma )}}\ _{\ 94}^{244}Pu} }$

At the time, it was believed that the absorption of neutrons by a heavy nucleus was a rare occurrence. However, the identification of ²⁴⁴ Pu led to the conclusion that uranium nuclei can capture many neutrons, resulting in new elements.

The formation was achieved through continued neutron capture : At the moment of detonation, the neutron flux density was so high that most of the - radioactive - atomic nuclei that had formed in the meantime had not yet decayed by the next neutron capture. With a very high neutron flux, the mass number increases sharply without the atomic number changing. Only then do the resulting unstable nuclides decay over many β-decays to stable or unstable nuclides with a high atomic number:

${\displaystyle \mathrm {^{238}_{\ 92}U\ {\xrightarrow[{-8\ \beta ^{-}}]{+\ 15,\ 16,\ 17\ (n,\gamma )}}\ _{\ \ \ \ \ \ \ \ \ \ 100}^{253,\ 254,\ 255}Fm} }$

The discovery of fermium ( Z  = 100) required more material as it was believed that the yield would be at least an order of magnitude lower than that of element 99. Therefore, contaminated corals from Eniwetok Atoll (where the test had taken place) were taken to the University of California Radiation Laboratory in Berkeley, California for processing and analysis. The dissolved actinide ions were separated in the presence of a citric acid / ammonium citrate buffer in a weakly acidic medium ( pH  ≈ 3.5) with ion exchangers at an elevated temperature. About two months later, a new component was isolated, a high-energy α-emitter (7.1 MeV) with a half-life of about one day. With such a short half-life, it could only arise from the β-decay of an Einsteinium isotope, and so an isotope of element 100 had to be the new one: it was quickly identified as ²⁵⁵ Fm (t _½  = 20.07 hours).

In September 1953, there was no telling when the results of the teams in Berkeley , Argonne and Los Alamos would be published. It was decided to produce the new elements through bombardment experiments; At the same time, it was assured that these results would not fall under secrecy and could therefore be published. Einsteinium isotopes were produced shortly afterwards at the University of California Radiation Laboratory by bombarding uranium ( ²³⁸ U) with nitrogen ( ¹⁴ N). It was noted that there is research on this element that has so far been kept secret. Isotopes of the two newly discovered elements were generated by irradiating the plutonium isotope ²³⁹ Pu, and the results were published in five publications in quick succession. The final reactions from Californium are:

${\displaystyle \mathrm {^{252}_{\ 98}Cf\ {\xrightarrow {(n,\gamma )}}\ _{\ 98}^{253}Cf\ {\xrightarrow[{17,81\ d}]{\beta ^{-}}}\ _{\ 99}^{253}Es\ {\xrightarrow {(n,\gamma )}}\ _{\ 99}^{254}Es\ {\xrightarrow[{}]{\beta ^{-}}}\ _{100}^{254}Fm} }$

The Berkeley team was also concerned that another group of researchers might discover and publish the lighter isotopes of element 100 by ion bombardment before they could publish their classified research. Because at the end of 1953 and at the beginning of 1954 a working group from the Nobel Institute for Physics in Stockholm fired at uranium nuclei with oxygen nuclei; the isotope with the mass number 250 of the element 100 ( ²⁵⁰ μm) was formed. The unequivocal identification could be obtained from the characteristic energy of the α-particle emitted during the decay .

${\displaystyle \mathrm {^{238}_{\ 92}U\ +\ _{\ 8}^{16}O\ \longrightarrow \ _{100}^{250}Fm\ +\ 4\ _{0}^{1}n} }$      ${\displaystyle \mathrm {(_{100}^{250}Fm\ \longrightarrow \ _{\ 98}^{246}Cf\ +\ _{2}^{4}He)} }$

The Berkeley team has already published some results on the chemical properties of both elements. Finally, the results of the thermonuclear explosion were released in 1955 and then published.

Ultimately, the Berkeley team's priority was universally recognized, as their five publications preceded the Swedish publication and they could rely on the previously secret results of the 1952 thermonuclear explosion. This was associated with the privilege of naming the new elements. They decided to name them after famous scientists who had already died. It was quickly agreed to give the names in honor of Albert Einstein and Enrico Fermi , both of whom had recently died: “We suggest for the name for the element with the atomic number 99, einsteinium (symbol E) after Albert Einstein and for the name for the element with atomic number 100, fermium (symbol Fm), after Enrico Fermi. "The announcement for the two newly discovered elements Einsteinium and Fermium was made by Albert Ghiorso at the 1st Geneva Atomic Conference , which took place from 8 to Took place on August 20, 1955.

The element was later given the systematic name Unnilnilium for a time.

Isotopes

All 19 nuclides and 3 nuclear isomers known to date are radioactive and unstable. The known mass numbers range from 242 to 260. The isotope ²⁵⁷ Fm has by far the longest half-life with 100.5 days, so that there can be no more natural occurrences on earth. ²⁵³ Fm has a half-life of 3 days, ²⁵¹ Fm of 5.3 hours, ²⁵² Fm of 25.4 hours, ²⁵⁴ Fm of 3.2 hours, ²⁵⁵ Fm of 20.1 hours and ²⁵⁶ Fm of 2.6 hours. All the others have half-lives of 30 minutes to less than a millisecond.

If one takes out the decay of the longest-lived isotope ²⁵⁷ Fm, then first ²⁵³ Cf arises through α-decay , which in turn changes into ²⁵³ Es through β-decay . The further decay then leads via ²⁴⁹ Bk, ²⁴⁹ Cf, ²⁴⁵ Cm, ²⁴³ Am, ²⁴¹ Pu, ²⁴¹ Am to ²³⁷ Np, the beginning of the neptunium series (4 n + 1).

${\displaystyle \mathrm {^{257}_{100}Fm\ {\xrightarrow[{100,5\ d}]{\alpha }}\ _{\ 98}^{253}Cf\ {\xrightarrow[{17,81\ d}]{\beta ^{-}}}\ _{\ 99}^{253}Es\ {\xrightarrow[{20,47\ d}]{\alpha }}\ _{\ 97}^{249}Bk\rightarrow \ ...\rightarrow \ _{\ 93}^{237}Np} }$

The times given are half-lives.

The decay from Fermium-257 to the Neptunium series .

See also : List of Fermium Isotopes

Fermium barrier

The fermium barrier is the fact that the fermium isotopes ²⁵⁸ Fm, ²⁵⁹ Fm and ²⁶⁰ Fm sometimes disintegrate spontaneously after just a fraction of a second (t _½  = 370  µs , 1.5 s or 4 ms). ²⁵⁷ Fm is an α-emitter and breaks down to ²⁵³ Cf. In addition, none of the previously known fermium isotopes shows β-decays, which prevents the formation of mendelevium by decay from fermium. These facts prevent practically any effort to produce elements with atomic numbers over 100 or mass numbers greater than 257 with the help of neutron radiation, for example with the help of a nuclear reactor. Fermium is thus the last element that can be produced by neutron capture. Any attempt to add more neutrons to a fermium nucleus leads to spontaneous fission.

Extraction

Fermium is produced by bombarding lighter actinides with neutrons in a nuclear reactor. The main source is the 85  MW high-flux isotope reactor at Oak Ridge National Laboratory in Tennessee, USA, which is set up for the production of transcurium elements (Z> 96).

In Oak Ridge larger amounts are to Curium been irradiated to decigram quantities of Californium , milligram quantities of berkelium and einsteinium and picogram to produce quantities of fermium. Nanogram and microgram quantities of fermium can be prepared for specific experiments. The amounts of fermium produced in thermonuclear explosions of 20 to 200 kilotons are believed to be on the order of a few milligrams, although it is mixed with a huge amount of explosion debris; 40 picograms of ²⁵⁷ Fm were isolated from 10 kilograms of the remains of the explosion from the Hutch test on July 16, 1969.

After irradiation, fermium must be separated from the other actinides and the lanthanoid fission products. This is usually achieved by ion exchange chromatography , the standard procedure runs with cation exchangers such as Dowex 50 or T EVA , elution is carried out with a solution of ammonium α-hydroxyisobutyrate . Smaller cations form more stable complexes with the methyl α-hydroxyisobutyrate anions, so they are preferentially eluted from the column. A rapid fractional crystallization method has also been described.

Although the most stable isotope of fermium is ²⁵⁷ Fm with a half-life of 100.5 days, most studies are based on ²⁵⁵ Fm (t _½  = 20.07 hours). This isotope can easily be isolated; it is a decay product of the ²⁵⁵ Es (t _½  = 39.8 days).

Small amounts of einsteinium and fermium were isolated and separated from plutonium , which was irradiated with neutrons. Four Einsteinium isotopes were found (with details of the half-lives measured at that time): ²⁵³ Es (α-emitters with t _½  = 20.03 days, as well as with a spontaneous fission half-life of 7 × 10 ⁵  years); ^{254 m} Es (β-emitters with t _½  = 38.5 hours), ²⁵⁴ Es (α-emitters with t _½  = ∼ 320 days) and ²⁵⁵ Es (β-emitters with t _½  = 24 days). Two fermium isotopes were found: ²⁵⁴ Fm (α-emitters with t _½  = 3.24 hours, as well as with a spontaneous fission half-life of 246 days) and ²⁵⁵ Fm (α-emitters with t _½  = 21.5 hours).

Bombarding uranium with five-fold ionized nitrogen and six-fold ionized oxygen atoms also produced Einsteinium and Fermium isotopes.

properties

Fermium-ytterbium alloy

In the periodic table , the fermium with atomic number 100 is in the series of actinides, its predecessor is the Einsteinium, the following element is the Mendelevium . Its analogue in the lanthanide series is erbium .

Physical Properties

The metal has not yet been shown, but measurements have been made on alloys with lanthanoids , and some calculations or predictions are available. The enthalpy of sublimation is directly related to the valence electron structure of the metal. The sublimation enthalpy of fermium was determined directly by measuring the partial pressure of the fermium using Fm- Sm and Fm / Es- Yb alloys in the temperature range from 642 to 905 K. They arrived at a value of 142 (13) kJ mol ⁻¹ . Since the sublimation enthalpy of fermium is similar to that of the divalent einsteinium, europium and ytterbium, it was concluded that fermium has a divalent metallic state. Comparisons with radii and melting points of europium, ytterbium and einsteinium metals resulted in estimated values ​​of 198  pm and 1125 K for fermium.

The normal potential was estimated to be similar to the ytterbium Yb ³⁺ / Yb ²⁺ pair, i.e. about −1.15 V in relation to the standard hydrogen electrode , a value that agrees with theoretical calculations. On the basis of polarographic measurements, a normal potential of −2.37 V was determined for the Fm ²⁺ / Fm ⁰ pair. Fm ³⁺ can be reduced to Fm ²⁺ relatively easily , e.g. B. with samarium (II) chloride , precipitates together with the fermium.

Chemical properties

Until now, the chemistry of the fermium could only be investigated in solution with the help of tracer techniques; fixed connections were not established. Under normal conditions, fermium is in solution as an Fm ³⁺ ion, which has a hydration number of 16.9 and an acid constant of 1.6 · 10 ⁻⁴ (pK _s  = 3.8). Fm ³⁺ forms complexes with a variety of organic ligands with hard donor atoms such as oxygen; and these complexes are usually more stable than those of the preceding actinides. It also forms anionic complexes with ligands such as chloride or nitrate; and these complexes also appear to be more stable than those of Einsteinium or Californium. It is assumed that the bond in the complexes of the higher actinides mostly has an ionic character: the Fm ³⁺ ion is, as expected, smaller than the previous An ³⁺ ions - due to the higher effective nuclear charge of fermium; and with that, fermium would likely form shorter and stronger metal-ligand bonds.

safety instructions

Classifications according to the CLP regulation are not available because they only include chemical hazard and play a completely subordinate role compared to the hazards based on radioactivity . The latter also only applies if the amount of substance involved is relevant.

use

Fermium - in the form of its compounds in solution - is primarily obtained in small quantities for study purposes. Compounds of the fermium have not yet been shown in solid form.

literature

• Robert J. Silva: Fermium, Mendelevium, Nobelium, and Lawrencium , in: Lester R. Morss, Norman M. Edelstein, Jean Fuger (Eds.): The Chemistry of the Actinide and Transactinide Elements , Springer, Dordrecht 2006; ISBN 1-4020-3555-1 , pp. 1621-1651 ( doi: 10.1007 / 1-4020-3598-5_13 ).
• Glenn T. Seaborg (Ed.): Proceedings of the Symposium Commemorating the 25th Anniversary of Elements 99 and 100 , January 23, 1978; Report LBL-7701, April 1979.
• Gmelin's Handbook of Inorganic Chemistry , System No. 71, Transurans: Part A 1 II, pp. 19-20; Part A 2, p. 47; Part B 1, p. 84.

Web links

Commons : Fermium  - collection of images, videos and audio files

Wiktionary: Fermium  - explanations of meanings, word origins, synonyms, translations

• Entry on fermium. In: Römpp Online . Georg Thieme Verlag, accessed on January 3, 2015.
• Albert Ghiorso: Einsteinium and Fermium , Chemical & Engineering News, 2003.

Individual evidence

1. ↑ The values ​​of the atomic and physical properties (infobox) are, unless otherwise stated, taken from: Robert J. Silva: Fermium, Mendelevium, Nobelium, and Lawrencium , in: Lester R. Morss, Norman M. Edelstein, Jean Fuger ( Ed.): The Chemistry of the Actinide and Transactinide Elements , Springer, Dordrecht 2006; ISBN 1-4020-3555-1 , pp. 1621-1651.
2. ↑ ^{a b c d e} Entry on fermium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
3. ↑ ^{a b c d e} Entry on fermium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
4. ↑ The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling. With regard to other hazards, this element has either not yet been classified or a reliable and citable source has not yet been found.
5. ↑ ^{a b c d e f g h} Albert Ghiorso: Einsteinium and Fermium , Chemical & Engineering News, 2003.
6. ↑ Albert Ghiorso , G. Bernard Rossi, Bernard G. Harvey, Stanley G. Thompson: Reactions of U ²³⁸ with Cyclotron-Produced Nitrogen Ions , in: Physical Review , 1954 , 93  (1), pp. 257-257 ( doi: 10.1103 / PhysRev.93.257 ).
7. ↑ SG Thompson, A. Ghiorso, BG Harvey, GR Choppin: Transcurium Isotopes Produced in the Neutron Irradiation of Plutonium , in: Physical Review , 1954 , 93  (4), pp. 908-908 ( doi: 10.1103 / PhysRev.93.908 ) .
8. ↑ BG Harvey, SG Thompson, A. Ghiorso, GR Choppin: Further Production of Transcurium Nuclides by Neutron Irradiation , in: Physical Review , 1954 , 93  (5), pp. 1129-1129 ( doi: 10.1103 / PhysRev.93.1129 ).
9. ↑ MH Studier, PR Fields, H. Diamond, JF Mech, AM Friedman, PA Sellers, G. Pyle, CM Stevens, LB Magnusson, JR Huizenga: Elements 99 and 100 from Pile-Irradiated Plutonium , in: Physical Review , 1954 , 93  (6), pp. 1428-1428 ( doi: 10.1103 / PhysRev.93.1428 ).
10. ↑ PR Fields, MH Studier, JF Mech, H. Diamond, AM Friedman, LB Magnusson, JR Huizenga: Additional Properties of Isotopes of Elements 99 and 100 , in: Physical Review , 1954 , 94  (1), pp. 209-210 ( doi: 10.1103 / PhysRev.94.209 ).
11. ↑ GR Choppin, SG Thompson, A. Ghiorso, BG Harvey: Nuclear Properties of Some Isotopes of Californium, Elements 99 and 100 , in: Physical Review , 1954 , 94  (4), pp. 1080-1081 ( doi: 10.1103 / PhysRev .94.1080 ).
12. ↑ Hugo Atterling, Wilhelm Forsling, Lennart W. Holm, Lars Melander, Björn Åström: Element 100 Produced by Means of Cyclotron-Accelerated Oxygen Ions , in: Physical Review , 1954 , 95  (2), pp. 585-586 ( doi: 10.1103 / PhysRev.95.585.2 ).
13. ↑ ^{a b} G. T. Seaborg , SG Thompson, BG Harvey, GR Choppin: Chemical Properties of Elements 99 and 100 ; Abstract ; Machine script (July 23, 1954), Radiation Laboratory, University of California, Berkeley, UCRL-2591 (Rev.) (PDF; 1.5 MB).
14. ^ ^{A b} S. G. Thompson, BG Harvey, GR Choppin, GT Seaborg: Chemical Properties of Elements 99 and 100 , in: J. Am. Chem. Soc. , 1954 , 76  (24), pp. 6229-6236 ( doi: 10.1021 / ja01653a004 ).
15. ^ ^{A b} A. Ghiorso, SG Thompson, GH Higgins, GT Seaborg ( Radiation Laboratory and Department of Chemistry, University of California, Berkeley, California ), MH Studier, PR Fields, SM Fried, H. Diamond, JF Mech, GL Pyle , JR Huizenga, A. Hirsch, WM Manning ( Argonne National Laboratory, Lemont, Illinois ), CI Browne, HL Smith, RW Spence ( Los Alamos Scientific Laboratory, Los Alamos, New Mexico ): New Elements Einsteinium and Fermium, Atomic Numbers 99 and 100 , in: Physical Review , 1955 , 99  (3), pp. 1048-1049 ( doi: 10.1103 / PhysRev.99.1048 ; Maschinoscript (June 9, 1955), Lawrence Berkeley National Laboratory. Paper UCRL-3036 ).
16. ^ PR Fields, MH Studier, H. Diamond, JF Mech, MG Inghram, GL Pyle, CM Stevens, S. Fried, WM Manning ( Argonne National Laboratory, Lemont, Illinois ); A. Ghiorso, SG Thompson, GH Higgins, GT Seaborg ( University of California, Berkeley, California ): Transplutonium Elements in Thermonuclear Test Debris , in: Physical Review , 1956 , 102  (1), pp. 180-182 ( doi: 10.1103 /PhysRev.102.180 ).
17. ↑ David R. Lide: CRC Handbook of Chemistry and Physics , 85th Edition, CRC Press, 2004, ISBN 978-0-8493-0485-9 , Section 4, pp. 4–10 ( limited preview in Google Book Search) . This is no longer mentioned in the 90th edition (pp. 4–12 to 4–13).
18. ↑ G. Pfennig, H. Klewe-Nebenius, W. Seelmann-Eggebert (eds.): Karlsruher Nuklidkarte , 7th edition, 2006.
19. ^ ^{A b} G. Audi, O. Bersillon, J. Blachot, AH Wapstra: The NUBASE evaluation of nuclear and decay properties , in: Nuclear Physics A , 729, 2003, pp. 3–128. doi : 10.1016 / j.nuclphysa.2003.11.001 . ( PDF ; 1.0 MB).
20. ↑ ^{a b c d e f} Robert J. Silva: Fermium, Mendelevium, Nobelium, and Lawrencium , in: Lester R. Morss, Norman M. Edelstein, Jean Fuger (Ed.): The Chemistry of the Actinide and Transactinide Elements , 3 3rd edition, Springer, Dordrecht 2006, Volume 3, pp. 1621-1651.
21. ^ High Flux Isotope Reactor , Oak Ridge National Laboratory; Retrieved September 23, 2010.
22. ↑ ^{a b} C. E. Porter, FD Riley, Jr., RD ​​Vandergrift, LK Felker: Fermium Purification Using Teva ™ Resin Extraction Chromatography , in: Sep. Sci. Technol. , 1997 , 32  (1-4), pp. 83-92 ( doi: 10.1080 / 01496399708003188 ).
23. ↑ M. Sewtz, H. Backe, A. Dretzke, G. Kube, W. Lauth, P. Schwamb, K. Eberhardt, C. Grüning, P. Thörle, N. Trautmann, P. Kunz, J. Lassen, G . Passler, CZ Dong, S. Fritzsche, RG Haire: First Observation of Atomic Levels for the Element Fermium ( Z  = 100) , in: Phys. Rev. Lett. , 2003 , 90  (16), p. 163002 ( doi: 10.1103 / PhysRevLett.90.163002 ).
24. ↑ RW Hoff, EK Hulet: Engineering with Nuclear Explosives , 1970 , 2 , pp. 1283-1294.
25. ^ GR Choppin, BG Harvey, SG Thompson: A new eluant for the separation of the actinide elements , in: J. Inorg. Nucl. Chem. , 1956 , 2  (1), pp. 66-68 ( doi: 10.1016 / 0022-1902 (56) 80105-X ).
26. ↑ NB Mikheev, AN Kamenskaya, NA Konovalova, IA Rumer, SA Kulyukhin: High-speed method for the separation of fermium from actinides and lanthanides , in: Radiokhimiya , 1983 , 25  (2), pp. 158-161.
27. ↑ M. Jones, RP Schuman, JP Butler, G. Cowper, TA Eastwood, HG Jackson: Isotopes of Einsteinium and Fermium Produced by Neutron Irradiation of Plutonium , in: Physical Review , 1956 , 102  (1), pp. 203-207 ( doi: 10.1103 / PhysRev.102.203 ).
28. ↑ LI Guseva, KV Filippova, Yu. B. Gerlit, VA Druin, BF Myasoedov, NI Tarantin: Experiments on the Production of Einsteinium and Fermium with a Cyclotron , in: Journal of Nuclear Energy , 1954 , 3  (4), pp. 341–346 (translated in November 1956) ( doi: 10.1016 / 0891-3919 (56) 90064-X ).
29. ↑ NB Mikheev, VI Spitsyn, AN Kamenskaya, NA Konovalova, IA Rumer, LN Auerman, AM Podorozhnyi: Determination of oxidation potential of the pair Fm ²⁺ / Fm ³⁺ , in: Inorg. Nucl. Chem. Lett. , 1977 , 13  (12), pp. 651-656 ( doi: 10.1016 / 0020-1650 (77) 80074-3 ).
30. ^ LJ Nugent, in: MTP Int. Rev. Sci .: Inorg. Chem., Ser. One , 1975 , 7 , pp. 195-219.
31. ↑ K. Samhoun, F. David, RL Hahn, GD O'Kelley, JR Tarrant, DE Hobart: Electrochemical study of mendelevium in aqueous solution: No evidence for monovalent ions , in: J. Inorg. Nucl. Chem. , 1979 , 41  (12), pp. 1749-1754 ( doi: 10.1016 / 0022-1902 (79) 80117-7 ).
32. ↑ Jaromír Malý: The amalgamation behavior of heavy elements 1. Observation of anomalous preference in formation of amalgams of californium, einsteinium, and fermium , in: Inorg. Nucl. Chem. Lett. , 1967 , 3  (9), pp. 373-381 ( doi: 10.1016 / 0020-1650 (67) 80046-1 ).
33. ↑ NB Mikheev, VI Spitsyn, AN Kamenskaya, BA Gvozdec, VA Druin, IA Rumer, RA Dyachkova, NA Rozenkevitch, LN Auerman: Reduction of fermium to divalent state in chloride aqueous ethanolic solutions , in: Inorg. Nucl. Chem. Lett. , 1972 , 8  (11), pp. 929-936 ( doi: 10.1016 / 0020-1650 (72) 80202-2 ).
34. ↑ EK Hulet, RW Lougheed, PA Baisden, JH Landrum, JF Wild, RF Lundqvist: Non-observance of monovalent Md , in: J. Inorg. Nucl. Chem. , 1979 , 41  (12), pp. 1743-1747 ( doi: 10.1016 / 0022-1902 (79) 80116-5 ).
35. ^ Robert Lundqvist, EK Hulet, TA Baisden: Electromigration Method in Tracer Studies of Complex Chemistry. II. Hydrated Radii and Hydration Numbers of Trivalent Actinides , in: Acta Chem. Scand., Ser. A , 1981 , 35 , pp. 653-661 ( doi: 10.3891 / acta.chem.scand.35a-0653 ).
36. ↑ H. Hussonnois, S. Hubert, L. Aubin, R. Guillaumont, G. Boussieres: Radiochem. Radioanal. Lett. , 1972 , 10 , pp. 231-238.

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