fermium

fermium
Name	Fermium
Atomic number	100
Category	Actinide
Appearance	Unknown (silvery)
Atomic mass	(257)
Phase	Solid (predicted)
Density	~9.7 g/cm3 (predicted)
Melting point	Unknown (~1527 °C predicted)
Boiling point	Unknown
Electron configuration	[Rn] 5f12 7s2 (predicted)
Oxidation states	+2, +3
Discoverer	Albert Ghiorso, Stanley Thompson, Glenn Seaborg
Discovery location	Lawrence Berkeley National Laboratory
Discovery year	1952

fermium is a synthetic, radioactive element with atomic number 100, classified among the actinide series and named after the physicist Enrico Fermi. It was first produced in the aftermath of thermonuclear testing and later synthesized in laboratory facilities; its chemistry resembles later actinides and its isotopes exhibit a range of alpha, beta, and spontaneous fission decay modes. Because fermium is produced in minute quantities and is highly radioactive, research and applications are limited to specialized nuclear, radiochemistry, and materials facilities.

Discovery and Naming

Fermium was discovered in debris from the Ivy Mike thermonuclear test by a team including Albert Ghiorso, Stanley G. Thompson, Kenneth Street Jr., R. D. Macfarlane, and Glenn T. Seaborg, with analyses carried out at University of California, Berkeley and Lawrence Berkeley National Laboratory. The initial identification relied on radiochemical separations and decay-chain correlations linking new nuclides to known isotopes of neptunium, plutonium, and curium recovered from the Pacific test site around Enewetak Atoll. The element was named in honor of Enrico Fermi, noted for contributions to nuclear reactor theory, the Fermi–Dirac statistics development, and roles in the Manhattan Project. The announcement and subsequent laboratory syntheses involved institutions such as Oak Ridge National Laboratory, Los Alamos National Laboratory, and the Argonne National Laboratory, prompting classification and publication discussions during the early Cold War era.

Production and Isolation

Fermium is produced primarily by neutron capture in high-flux neutron environments such as the Ivy Mike test, specialized reactors like the High Flux Isotope Reactor at Oak Ridge, and in heavy-ion accelerators at facilities including the GSI Helmholtz Centre for Heavy Ion Research and Joint Institute for Nuclear Research. Production routes involve multiple neutron captures on heavy actinides (notably uranium and plutonium) to form successive transuranic nuclides including berkelium and californium, followed by beta decays to fermium isotopes. Chemical separation exploits differences with neighboring actinides using ion-exchange columns, solvent extraction, and coprecipitation techniques developed at Lawrence Berkeley National Laboratory and Argonne National Laboratory. Isolations yield microgram to picogram quantities, necessitating handling at facilities such as Los Alamos and national metrology institutes for characterization.

Physical and Chemical Properties

Predicted solid-state and electronic properties of fermium derive from extrapolation within the actinide series and comparisons to holmium and ytterbium analogs; electron configuration models predict a [Rn] 5f12 7s2 ground state with common oxidation states of +3 and +2. Chemical behavior in aqueous solution resembles that of late actinides like californium and einsteinium, with trivalent ions forming complexes with ligands used in coordination chemistry studies at Brookhaven National Laboratory and Stockholm University. Spectroscopic investigations using facilities such as Lawrence Livermore National Laboratory and Institut Laue–Langevin have probed f-electron behavior and covalency in compounds synthesized on microgram scales, including oxychlorides and oxides analogous to plutonium dioxide and neptunium dioxide. Crystallographic data are sparse due to limited sample mass, but theoretical solid-state models and relativistic quantum calculations by groups at Moscow State University and University of California, Berkeley inform predicted lattice parameters and metallic bonding.

Isotopes and Nuclear Decay

More than a dozen fermium isotopes have been characterized, with mass numbers commonly reported in the range A=242–260; notable isotopes include Fm-255, Fm-257, and Fm-259. Isotopes decay via alpha emission, beta decay, and spontaneous fission, with half-lives varying from milliseconds to several hundred days—Fm-257 has a half-life of about 100.5 days. Decay chains link fermium isotopes to daughter nuclides in the transuranic series such as mendelevium, nobelium, and lawrencium, and detection of characteristic alpha energies and fission fragments has been used in identification at facilities like GSI and RIKEN. Nuclear structure studies employ spectrometers at GANIL, TRIUMF, and JINR to measure level schemes, shell effects, and spontaneous-fission fragment distributions, informing models of shell closures near the predicted island of stability discussed by theorists at Oak Ridge and National Superconducting Cyclotron Laboratory.

Applications and Research Uses

Practical applications of fermium are essentially nonexistent outside basic research because of scarcity and radioactivity; research uses focus on nuclear physics, actinide chemistry, and studies of heavy-element electronic structure carried out at institutions such as Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, Brookhaven National Laboratory, and RIKEN. Fermium isotopes have served as targets or tracers in experiments probing neutron-capture pathways relevant to nucleosynthesis studies connected to r-process research in astronomy teams at Max Planck Institute for Astrophysics and Harvard–Smithsonian Center for Astrophysics. Small-scale separations and spectroscopy have aided development of radiochemical techniques used at International Atomic Energy Agency reference labs and informed safety protocols at national nuclear facilities like Idaho National Laboratory.

Safety and Handling

Handling fermium requires specialized hot-cell facilities, alpha- and neutron-shielded gloveboxes, and remote-manipulation equipment at national laboratories including Oak Ridge National Laboratory, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory. Radiological protection practices developed by agencies such as the International Atomic Energy Agency and United States Nuclear Regulatory Commission are applied to limit exposure to alpha particles, gamma radiation, and neutron emissions from spontaneous fission; waste management follows protocols used for transuranic waste at facilities like Waste Isolation Pilot Plant. Transport and custody of fermium samples comply with international agreements overseen by organizations such as the International Maritime Organization and International Civil Aviation Organization when movement is necessary between research centers.

Category:Actinides Category:Synthetic elements Category:Enrico Fermi