Skip to Main Content

About Fermium

Fermium Bohr

Fermium was discovered in 1952 by a team of Berkeley researchers led by Albert Ghiorso while analyzing coral contaminated by the top-secret Ivy Mike nuclear test, of but their discovery was kept secret until 1955 because of Cold War tensions. Fermium was named for the recently deceased Enrico Fermi and his invaluable contributions to the field of nuclear physics.

Little is known about the properties of fermium because only tiny amounts have ever been produced; after their initial experiement, Ghiorso's team was again successful in producing both fermium and einsteinium via the bombardment of plutonium-239. It is a highly radioactive transuranic actinide with a very short half-life. There are no uses for it outside of scientific research.

Fermium Properties

Fermium Bohr ModelFermium is a Block F, Group 3, Period 7 element. The number of electrons in each of fermium's shells is 2, 8, 18, 32, 30, 8, 2 and its electron configuration is [Rn] 5f12 7s2. The fermium atom has a Van der Waals radius of 245 pm. In its elemental form, fermium's CAS number is 7440-72-4. Fermium is a synthetic element that is produced by the bombardment of lighter actinides with neutrons in a nuclear reactor. Fermium was discovered at the Lawrence Berkeley National Laboratory in 1952. It was named after Enrico Fermi, Professor of Theoretical Physics at the University of Rome. Fermi was a Nobel Prize winner whose work lead to the discovery of slow neutrons which then resulted in the discovery of nuclear fission and the production of elements lying beyond those included on the periodic table of 1938. Fermium was the eighth transuranic element of the actinide series to be discovered.

Fermium information, including technical data, safety data and its properties, research, applications and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity and thermal properties are included.

Symbol: Fm
Atomic Number: 100
Atomic Weight: 257
Element Category: Actinide
Group, Period, Block: n/a, 7, f
Color: unknown (presumably metallic/ silvery white/ gray)
Other Names: Fermio
Melting Point: 1527 °C, 2780.6 °F, 1800.15 K
Boiling Point: N/A
Density: N/A
Liquid Density @ Melting Point: N/A
Density @ 20°C: 8.84 g/cm3
Density of Solid: N/A
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): N/A
Heat of Vaporization (kJ·mol-1): N/A
Heat of Atomization (kJ·mol-1): 141
Thermal Conductivity: N/A
Thermal Expansion: N/A
Electrical Resistivity: N/A
Tensile Strength: N/A
Molar Heat Capacity: N/A
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: N/A
Pauling Electronegativity: 1.3
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.2
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.7
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 100
Protons: 100
Neutrons: 157
Electron Configuration: [Rn] 5f12 7s2
Atomic Radius: N/A
Atomic Radius,
non-bonded (Å):
Covalent Radius: N/A
Covalent Radius (Å): 1.67
Van der Waals Radius: 245 pm
Oxidation States: 2, 3
Phase: Solid
Crystal Structure: N/A
Magnetic Ordering: N/A
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 627 kJ·mol-1 (estimated)
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 7440-72-4
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [Fm]
InChI Identifier: InChI=1S/Fm
PubChem CID: 23998
ChemSpider ID: 22434
Earth - Total: N/A
Mercury - Total: N/A
Venus - Total: N/A
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: N/A
Earth -  Crust (Crustal Rocks), ppb by atoms: N/A
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Lawrence Berkeley Nat'l Laboratory
Discovery Date: 1952
First Isolation: N/A

Fermium Isotopes

Fermium is an artificial element. It has no stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
241Fm 241.07421(32)# 730(60) µs SF; α to 237Cf 5/2#+ N/A N/A -
242Fm 242.07343(43)# 0.8(2) ms SF; α to 238Cf 0+ N/A 1806.625 -
243Fm 243.07447(23)# 231(9) ms α to 239Cf; SF; β+to 243Es 7/2-# N/A 1813.69104 -
244Fm 244.07404(22)# 3.12(8) ms α to 240Cf; β+to 244Es; SF 0+ N/A 1822.165039 -
245Fm 245.07535(21)# 4.2(13) s α to 241Cf; β+to 245Es; SF 1/2+# N/A 1829.026978 -
246Fm 246.075350(17) 1.54(4) s α to 242Cf; β+to 246Es; SF 0+ N/A 1837.185669 -
247Fm 247.07695(12)# 31(1) s α to 243Cf; β+to 247Es (7/2+) N/A 1843.824951 -
248Fm 248.077186(9) 35.1(8) s β+to 248Es; α to 244Cf; SF 0+ N/A 1851.555908 -
249Fm 249.078928(7) 1.6(1) min β+to 249Es; α to 245Cf; SF (7/2+)# N/A 1857.912964 -
250Fm 250.079521(9) 30.4(15) min α to 246Cf; EC to 250Es; SF 0+ N/A 1865.527832 -
251Fm 251.081540(16) 5.30(8) h EC to 251Es; α to 247Cf (9/2-) N/A 1871.687988 -
252Fm 252.082467(6) 25.39(4) h α to 248Cf; SF 0+ N/A 1878.927002 -
253Fm 253.085185(4) 3.00(12) d EC to 253Es; α to 249Cf (1/2)+ N/A 1884.46814 -
254Fm 254.0868544(30) 3.240(2) h α to 250Cf; SF 0+ N/A 1890.982422 -
255Fm 255.089964(5) 20.07(7) h α to 251Cf; SF 7/2+ N/A 1896.159058 -
256Fm 256.091774(8) 157.6(13) min α to 252Cf; SF 0+ N/A 1902.543335 -
257Fm 257.095106(7) 100.5(2) d α to 253Cf; SF (9/2+) N/A 1907.510864 -
258Fm 258.09708(22)# 370(14) µs SF 0+ N/A 1913.746948 -
259Fm 259.1006(3)# 1.5(3) s SF 3/2+# N/A 1918.540039 -
260Fm 260.10281(55)# 1# min N/A 0+ N/A N/A -
Fermium Elemental Symbol

Recent Research & Development for Fermium

  • M. Sewtz, H. Backe, C.Z. Dong, A. Dretzke, K. Eberhardt, S. Fritzsche, C. Grüning, R.G. Haire, G. Kube, P. Kunz, J. Lassen, W. Lauth, G. Passler, P. Schwamb, P. Thörle, N. Trautmann, Resonance ionization spectroscopy of fermium (Z=100), Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 58, Issue 6, 30 June 2003
  • Stefan Cwiok, Piotr Rozmej, Adam Sobiczewski, Zygmunt Patyk, Two fission modes of the heavy fermium isotopes, Nuclear Physics A, Volume 491, Issue 2, 9 January 1989
  • Metabolic data for fermium, Annals of the ICRP, Volume 19, Issue 4, 1988
  • Fermium, Annals of the ICRP, Volumes 11–13, Part 2, 1983
  • Fermium, Annals of the ICRP, Volume 8, Issues 1–3, 1982
  • Metabolic data for fermium, Annals of the ICRP, Volume 6, Issues 2–3, 1981
  • B. Fricke, G. Soff, Dirac-Fock-Slater calculations for the elements Z = 100, fermium, to Z = 173, Atomic Data and Nuclear Data Tables, Volume 19, Issue 1, January 1977
  • F. Go¨nnenwein, H. Schultheis, R. Schultheis, K. Wildermuth, Substructure effects in the fission of fermium, Physics Letters B, Volume 57, Issue 4, 21 July 1975
  • Yu.Ts. Oganessian, A.S. Iljinov, A.G. Demin, S.P. Tretyakova, Experiments on the production of fermium neutron-deficient isotopes and new possibilities of synthesizing elements with Z > 100, Nuclear Physics A, Volume 239, Issue 2, 24 February 1975
  • S. Hubert, M. Hussonnois, L. Brillard, G. Goby, R. Guillaumont, Determination simultanee de constantes de formation de complexes citrique de l'Americium, du curium, du Californium, de l'Einsteinium et du fermium, Journal of Inorganic and Nuclear Chemistry, Volume 36, Issue 10, October 1974
  • J.F. Wild, E.K. Hulet, R.W. Lougheed, Some nuclear properties of fermium-257, Journal of Inorganic and Nuclear Chemistry, Volume 35, Issue 4, April 1973