Fermium

Fermium (Fm)

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes, most stable is Fm-257 with a half-life of 10 days. First identified by Albert Ghiorso and associates in the debris of the first hydrogen-bomb explosion in 1952.
Atomic Number100
Atomic Weight257
Mass Number241
Group
Period7
Blockf
Protons100 p+
Neutrons141 n0
Electrons100 e-
Fermium-Ytterbium Alloy.jpg Electron shell 100 Fermium.svg Animated Bohr Model of Fm (Fermium) Enhanced Bohr Model of Fm (Fermium) Bohr Model: Fm (Fermium) Orbital Diagram of Fm (Fermium)

Properties

Atomic Radius
Molar Volume
Covalent Radius
167 pm
Metallic Radius
Ionic Radius
110.5 pm
Crystal Radius
124.5 pm
Van der Waals Radius
245 pm
Density
9.7 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy
Heat of Vaporization
Heat of Fusion
Heat of Formation
Electrons
Electron Shells2, 8, 18, 32, 30, 8, 2
Valence Electrons3
Electron Configuration[Rn] 5f12 7s2
Oxidation States2, 3
Electronegativity
Electrophilicity
Phases
PhaseSolid
Gas Phase
Boiling Point
Melting Point
1,800.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Colorless
Appearance
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point
Magnetism
Type
Magnetic Susceptibility (Mass)
Magnetic Susceptibility (Molar)
Magnetic Susceptibility (Volume)
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal Structure ()
Lattice Constant
Lattice Angles
Mechanical Properties
Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
Classification
CategoryActinides, Actinides
CAS Group
IUPAC Group
Glawe Number44
Mendeleev Number36
Pettifor Number37
Geochemical Class
Goldschmidt Classsynthetic
Other
Gas Basicity
Dipole Polarizability
113 ± 20 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section
5,800
Neutron Mass Absorption
Quantum Numbers3H6
Space Group ()

Isotopes of Fermium

Stable Isotopes0
Unstable Isotopes20
Radioactive Isotopes20

241Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
241.074311 ± 0.000322 Da
Mass Number241
G-Factor
Half Life
730 ± 60 us
Spin5/2
Quadrupole Moment
Discovery Year2008
Parity+

241Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)%
α (α emission)14%
β+ (β+ decay; β+ = ϵ + e+)12%

242Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
242.07343 ± 0.00043 Da
Mass Number242
G-Factor
0
Half Life
800 ± 200 us
Spin0
Quadrupole Moment
0
Discovery Year1975
Parity+

242Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)100%
α (α emission)%

243Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
243.074414 ± 0.00014 Da
Mass Number243
G-Factor
Half Life
231 ± 9 ms
Spin7/2
Quadrupole Moment
Discovery Year1981
Parity-

243Fm Decay Modes
Decay ModeIntensity
α (α emission)91%
SF (spontaneous fission)9%
β+ (β+ decay; β+ = ϵ + e+)%

244Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
244.074036 ± 0.000216 Da
Mass Number244
G-Factor
0
Half Life
3.12 ± 0.08 ms
Spin0
Quadrupole Moment
0
Discovery Year1967
Parity+

244Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)97%
β+ (β+ decay; β+ = ϵ + e+)2%
α (α emission)1%

245Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
245.075354 ± 0.00021 Da
Mass Number245
G-Factor
Half Life
4.2 ± 1.3 s
Spin1/2
Quadrupole Moment
0
Discovery Year1967
Parity+

245Fm Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)7%
SF (spontaneous fission)0.3%

246Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
246.075353334 ± 0.000014675 Da
Mass Number246
G-Factor
0
Half Life
1.54 ± 0.04 s
Spin0
Quadrupole Moment
0
Discovery Year1966
Parity+

246Fm Decay Modes
Decay ModeIntensity
α (α emission)93.2%
SF (spontaneous fission)6.8%
ϵ (electron capture)1.3%

247Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
247.076944 ± 0.000194 Da
Mass Number247
G-Factor
Half Life
31 ± 1 s
Spin7/2
Quadrupole Moment
Discovery Year1967
Parity+

247Fm Decay Modes
Decay ModeIntensity
α (α emission)64%
β+ (β+ decay; β+ = ϵ + e+)%

248Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
248.077185451 ± 0.000009122 Da
Mass Number248
G-Factor
0
Half Life
34.5 ± 1.2 s
Spin0
Quadrupole Moment
0
Discovery Year1958
Parity+

248Fm Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%
SF (spontaneous fission)0.1%

249Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
249.078926042 ± 0.000006668 Da
Mass Number249
G-Factor
Half Life
1.6 ± 0.1 m
Spin7/2
Quadrupole Moment
Discovery Year1960
Parity+

249Fm Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)%
α (α emission)33%

250Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
250.079519765 ± 0.000008468 Da
Mass Number250
G-Factor
0
Half Life
31 ± 1.1 m
Spin0
Quadrupole Moment
0
Discovery Year1954
Parity+

250Fm Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)0.0069%
ϵ (electron capture)%

251Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
251.08154513 ± 0.000015342 Da
Mass Number251
G-Factor
Half Life
5.3 ± 0.08 h
Spin9/2
Quadrupole Moment
Discovery Year1957
Parity-

251Fm Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)98.2%
α (α emission)1.8%

252Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
252.082466019 ± 0.000005604 Da
Mass Number252
G-Factor
0
Half Life
25.39 ± 0.04 h
Spin0
Quadrupole Moment
0
Discovery Year1956
Parity+

252Fm Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)0.0023%
+ (double β+ decay)%

253Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
253.085180945 ± 0.000001662 Da
Mass Number253
G-Factor
Half Life
3 ± 0.12 d
Spin1/2
Quadrupole Moment
0
Discovery Year1957
Parity+

253Fm Decay Modes
Decay ModeIntensity
ϵ (electron capture)88%
α (α emission)12%

254Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
254.086852424 ± 0.000001978 Da
Mass Number254
G-Factor
0
Half Life
3.24 ± 0.002 h
Spin0
Quadrupole Moment
0
Discovery Year1954
Parity+

254Fm Decay Modes
Decay ModeIntensity
α (α emission)99.9408%
SF (spontaneous fission)0.0592%

255Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
255.089963495 ± 0.000004223 Da
Mass Number255
G-Factor
Half Life
20.07 ± 0.07 h
Spin7/2
Quadrupole Moment
Discovery Year1954
Parity+

255Fm Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)2.4%

256Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
256.091771699 ± 0.000003241 Da
Mass Number256
G-Factor
0
Half Life
157.1 ± 1.3 m
Spin0
Quadrupole Moment
0
Discovery Year1955
Parity+

256Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)91.9%
α (α emission)8.1%

257Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
257.095105419 ± 0.000004669 Da
Mass Number257
G-Factor
Half Life
100.5 ± 0.2 d
Spin9/2
Quadrupole Moment
Discovery Year1964
Parity+

257Fm Decay Modes
Decay ModeIntensity
α (α emission)99.79%
SF (spontaneous fission)0.21%

258Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
258.097077 ± 0.000215 Da
Mass Number258
G-Factor
0
Half Life
370 ± 14 us
Spin0
Quadrupole Moment
0
Discovery Year1971
Parity+

258Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)100%
α (α emission)%

259Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
259.100596 ± 0.000304 Da
Mass Number259
G-Factor
Half Life
1.5 ± 0.2 s
Spin
Quadrupole Moment
Discovery Year1980
Parity

259Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)100%

260Fm

AbundanceRadioactive ☢️
Relative Atomic Mass
260.102809 ± 0.000467 Da
Mass Number260
G-Factor
0
Half Life
Spin0
Quadrupole Moment
0
Discovery Year
Parity+

260Fm Decay Modes
Decay ModeIntensity
SF (spontaneous fission)%

History

Fermium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952. It was identified by Albert Ghiorso and co-workers at the University of California, Berkeley in collaboration with the Argonne and Los Alamos National Laboratories, in the fallout from the Ivy Mike nuclear test. The new element was produced by the nuclear fission of 17 neutrons with uranium-238. Named after Nobel laureate Enrico Fermi, one of the pioneers of nuclear physics

DiscoverersArgonne, Los Alamos, U of Calif
Discovery LocationUnited States
Discovery Year1953
Etymology (Name Origin)Named in honor of the scientist Enrico Fermi.
PronunciationFER-mi-em (English)
Fermium is harmful due to its radioactivity
Sixteen isotopes of fermium are known to exist

Uses

Fermium is used for scientific research purposes only. It has no significant commercial applications.

Sources

Produced by bombarding lighter transuranium elements with still lighter particles or by neutron capture.

Abundance
Abundance in Earth's crust
Abundance in Oceans
Abundance in Human Body
0 %
Abundance in Meteor
0 %
Abundance in Sun
0 %
Abundance in Universe
0 %

Nuclear Screening Constants