From Wikipedia, the free encyclopedia
silvery, white or metallic gray
|Name, symbol, number
||fermium, Fm, 100
|Group, period, block
||n/a, 7, f
|Electrons per shell
||2, 8, 18, 32, 30, 8, 2 (Image)
||1800 K, 1527 °C, 2781 °F
||1.3 (Pauling scale)
||1st: 627 kJ·mol−1
Most stable isotopes
|Main article: Isotopes of
Not to be confused with "Ferrum", the Latin
name for Iron
Fermium (pronounced /ˈfɜrmiəm/, FER-mee-əm)
is a synthetic element with the symbol
Fm and atomic number 100. A highly radioactive metallic transuranic element of
the actinide series, fermium is made by
with neutrons and is named
after nuclear physicist Enrico Fermi. Fermium is the eighth transuranic element.
Electron shell diagram of fermium
Only small amounts of fermium have ever been produced or
isolated. Thus relatively little is known about its chemical
properties. Only the (III) oxidation state of the element appears
to exist in aqueous solution. 254Fm and heavier isotopes can be synthesized by
intense neutron bombardment
of lighter elements (especially uranium and plutonium). During this, successive neutron
captures mixed with beta decays build the fermium isotope. The
intense neutron bombardment conditions needed to create fermium
exist in thermonuclear
explosions and can be replicated in the laboratory (such as in
the High Flux Isotope Reactor at
Oak Ridge National
Laboratory). The synthesis of element 102 (nobelium) was confirmed when 250Fm
was chemically identified. Like all synthetic elements it is
extremely radioactive and highly toxic. fermium is a metal and not
found in nature
There are no known uses of fermium outside of basic
Fermium (after Enrico Fermi) was first discovered by a team led by Albert Ghiorso in
1952. The team found 255Fm in the debris of the first hydrogen bomb explosion (see Operation Ivy).
That isotope was created when 238U combined with 17
neutrons in the intense temperature and pressure of the explosion
(eight beta decays also occurred to create the element). The work
was overseen by the University of California Radiation
Laboratory, Argonne National
Laboratory, and Los
Alamos Scientific Laboratory. All these findings were kept
secret until 1955 due to Cold
Samples of sea coral impacted from the first thermonuclear
explosion of November 1952 were used.
In late 1953 and early 1954 a team from the Nobel Institute of
Physics in Stockholm
bombarded a 238U
target with 16O
ions, producing an alpha-emitter with an atomic weight of
~250 and with 100 protons (in
other words, element 250100).
The Nobel team did not claim discovery until 1954. The isotope they
produced was later positively identified as 250Fm.
17 radioisotopes of fermium have been
characterized, with the most stable being 257Fm with a
half-life of 100.5 days,
253Fm with a half-life of 3 days, 252Fm with
a half-life of 25.39 hours, and 255Fm with a half-life
of 20.07 hours. All of the remaining radioactive isotopes
have half-lives that are less than 5.4 hours, and the majority of
these have half-lives that are less than 3 minutes. This element
also has 1 meta state, 250mFm
(t½ 1.8 seconds). The isotopes of fermium range in atomic weight from
(242Fm) to 259.101 u (259Fm).
- ^ Ghiorso, A.; Thompson, S. G.; Higgins, G.
H. ; Seaborg, G. T.; Studier, M. H.; Fields, P. R.; Fried, S.
M.; Diamond, H.; Mech, J. F.; Pyle, G. L.; Huizenga, J. R.; Hirsch,
A.; Manning, W. M.; Browne, C. I.; Smith, H. L.; Spence, R. W.
(1955). "New Elements Einsteinium and
Fermium, Atomic Numbers 99 and 100". Physical Review
99: 1048–1049. doi:10.1103/PhysRev.99.1048. http://prola.aps.org/abstract/PR/v99/i3/p1048_1.
- ^ Albert Ghiorso (2003). "Einsteinium and Fermium".
Chemical and Engineering News. http://pubs.acs.org/cen/80th/einsteiniumfermium.html.
- ^ Atterling, Hugo; Forsling, Wilhelm; Holm,
Lennart W.; Melander, Lars; Åström, Björn (1954). "Element 100
Produced by Means of Cyclotron-Accelerated Oxygen Ions".
Physical Review 95: 585–586. doi:10.1103/PhysRev.95.585.2.