   #copyright

Fermium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


              100            einsteinium ← fermium → mendelevium
              Er
             ↑
             Fm
             ↓
             (Upn)

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                     Name, Symbol, Number fermium, Fm, 100
                                                 Chemical series actinides
                                            Group, Period, Block n/a, 7, f
                                      Appearance unknown, probably silvery
                                                    white or metallic gray
                                                   Atomic mass (257) g/mol
                                    Electron configuration [Rn] 5f^12 7s^2
                                Electrons per shell 2, 8, 18, 32, 30, 8, 2
                                                       Physical properties
                                                               Phase solid
                                                     Melting point 1800  K
                                                    (1527 ° C, 2781 ° F)
                                                         Atomic properties
                                     Electronegativity 1.3 (Pauling scale)
                                       Ionization energies 1st: 627 kJ/mol
                                                             Miscellaneous
                                             CAS registry number 7440-72-4
                                                         Selected isotopes

   CAPTION: Main article: Isotopes of fermium

                                   iso   NA  half-life DM DE ( MeV)   DP
                                  ^252Fm syn 25.39 h   SF -         -
                                                       α  7.153     ^248Cf
                                  ^253Fm syn 3 d       ε  0.333     ^253Es
                                                       α  7.197     ^249Cf
                                  ^255Fm syn 20.07 h   SF -         -
                                                       α  7.241     ^251Cf
                                  ^257Fm syn 100.5 d   α  6.864     ^253Cf
                                                       SF -         -

                                                                References

   Fermium ( IPA: /ˈfɛː(r)miəm/) is a synthetic element in the periodic
   table that has the symbol Fm and atomic number 100. A highly
   radioactive metallic transuranic element of the actinide series,
   fermium is made by bombarding plutonium with neutrons and is named
   after nuclear physicist Enrico Fermi.

Notable characteristics

   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. There are no known uses of fermium outside of basic
   research. Fermium is the eighth transuranic element.

History

   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 whose team members included Ghiorso,
   Stanley G. Thompson, Gary H. Higgins, Glenn T. Seaborg (from the
   Radiation Laboratory and Department of Chemistry of the University of
   California), Martin H. Studier, P.R. Fields, Sherman M. Fried, H.
   Diamond, J.F. Mech, G.L. Pyle, John R. Huizenga, A. Hirsch, W.M.
   Manning (from the Argonne National Laboratory), C.I. Browne, H. Louise
   Smith, and R.W. Spence (from the Los Alamos Scientific Laboratory).
   Samples of sea coral impacted from the first thermonuclear explosion of
   November 1952 were used.

   All these findings were kept secret until 1955 due to Cold War
   tensions, however. 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 but the isotope they produced was later positively
   identified as ^250Fm.

Isotopes

   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-lifes that are less than 5.4 hours, and the majority
   of these have half lifes that are less than 3 minutes. This element
   also has 1 meta state, ^250mFm (t[½] 1.8 seconds). The isotopes of
   fermium range in atomic weight from 242.073 amu (^242Fm) to 259.101 amu
   (^259Fm).
   Retrieved from " http://en.wikipedia.org/wiki/Fermium"
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   with only minor checks and changes (see www.wikipedia.org for details
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