   #copyright

Berkelium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


              97              curium ← berkelium → californium
              Tb
             ↑
             Bk
             ↓
             (Uqs)

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                    Name, Symbol, Number berkelium, Bk, 97
                                                 Chemical series actinides
                                            Group, Period, Block n/a, 7, f
                                      Appearance unknown, probably silvery
                                                    white or metallic gray
                                                   Atomic mass (247) g/mol
                                     Electron configuration [Rn] 5f^9 7s^2
                                Electrons per shell 2, 8, 18, 32, 27, 8, 2
                                                       Physical properties
                                                               Phase solid
                              Density (near r.t.) (alpha) 14.78 g·cm^−3
                               Density (near r.t.) (beta) 13.25 g·cm^−3
                                              Melting point (beta) 1259  K
                                                     (986 ° C, 1807 ° F)
                                                         Atomic properties
                                     Electronegativity 1.3 (Pauling scale)
                                       Ionization energies 1st: 601 kJ/mol
                                                             Miscellaneous
                                  Crystal structure hexagonal close-packed
                                                 Magnetic ordering no data
                         Thermal conductivity (300 K) 10 W·m^−1·K^−1
                                             CAS registry number 7440-40-6
                                                         Selected isotopes

   CAPTION: Main article: Isotopes of berkelium

                                  iso   NA  half-life DM  DE ( MeV)   DP
                                 ^245Bk syn 4.94 d    ε   0.810     ^245Cm
                                                      α   6.455     ^241Am
                                 ^246Bk syn 1.8 d     α   6.070     ^242Am
                                                      ε   1.350     ^246Cm
                                 ^247Bk syn 1380 y    α   5.889     ^243Am
                                 ^248Bk syn >9 y      α   5.803     ^244Am
                                 ^249Bk syn 320 d     α   5.526     ^245Am
                                                      SF  -         -
                                                      β^- 0.125     ^249Cf

                                                                References

   Berkelium ( IPA: /bəˈkiːliəm/) is a synthetic element in the periodic
   table that has the symbol Bk and atomic number 97. A radioactive
   metallic element in the actinide series, berkelium was first
   synthesized by bombarding americium with alpha particles (helium ions)
   and was named after Berkeley, California and the University of
   California, Berkeley. Berkelium was the fifth transuranic element to be
   synthesized.

Notable characteristics

   Weighable amounts of ^249Bk (half-life 314 days) make it possible to
   determine some of its properties using macroscopic quantities. As of
   2004 it had not been isolated in its elemental form, but it is
   predicted to be a silvery metal that would easily oxidize in air at
   elevated temperatures and would be soluble in dilute mineral acids.

   X-ray diffraction techniques have been used to identify various
   berkelium compounds such as berkelium dioxide (BkO[2]), berkelium
   fluoride (BkF[3]), berkelium oxychloride (BkOCl), and berkelium
   trioxide (BkO[3]). In 1962 visible amounts of berkelium chloride were
   isolated that weighed 3 billionths of a gram. This was the first time
   visible amounts of a pure berkelium compound were produced.

   Like other actinides, berkelium bio-accumulates in skeletal tissue.
   This element has no known uses outside of basic research and plays no
   biological role.

History

   Berkelium was first synthesized by Glenn T. Seaborg, Albert Ghiorso,
   Stanley G. Thompson, and Kenneth Street, Jr at the University of
   California, Berkeley in December 1949. The team used a cyclotron to
   bombard a milligram-sized target of ^241Am with alpha particles to
   produce ^243Bk ( half-life 4.5 hours) and two free neutrons. One of the
   longest lived isotopes of the element, ^249Bk (half-life 320 days), was
   later synthesized by subjecting a ^244Cm target with an intense beam of
   neutrons.

Isotopes

   19 radioisotopes of berkelium have been characterized, with the most
   stable being ^247Bk with a half-life of 1380 years, ^248Bk with a
   half-life of >9 years, and ^249Bk with a half-life of 320 days. All of
   the remaining radioactive isotopes have half-lifes that are less than 5
   days, and the majority of these have half lifes that are less than 5
   hours. This element also has 2 meta states, with the most stable being
   ^248mBk (t[½] 23.7 hours). The isotopes of berkelium range in atomic
   weight from 235.057 amu (^235Bk) to 254.091 amu (^254Bk).
   Retrieved from " http://en.wikipedia.org/wiki/Berkelium"
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   with only minor checks and changes (see www.wikipedia.org for details
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