97
  Bk  
247.000000
Berkelium

Name: Berkelium
Symbol: Bk
Atomic Number: 97
Atomic Weight: 247.000000
Family: Rare Earth Elements
CAS RN: 7440-40-6
Description: A radioactive rare earth metal.
State (25 C): Solid
Oxidation states: +3,+4

Molar Volume: unknown
Valence Electrons: 5f86d17s2

Boiling Point: unknown
Melting Point: 1259K, 986C, 1807F

Elec. Energy Level: 2, 8, 18, 32, 26, 9, 2
Isotopes: 20 + None Stable + 1 Meta State
Heat of Vaporization: unknown
Heat of Fusion: unknown
Density: 14.78 g/cm3 @ 300oK (Est.)
Specific Gravity: 14 (est.)
Atomic Radius: unknown
Ionic Radius: 0.949       
Electronegativity: 1.3 (Pauling), 1.2 (Allrod Rochow)
89
Ac
227.0
90
Th
232.0
91
Pa
231.0
92
U
238.0
93
Np
237.0
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)

1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10f8 6s2p6d1 7s2

  History

(Berkeley, home of the University of California) Berkelium, the eighth member of the actinide transition series was the fifth transuranium element synthesized.  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 330 days), was later synthesized by subjecting a 244Cm target with an intense beam of neutrons.

Characteristics

Weighable amounts of 249Bk (half-life 314 days) make it possible to determine some of its properties using macroscopic quantities.  The first visible amounts of a berkelium compound, berkelium chloride (BkCl3) was produced in 1962 and weighed about 3 billionths of a gram (0.000000003 grams).  Berkelium oxychloride (BkOCl), berkelium fluoride (BkF3), berkelium dioxide (BkO2) and berkelium trioxide (BkO3) have been identified and studied with a method known as X-ray diffraction.  As with other actinide elements, berkelium tends to accumulate in the skeletal system.  The maximum permissible body burden of 249Bk in the human skeleton is about 0.0004 ug.  Because of its rarity, berkelium presently has no known uses outside of basic research and plays no biological role.  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. Berkelium-249 is available from O.R.N.L. at a cost of $160/ug plus packing charges.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10 5f9
6s2 6p6
7s2

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.

Compounds

Berkelium Oxychloride, BkOCl
Berkelium Fluoride, BkF3 Berkelium Dioxide, BkO2
Berkelium Trioxide, BkO3 Berkelium Chloride, BkCl3

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 330 days.  All of the remaining radioactive isotopes have half-lives that are less than 5 days, and the majority of these have half-lives that are less than 5 hours.  This element also has 2 meta states, with the most stable being 248mBk (t 23.7 hours).  The isotopes of berkelium range in atomic weight from 235.057 amu (235Bk) to 254.091 amu (254Bk).

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
235Bk 235.05658 ~20 s
236Bk 236.05733 ~1 min
237Bk 237.05700 ~1 min
238Bk 238.05828 2.40 min
239Bk 239.05828 ~3 min
240Bk 240.05976 4.8 min
241Bk 241.06023 4.6 min
242Bk 242.06198 7.0 min
243Bk 243.063008 4.5 h
244Bk 244.065181 4.35 h
245Bk 245.0663616 4.94 d
246Bk 246.06867 1.80 d
247Bk 247.070307 1.38 x 103 y
248Bk 248.07309 >9 y
248mBk   23.7 h
249Bk 249.0749867 330 d
250Bk 250.078317 3.212 h
251Bk 251.080760 55.6 min
252Bk 252.08431 1.8 min
253Bk 253.08688 ~10 min
254Bk 254.09060 ~1 min

Precautions

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

atom.gif (700 bytes)

Berkelium Data

 

Atomic Structure

Atomic Radius (): unknown
Atomic Volume: unknown
Covalent Radius: unknown
Crystal Structure: Hexagonal
Ionic Radius: 0.949

Chemical Properties

Electrochemical Equivalents: 3.0727 g/amp-hr
Electron Work Function: unknown
Electronegativity: 1.3 (Pauling); 1.2 (Allrod Rochow)
Heat of Fusion: unknown
First Ionization Potential: 6.23
Second Ionization Potential: unknown
Third Ionization Potential: unknown
Valence Electron Potential (-eV): 45.5
Ionization Energy (eV): 6.23 eV

Physical Properties

Atomic Mass Average: 247
Boiling Point: unknown
Melting Point: 1259K, 986C, 1807F
Heat of Vaporization: unknown
Coefficient of Lineal Thermal Expansion/K-1: N/A
Electrical Conductivity: unknown
Thermal Conductivity: 0.1 W/cmK
Density: 14.78 g/cc @ 300K
Enthalpy of Atomization: unknown
Enthalpy of Fusion: unknown
Enthalpy of Vaporization: unknown
Molar Volume: unknown
Specific Heat: unknown
Vapor Pressure: unknown
Estimated Crustal Abundance: unknown
Estimated Oceanic Abundance: unknown