Berkelium

97

curium ← berkelium → californium


Tb
↑
Bk
↓
(Uqs)




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] 5f9 7s2


Electrons per shell
2, 8, 18, 32, 27, 8, 2


Physical properties


Phase
solid


Density (near r.t.)
(alpha) 14.78 g/cm³


Density (near r.t.)
(beta) 13.25 g/cm³


Melting point
(beta) 1259 K
(986 °C, 1807 °F)


Atomic properties


Oxidation states
3, 4


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·K)


CAS registry number
7440-40-6


Notable isotopes




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

330 d

α

5.526

245Am


SF

-

-


β-

0.125

249Cf


Berkelium (chemical symbol Bk, atomic number 97) is a synthetic, radioactive chemical element, classified as an actinide. It 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[1] to be synthesized. Currently, the main interest in this element lies in basic research, and practical applications have yet to be developed.

Contents

1 History
2 Notable characteristics

2.1 Isotopes


3 Compounds
4 Biological role
5 See also
6 Notes
7 References
8 External links
9 Credits



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 330 days), was later synthesized by subjecting a 244Cm target with an intense beam of neutrons.

Notable characteristics
Berkelium is an inner transition metal of the actinide series, located in period 7 of the periodic table, between curium and californium. Weighable amounts of 249Bk (half-life 314 days) have been produced, making 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 undergo oxidation in the air at elevated temperatures and would be soluble in dilute mineral acids.

Isotopes
Many radioisotopes of berkelium have been characterized, with the most stable being 247Bk, with a half-life of 1,380 years; 248Bk, with a half-life of more than 9 years; and 249Bk, with a half-life of 330 days. All 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 (t½ 23.7 hours). The isotopes of berkelium range in atomic weight from 235.057 amu (235Bk) to 254.091 amu (254Bk).

Compounds
X-ray diffraction techniques have been used to identify various berkelium compounds such as berkelium dioxide (BkO2), berkelium trioxide (BkO3), berkelium fluoride (BkF3), and berkelium oxychloride (BkOCl). In 1962, visible amounts of berkelium chloride (BkCl3) were isolated that weighed 3 billionths of a gram. This was the first time visible amounts of a pure berkelium compound were produced.

Biological role
Berkelium plays no biological role. It is thought that, like other actinides, it is capable of bioaccumulation in skeletal tissue.

See also
Chemical element
Inner transition metal
Metal
Periodic table
Radioactive decay
Notes

↑ "Transuranic elements" are chemical elements with atomic numbers greater than that of uranium (atomic number 92).


ReferencesISBN links support NWE through referral fees
Emsley, John. Nature's Building Blocks: An A–Z Guide to the Elements. Oxford University Press, 2001. ISBN 0198503407
Greenwood, N. N., and A. Earnshaw. Chemistry of the Elements, 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann, 1998. ISBN 0750633654. Online version. Retrieved August 27, 2019.
Hampel, Clifford A. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corp, 1968. ISBN 0442155980
Morss, Lester R., Norman M. Edelstein, and Jean Fuger, eds. The Chemistry of the Actinide and Transactinide Elements, 3rd ed., 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer, 2006. ISBN 1402035551
Stwertka, Albert. Guide to the Elements, rev. ed. Oxford University Press, 1998. ISBN 0195080831
External links
All links retrieved January 20, 2022.

Berkelium: the essentials WebElements.
It's Elemental: Berkelium – Jefferson Lab.

Credits
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