BERKELIUM

Introduction

Atomic Number: 97
Group: None
Atomic Weight: 247
Period: 7
CAS Number: 7440-40-6

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)

Description • Uses/Function

Berkelium, the eighth member of the actinide transition series, was discovered in December 1949 by Thompson, Ghiorso, and Seaborg, and was the fifth transuranium element synthesized. It was produced by cyclotron bombardment of milligram amounts of 241Am with helium ions at Berkeley, California. The first isotope produced had a mass number of 243 and decayed with a half-life of 4.5 hours. Eleven isotopes are now known and have been synthesized. The existence of 249Bk, with a half-life of 320 days, makes it feasible to isolate berkelium in weighable amounts so that its properties can be investigated with macroscopic quantities. One of the first visible amounts of a pure berkelium compound, berkelium chloride, was produced in 1962. It weighed 3 billionth of a gram. Berkelium probably has not yet been prepared in elemental form, but it is expected to be a silvery metal, easily soluble in dilute mineral acids, and readily oxidized by air or oxygen at elevated temperatures to form the oxide. X-ray diffraction methods have been used to identify the following compounds: BkO2, BkO3, Bkf3, BkCl, and BkOCl. 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 micrograms. Because of its rarity, berkelium presently has no commercial or technological use. Berkelium-249 is available from O.R.N.L. at a cost of $160/microgram plus packing charges. 1

Physical Properties

Form:2 alpha
Melting Point:2*  1050 °C = 1323.15 K = 1922 °F
Boiling Point:2
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Form:2 beta
Melting Point:2*  986 °C = 1259.15 K = 1806.8 °F
Boiling Point:2
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Density:3  14.78 (alpha)/13.25 (beta) g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration:  *[Rn] 7s2 5f9
Block: f
Highest Occupied Energy Level: 7
Valence Electrons: 2

Quantum Numbers:

n = 5
ℓ = 3
m = -2
ms = -½

Bonding

Ionization Potential   eV 4  kJ/mol  
Ionization Potential   eV 4  kJ/mol  
Ionization Potential   eV 4  kJ/mol  
1 6.1979    598.0

Isotopes

Nuclide Mass 5 Half-Life 5 Nuclear Spin 5 Binding Energy
235Bk 235.05658(43)# 20# s 1,774.29 MeV
236Bk 236.05733(43)# 1# min 1,782.37 MeV
237Bk 237.05700(24)# 1# min 7/2+# 1,790.44 MeV
238Bk 238.05828(31)# 2.40(8) min 1,798.51 MeV
239Bk 239.05828(25)# 3# min 7/2+# 1,806.58 MeV
240Bk 240.05976(16)# 4.8(8) min 1,814.65 MeV
241Bk 241.06023(22)# 4.6(4) min (7/2+) 1,813.41 MeV
242Bk 242.06198(22)# 7.0(13) min 2-# 1,821.48 MeV
243Bk 243.063008(5) 4.5(2) h (3/2-) 1,829.55 MeV
244Bk 244.065181(16) 4.35(15) h (4-)# 1,837.62 MeV
245Bk 245.0663616(25) 4.94(3) d 3/2- 1,845.69 MeV
246Bk 246.06867(6) 1.80(2) d 2(-) 1,853.76 MeV
247Bk 247.070307(6) 1.38(25)E+3 a (3/2-) 1,852.52 MeV
248Bk 248.07309(8)# >9 a 6+# 1,860.59 MeV
249Bk 249.0749867(28) 330(4) d 7/2+ 1,868.66 MeV
250Bk 250.078317(4) 3.212(5) h 2- 1,876.73 MeV
251Bk 251.080760(12) 55.6(11) min (3/2-)# 1,875.49 MeV
252Bk 252.08431(22)# 1.8(5) min 1,883.56 MeV
253Bk 253.08688(39)# 10# min 1,891.63 MeV
254Bk 254.09060(32)# 1# min 1,890.39 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 5

Abundance

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:5.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(8) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).