Chemical element, symbol Bk and atomic number 97 / From Wikipedia, the free encyclopedia

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Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

Quick facts: Berkelium, Pronunciation, Appearance, Mass nu...
Berkelium, 97Bk
Mass number[247]
Berkelium in the periodic table


Atomic number (Z)97
Groupf-block groups (no number)
Periodperiod 7
Block  f-block
Electron configuration[Rn] 5f9 7s2
Electrons per shell2, 8, 18, 32, 27, 8, 2
Physical properties
Phase at STPsolid
Melting pointbeta: 1259 K (986 °C, 1807 °F)
Boiling pointbeta: 2900 K (2627 °C, 4760 °F)
Density (near r.t.)alpha: 14.78 g/cm3
beta: 13.25 g/cm3
Heat of fusion7.92 kJ/mol (calculated)
Atomic properties
Oxidation states+2, +3, +4, +5[1]
ElectronegativityPauling scale: 1.3
Ionization energies
  • 1st: 601 kJ/mol
Atomic radiusempirical: 170 pm
Color lines in a spectral range
Spectral lines of berkelium
Other properties
Natural occurrencesynthetic
Crystal structure double hexagonal close-packed (dhcp)
Double hexagonal close packed crystal structure for berkelium
Thermal conductivity10 W/(m⋅K)
Magnetic orderingparamagnetic
CAS Number7440-40-6
Namingafter Berkeley, California, where it was discovered
DiscoveryLawrence Berkeley National Laboratory (1949)
Isotopes of berkelium
Main isotopes[2] Decay
abun­dance half-life (t1/2) mode pro­duct
245Bk synth 4.94 d ε 245Cm
α 241Am
246Bk synth 1.8 d α 242Am
ε 246Cm
247Bk synth 1380 y α 243Am
248Bk synth >300 y[3] α 244Am
249Bk synth 330 d β 249Cf
α 245Am
Symbol_category_class.svg Category: Berkelium
| references

The major isotope of berkelium, 249Bk, is synthesized in minute quantities in dedicated high-flux nuclear reactors, mainly at the Oak Ridge National Laboratory in Tennessee, United States, and at the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. The longest-lived and second-most important isotope, 247Bk, can be synthesized via irradiation of 244Cm with high-energy alpha particles.

Just over one gram of berkelium has been produced in the United States since 1967. There is no practical application of berkelium outside scientific research which is mostly directed at the synthesis of heavier transuranium elements and superheavy elements. A 22-milligram batch of berkelium-249 was prepared during a 250-day irradiation period and then purified for a further 90 days at Oak Ridge in 2009. This sample was used to synthesize the new element tennessine for the first time in 2009 at the Joint Institute for Nuclear Research, Russia, after it was bombarded with calcium-48 ions for 150 days. This was the culmination of the Russia–US collaboration on the synthesis of the heaviest elements on the periodic table.

Berkelium is a soft, silvery-white, radioactive metal. The berkelium-249 isotope emits low-energy electrons and thus is relatively safe to handle. It decays with a half-life of 330 days to californium-249, which is a strong emitter of ionizing alpha particles. This gradual transformation is an important consideration when studying the properties of elemental berkelium and its chemical compounds, since the formation of californium brings not only chemical contamination, but also free-radical effects and self-heating from the emitted alpha particles.

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