Berkelium

Berkelium, ₉₇Bk

Berkelium
Pronunciation	/bərˈkiːliəm/ (bər-KEE-lee-əm) /ˈbɜːrkliəm/ (BUR-klee-əm)
Appearance	silvery
Mass number	[247]
Berkelium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Tb ↑ Bk ↓ — curium ← berkelium → californium
Atomic number (Z)	97
Group	f-block groups (no number)
Period	period 7
Block	f-block
Electron configuration	[Rn] 5f9 7s2
Electrons per shell	2, 8, 18, 32, 27, 8, 2
Physical properties
Phase at STP	solid
Melting point	beta: 1259 K ​(986 °C, ​1807 °F)
Boiling point	beta: 2900 K ​(2627 °C, ​4760 °F)
Density (near r.t.)	alpha: 14.78 g/cm3 beta: 13.25 g/cm3
Heat of fusion	7.92 kJ/mol (calculated)
Atomic properties
Oxidation states	common: +3 +2,? +4,[1] +5[2]
Electronegativity	Pauling scale: 1.3
Ionization energies	1st: 601 kJ/mol
Atomic radius	empirical: 170 pm
Spectral lines of berkelium
Other properties
Natural occurrence	synthetic
Crystal structure	​double hexagonal close-packed (dhcp)
Thermal conductivity	10 W/(m⋅K)
Magnetic ordering	paramagnetic
CAS Number	7440-40-6
History
Naming	after Berkeley, California, where it was discovered
Discovery	Lawrence Berkeley National Laboratory (1949)
Isotopes of berkelium v e
Main isotopes[3] Decay abun­dance half-life (t1/2) mode pro­duct 245Bk synth 4.94 d ε 245Cm α 241Am 246Bk synth 1.8 d α 242Am β+ 246Cm 247Bk synth 1380 y α 243Am 248Bk synth >9 y[4] α 244Am 249Bk synth 330 d β− 249Cf α 245Am SF –
Category: Berkelium view talk edit | references

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.

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.