  berkelium is a transuranic radioactive chemical element with symbol&nbsp;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 university of california radiation laboratory where it was discovered in december 1949. this was the fifth transuranium element discovered after neptunium, plutonium, curium and americium. the major isotope of berkelium, berkelium-249, is synthesized in minute quantities in dedicated high-flux nuclear reactors, mainly at the oak ridge national laboratory in tennessee, usa, and at the research institute of atomic reactors in dimitrovgrad, russia. the production of the second-important isotope berkelium-247 involves the irradiation of the rare isotope curium-244 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 of scientific research which is mostly directed at the synthesis of heavier transuranic elements and transactinides. a 22&nbsp;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 element ununseptium 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 a culmination of the russiaâus collaboration on the synthesis of elements 113 to 118. 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&nbsp;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 helium nuclei. ==characteristics== ===physical=== thumb|double-hexagonal close packing with the layer sequence abac in the crystal structure of Î±-berkelium (a: green, b: blue, c: red)|alt=sequential layers of spheres arranged from top to bottom: grgbgrgb (g=green, r=red, b=blue) berkelium is a soft, silvery-white, radioactive actinide metal. in the periodic table, it is located to the right of the actinide curium, to the left of the actinide californium and below the lanthanide terbium with which it shares many similarities in physical and chemical properties. its density of 14.78&nbsp;g/cm3 lies between those of curi
Actinides Berkelium Chemical_elements Synthetic_elements University_of_California,_Berkeley