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Element Fact
The liquid helium-4 possesses the most unusual physical properties that defy common sense. Below 2.2 K it becomes a superfluid that can flow, against gravity, up the wall of a container.

Berkelium, Bk

berkelium sample

Atomic number: 97
Atomic mass: [247] (no stable nuclide)
Natural abundance: -
Isotopes: -

History and Production

Derived from the place Berkeley, home of the University of California. It was first produced by S.G. Thompson, A. Ghiorso and G.T. Seaborg in 1949, by bombarding 241Am with helium ion. The isotope subsequently produced, 243Bk, has a half-life of 4.5 hours. However, its properties can more properly be studied with 249Bk which has a longest half-life of 320 days. Berkelium probably has not yet been prepared in elemental form. However, the first visible and weighable amounts of pure berkelium chloride was produced in 1962. It weighed 3 billionth of a gram. The element so far has no commercial or technological use.

Physical Data

It is expected to be a silvery metal. The radioactive metal can easily accumulate in bones that poses serious health hazard.

Interatomic distance: -
Melting point: 1050C
Boiling point: n/a
Thermal conductivity/Wm-1K-1: 10 est. (27C)
Density/kgm-3: 14790 est.

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: -
Gibbs free energy of formation: -
Entropy: -
Heat capacity: -

Electronic data

Electronic configuration: [Rn] 5f9 7s2
Term symbol: 6H15/2
Electron affinity: -   Electronegativity (Pauline): -
Ionization energy (first, second, third): 598.007, -, - kJ/mol

Chemical properties

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