Berkelium melting point

Some properties of berkelium metal have been reported. Thus, its melting point is 986 + 25 °C and its volatility, relative to its congeners, is in the order Cm < Bk < Am < Cf. Its chemical behaviour is described as somewhat similar to Sm, and it does not correspond, as a metal, to Tb or Lu. It reacts with hydrogen at 225 °C to give BkH2, which is isomorphous with other lanthanide and actinide hydrides of the type MH2+ (x < 1). BkO may be formed as an impurity in the production of metallic Bk. 

Berkelium exists in such small amounts that very litde is known about its properties. Scientists have found that it exists in two forms, known as the alpha form and the beta form. The melting points of these two forms of berkelium are 1920°F (1050°C) and 1810°F (986°C), respectively. The two forms have densities of 14.78 and 13.25 grams per cubic centimeter, about 14 times the density of water. 

A phenomenological model based on crystal structure, metallic radius, melting point, and enthalpy of sublimation has been used to arrive at the electronic configuration of berkelium metal [140]. An energy difference of 0.92 eV was calculated between the 5f 7s ground state and the 5f 6d 7s first excited state. The enthalpy of sublimation of trivalent Bk metal was calculated to be 2.99 eV (288 kJmol ), reflecting the fact that berkelium metal is more volatile than curium metal. It was also concluded that the metallic valence of the face-centered cubic form of berkelium metal is less than that of the double hexagonal close-packed modification [140]. 

There has been only one reported value for the melting point of californium metal, which was estimated to be 900 30°C from the puddling of metal particles in a thin film of the metal [70]. This melting point is lower than those reported for americium, curium or berkelium metals, but it is in accord with the higher volatility of californium metal, and the increasing trend toward divalency across the actinide series. 

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