Berkelium compounds

Berkelium forms a number of chemical compounds, where it normally exists in an oxidation state of +3 or +4, and behaves similarly to its lanthanide analogue, terbium.

[1] Like all actinides, berkelium easily dissolves in various aqueous inorganic acids, liberating gaseous hydrogen and converting into the trivalent oxidation state.

The existence of divalent berkelium salts is uncertain and has only been reported in mixed lanthanum chloride-strontium chloride melts.

[9] Upon heating to 1200 °C, the cubic Bk2O3 transforms to a monoclinic structure, which further converts to a hexagonal phase at 1750 °C; the latter transition is reversible.

[11] A divalent oxide BkO has been reported as a brittle gray solid with a face centered cubic (fcc) structure and a lattice constant a = 496.4 pm, but its exact chemical composition is uncertain.

The most stable phase at low temperatures has an orthorhombic symmetry, isotypic with yttrium(III) fluoride (Pearson symbol oP16, space group Pnma, No.

Upon heating to 350 to 600 °C, it transforms to a trigonal structure found in lanthanum(III) fluoride (Pearson symbol hP24, space group P3c1, No.

[16][18][20] Visible amounts of berkelium(III) chloride (BkCl3) were first isolated and characterized in 1962, and weighed only 3 billionths of a gram.

It can be prepared by introducing hydrogen chloride vapors into an evacuated quartz tube containing berkelium oxide at a temperature of about 500 °C.

Besides a chemical contamination, 249Cf, as an alpha emitter brings undesirable self-damage of the crystal lattice due to the resulting self-heating.

Berkelium(III) phosphate (BkPO4) has been prepared as a solid, which shows strong fluorescence under argon laser (514.5 nm line) excitation.

Whereas the trihydride has a hexagonal symmetry, the dihydride crystallizes in an fcc structure with the lattice constant a = 523 pm.

[13] Thermal decomposition at about 600 °C in an argon atmosphere (to avoid oxidation to BkO2) of Bk2(SO4)3·12H2O yields the body-centered orthorhombic crystals of berkelium(IV) oxysulfate (Bk2O2SO4).