Promethium(III) bromide explained

Promethium(III) bromide is an inorganic compound, with the chemical formula of PmBr₃. It is radioactive salt. It is a crystal of the hexagonal crystal system, with the space group of P6₃/mc (No. 176).

Preparation

Promethium(III) bromide can be obtained by reacting hydrogen bromide and promethium(III) oxide:^[1]

Pm₂O₃ + 6 HBr —^500°C→ 2 PmBr₃ + 3 H₂O

Promethium(III) bromide hydrate cannot be heated to form its anhydrous form. Instead it decomposes in water to form promethium oxybromide:^[2]

PmBr₃ + H₂O(g) → PmOBr + 2 HBr

Notes and References

1. W. R. Wilmarth, G. M. Begun, R. G. Haire, et al. Raman spectra of Pm₂O₃, PmF₃, PmCl₃, PmBr₃ and PmI₃. Journal of Raman Spectroscopy, 2005. 19(4)
2. Wishnevsky . V . Theissig . W . Weigel . F . The vapor phase hydrolysis of lanthanide(III) bromides IV: Heat and free energy of the reaction PmBr₃(s) + H₂O(g) = PmOBr(s) + 2HBr(g) . Journal of the Less Common Metals . June 1984 . 99 . 2 . 321–329 . 10.1016/0022-5088(84)90230-3.