polonides

Polonides are chemical compounds that involve polonium in a charged form, typically as the polonide ion Po2−, or as compounds in which polonium behaves as an anionic component bonded to electropositive metals. They are most commonly encountered as binary compounds of polonium with alkali or alkaline-earth metals, with reported examples such as calcium polonide (CaPo), strontium polonide (SrPo), and barium polonide (BaPo). The term also extends to more complex systems that include lanthanide or actinide elements forming polonide-containing phases.

In crystal chemistry, polonides often adopt simple ionic lattices, such as rock-salt type structures, where Po2− is balanced by divalent or monovalent cations. The Po2− anion is large and highly polarizable, which gives rise to primarily ionic bonding with some covalent character depending on composition and structure. Physical properties of polonides typically reflect their ionic nature and the heavy, radioactive polonium center, making them insulators or wide-band-gap solids in many cases.

Preparation of polonides generally involves high-temperature reactions between elemental polonium and the metallic component under inert or reducing conditions, or the reduction of polonide precursors. Because polonium is highly radioactive, handling polonides requires specialized radiological safety protocols and facilities. Polonides are thermally sensitive and can decompose or undergo radiolytic changes upon heating or prolonged irradiation.

Due to the radioactivity and scarcity of polonium, polonides are mainly of academic interest, contributing to the broader understanding of polonium chemistry, heavy-metal polyanion behavior, and the chemistry of metal polonides in solid-state systems.