Protactinium(IV) oxide is a chemical compound with the formula Pa O₂. The black oxide is formed by reducing Pa₂O₅ with

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

at 1 550 °C. Protactinium(IV) oxide does not dissolve in H₂SO₄, HNO₃, or HCl solutions, but reacts with HF.Boris F. Myasoedov, H. W. Kirby, & Ivan G. Tananaev (2006) Protactinium, Chapter 4 in Morss, Lester R. & Edelstein, Norman M. & Fuger, Jean, (edit.
The Chemistry of the Actinide and Transactinide Elements
(PDF) (3. painos). Dordrecht: Springer. ss. 161–252. As protactinium(IV) oxide, like other protactinium compounds, is

radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

, toxic and very rare, it has no known technological use.

References

Oxides Protactinium compounds Fluorite crystal structure {{Inorganic-compound-stub