Polonium years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron. Tentatively called "radium F", polonium was discovered by Marie and Pierre Curie in 1898, and was named after Marie Curie's native land of Poland (). Poland at the time was under Russian, German, and Austro-Hungarian partition, and did not exist as an independent country. It was Curie's hope that naming the element after her native land would publicize its lack of independence. Polonium may be the first element named to highlight a political controversy. This element was the first one discovered by
Polonium dioxide cubic form is pale yellow, while the tetragonal form is red. Polonium dioxide darkens upon heating, and is chocolate brown at its sublimation point, 885 °C. The ionic radius of the ion is 1.02 or 1.04 Å; thus, the ratio of the ionic radii / is about 0.73, the lower limit of stability for the cubic crystal system, allowing polonium dioxide to have two modifications. When freshly prepared, polonium dioxide is always in the tetragonal form, and changes to the cubic form after being left to stand or after being cooled strongly. Polonium dioxide does not occur naturally due to