Polonium the Curies while they were investigating the cause of pitchblende radioactivity. Pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated radium. German scientist Willy Marckwald successfully isolated 3 milligrams of polonium in 1902, though at the time he believed it was a new element, which he dubbed "radio-tellurium", and it was not until 1905 that it was demonstrated to be the same as polonium.
Polonium a gamma ray with a maximum energy of 803 keV. Polonium is a radioactive element that exists in two metallic allotropes. The alpha form is the only known example of a simple cubic crystal structure in a single atom basis at STP, with an edge length of 335.2 picometers; the beta form is rhombohedral. The structure of polonium has been characterized by X-ray diffraction and electron diffraction. Po (in common with Pu) has the ability to become airborne with ease: if a sample is heated in air to , 50% of it is vaporized in 45 hours to form diatomic