Protactinium

Protactinium, chemical element, symbol Pa; for physical constants see Periodic Table. Discovered in 1917 by 2 teams of scientists working independently; Otto Hahn and Lise Meitner of Germany and Frederick Soddy and John Cranston of Great Britain. It is found in the mineral pitchblende in minute quantities. Protactinium is a lustrous, radioactive metal, and a member of the actinide series. The element was initially prepared by decomposing its iodide in a vacuum with an electrically heated filament. The longest lived is an alpha emitter with a half-life of 32,500 years. It is a dangerous and toxic material.