protactinium
Protactinium is a rare, radioactive element with the symbol Pa and atomic number 91. It is part of the actinide series and is found in trace amounts in uranium ores. Protactinium is silvery-gray in color and has a high melting point, making it a dense metal.
This element was first isolated in 1913 by Hermann Strassmann and Otto Hahn. Protactinium has no significant commercial applications but is of interest in scientific research, particularly in nuclear chemistry and physics. Its isotopes are used in studies related to nuclear reactions and the behavior of heavy elements.