Protactinium is a chemical element; it has symbol Pa and atomic number 91. It is a dense, radioactive, silvery-gray actinide metal which readily reacts with oxygen, water vapor, and …

protactinium (Pa), radioactive chemical element of the actinoid series of the periodic table, rarer than radium; its atomic number is 91. It occurs in all uranium ores to the extent of 0.34 part per …

Small amounts of protactinium are found naturally in uranium ores. It is also found in spent fuel rods from nuclear reactors, from which it is extracted. Mendeleev said there should be an …

Protactinium is one of the rarest and most expensive naturally occurring elements. The average concentrations of protactinium in the Earth's crust is typically on the order of a few parts per …

Jun 28, 2025 · Protactinium (Pa) is a rare, radioactive metal with atomic number 91 and a silvery-gray appearance. It belongs to the actinide series and occurs naturally in trace amounts in …

Chemical element, Protactinium, information from authoritative sources. Look up properties, history, uses, and more.

Nov 14, 2025 · Protactinium is a rare and highly radioactive element in the series of actinides within the periodic table. It possesses several distinctive chemical and physical properties, …

Protactinium is the 91st element in the periodic table and has a symbol of Pa and atomic number of 91. It has an atomic weight of (231.03588) and a mass number of 231. Protactinium has …

Explore the intriguing world of Protactinium, Element 91. Learn about its history, properties, uses, and why it’s a fascinating subject in scientific research. From its discovery to its chemical …

Protactinium is a very rare shiny, silvery, highly radioactive metal that tarnishes slowly in air to the oxide. Almost all naturally occurring protactinium is the 231 isotope.