Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a radioactive metal and belongs to the actinide series of elements in the periodic table. Protactinium is a silvery-gray metal that tarnishes in air.

Key Characteristics of Protactinium:

1. Radioactivity: Protactinium is highly radioactive, and all of its isotopes are unstable. Its most stable isotope, protactinium-231, has a half-life of about 32,760 years. Protactinium emits alpha particles and beta particles during its radioactive decay.
2. Occurrence: Protactinium is a rare element in the Earth’s crust and is found in trace amounts. It is not found in its pure form in nature but is usually present as a decay product of uranium and thorium minerals.
3. Chemical Properties: Protactinium is a reactive element and readily reacts with air, water, and acids. It forms compounds with various elements, but its chemistry is not extensively studied due to its radioactivity and scarcity.
4. Applications: Due to its radioactivity and scarcity, protactinium does not have many practical applications. However, it has been used in scientific research and in some nuclear reactors for neutron sources.
5. Biological Role: Protactinium is highly radioactive and poses a significant health hazard. It has no known biological role and is toxic to living organisms.

Protactinium’s radioactivity and rarity limit its practical applications. However, it is of interest to researchers in nuclear science and has contributed to our understanding of radioactive decay and the behavior of actinide elements.