Periodic Table -> Protactinium


Protactinium Details

Protactinium Symbol: Pa

Protactinium Atomic Number: 91

Protactinium Atomic Weight: 231.05

What is Protactinium?

Protactinium (atomic number 91) is a metal discovered by Oswald Gohring and Kasimir Fajans in 1913. It was only in 1934 when the element was first isolated. Protactinium-231 was discovered by John Cranston and Frederick Soddy and Lisa Meitner and Otto Hahn in 1918. This metal is found in uranium ores while its isotopes are present in uranium-238 and uranium-235. Protactinium is a rare metal that reacts with inorganic acids, water vapor, and oxygen. It is toxic, radioactive, and harmful for human health. Because protactinium is a rare element, it is not used for commercial purposes and only for scientific research. There are no stable isotopes, and protactinium-231 is the most stable one. The element has 5 naturally occurring isotopes and 29 isotopes in total.

Protactinium is shiny, malleable, and silver-gray in color. The ionic radius, boiling point, and Van Der Waals radius are unknown. It is solid at room temperature and has orthorhombic crystal structure. As a member of the actinide group, it is found in animals and plant species, groundwater, rocks, and soils. Protactinium can be obtained as a byproduct of plutonium, thorium, and uranium and is produced through nuclear fission. Barium, lithium, and calcium fluoride are also used to obtain protactinium at high temperatures of about 1400 °C.

It is a conductor with paramagnetic properties and was previously called brevium because of the element’s short life. The oxidation states in solutions and solids are +5 and +4, and the metal forms different compounds with red, yellow, brown, black, and white color. The metal forms insoluble and soluble solids in solutions and has an oxidation state of +3 in compounds such as nitrides and hydrides. The element also forms compounds such as pentoxide, dioxide, fluoride, chloride, and others.

Sources and Applications
Protactinium is found in ores in Zaire and the Democratic Republic of Congo. It has been extracted from waste at the UK’s Atomic Energy Authority. Spent nuclear fuel is also used to extract the metal.
In households, it is found in smoke detectors in the form of protactinium-233 which is the product of decay of neptunium-237. The isotope itself has a half life of only 27 days (in comparison, the half life of protactinium-231 is over 32,000 years). While the metal has no commercial or industrial applications, some of its isotopes are used in different fields. Combined with thorium-230, protactinium-231 is used by scientists for radiometric dating, which is a method for dating carbon and rocks. Other possibilities have been explored such as the use of isotopes to study climatic conditions in different historic periods as well as the building of nuclear weapons. Due to the fact that this is a rare element, it is also expensive – 1 gram of pure protactinium costs about $280.

Environmental and Health Effects
Exposure occurs through breathing, drinking water, and ingestion. When ingested, a very small amount of the metal remains in the body and enters the bloodstream. The element is deposited in the kidneys, liver, and bones and is considered a health hazard. Because of its radioactivity, exposure can cause cancer, and protective equipment is required when handling. A glove box is usually used for different manipulations. While ingestion is more common, gamma exposure and inhalation are major risk factors. One of its isotopes, protactinium-213 is very toxic and according to scientists, its toxicity is 2.5×108 higher compared to hydrogen cyanide. Actinium-227 is also considered a health hazard. Because of the fact that protactinium is present is small amounts, it is not a major soil or water contaminant.

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