Polonium

Polonium (symbol: Po) is a chemical element with atomic number 84. It is one of the radioactive elements, meaning that the nuclei of its atoms are unstable and decay by emitting radiation. All isotopes of polonium are radioactive; there is no stable isotope.

Polonium was discovered in 1898 and was found by Marie Curie and Pierre Curie while studying uranium ore obtained from pitchblende. The name comes from Poland (Polonia in Latin), the country of Marie Curie's origin. Polonium is located on the periodic table in group 16, the same group as sulfur and selenium, though its properties are closer to those of metals.

Physical and Chemical Properties

Polonium is a hard, silvery-metallic substance that conducts electricity and heat. Because of the high rate of its decay, some of the polonium collected produces considerable heat, a fraction of which can cause it to emit a faint blue glow when stimulated in air. Chemically, it can form compounds such as polonium oxides and halides, and exhibits oxidation states of varying degrees.

Isotopes

The most well-known isotope is Po-210, which is part of the natural decay chain of uranium-238. Po-210 emits alpha radiation (helium nuclei) with a half-life of approximately 138 days. Consequently, its storage does not persist long, and it must be continuously produced. Other isotopes, such as Po-208 and Po-209, have longer half-lives but are extremely rare in nature and are produced in nuclear reactors.

Production and Use

Polonium-210 is mostly produced in nuclear reactors by irradiating bismuth-209 with neutrons, after which it is separated chemically. The most common application is in static elimination devices used in factories, and when combined with beryllium to produce a neutron source. The heat generated has also been used in power sources and heating systems for high-altitude aircraft.

Toxicity and Safety

The alpha radiation from Po-210 does not penetrate skin, but if the substance is ingested through food, inhalation, or a wound, it is extremely toxic, as the radiation damages all cells within the body. For this reason, polonium is handled under strict containment procedures. In 2006, the death of Alexander Litvinenko in London was linked to poisoning by Po-210, an event that increased public concern about the element.