An Overview about the Chemical Element Polonium


Symbol: Po

Atomic Number: 84

Atomic Mass: 209.0 amu (atomic mass units)

Melting Point: 254.0 C (527.15 K, 489.2 F)

Boiling Point: 962.0 C (1235.15 K, 1763.6 F)

Number of Protons: 84

Number of Electrons: 84

Number of Neutrons: 125

Classification: Metalloid

Crystal Structure: Monoclinic

Density @ 293 K: 9.4 grams per cubic centimeter

Color: Silvery

The highly radioactive element polonium was discovered by the Nobel award winning scientist Marie Sklodowska Curie in 1888. It was named after her country of origin, Poland. Working with her husband Pierre Curie she discovered the element in the uranium ore pitchblende from Joachimsthal, Bohemia. The radioactivity within the pitchblende was far in excess than that of the uranium extracted from it. They reasoned that another radioactive element was responsible for this excess. Following this reasoning the Curies discovered not only polonium but also went on to discover the element radium.

Polonium is only found in trace amounts in pitchblende and the Curies had to refine several tons of the material before making their discovery. One ton of uranium ore contains only about 100 micrograms of polonium. Marie Curie died of aplastic anemia a condition that can be caused by exposure to radiation but at the time of her experiments this danger was not known.

Polonium will dissolve in weak acids but is only slightly soluble in alkaline solutions. Polonium is highly toxic and very rare so very little other chemical data is available.

Polonium has over forty isotopes all of which are radioactive. The isotope with the longest half life is polonium-209 at 102 years. The shortest half life belongs to polonium-212 at 0.299 microseconds. Polonium-209 decays by alpha decay to form lead-205.

Owing to its rarity in nature when polonium is required it is made by bombarding the element bismuth with neutrons in a nuclear reactor. Globally the production of polonium is probably less than 100 grams a year.

This element has a few uses but owing to its extreme radioactivity is must be specially shielded to prevent harm to the user.

* Polonium has been used as an antistatic agent for machinery used for paper, wire and sheet metal rolling. Other safer beta emitters are now generally used for this purpose.

* Its antistatic properties allow it to be used in the brushes used to remove dust from photographic films.

* Combined with beryllium it is used as a neutron source.

* It provides a power source for nuclear batteries.

* Polonium-210 is being investigated as a lightweight source of thermonuclear power for space craft. This isotope has a half life of 138.39 is a strong alpha emitter. One gram of polonium-210 can create 140 Watts of energy.