QUICK REFERENCE
- Symbol: Po
- Atomic Number: 84
- Atomic Weight: [209]
- Element Classification: Metalloid
- Discovered By: Marie Curie and Pierre Curie
- Discovery Date: 1898
- Name Origin: Named after Poland, the native country of Marie Curie
- Density(g/cc): 9.196 (calculated)
- Melting Point: 254°C
- Boiling Point: 962°C
- Appearance: Silvery-gray metal
- Atomic Radius(pm): 135 (estimated)
Discovery
Polonium was discovered in 1898 by Marie Curie and her husband Pierre Curie. The discovery was made while the Curies were investigating the cause of radioactivity in pitchblende, a uranium-rich mineral. They isolated polonium from pitchblende, recognizing it as a new element because of its intense radioactivity. Marie Curie named it “polonium” in honor of her native country, Poland, which was under foreign domination at the time, as a gesture of patriotism.
Relation to Other Elements
Polonium is a metalloid in the chalcogen group, which also includes oxygen, sulfur, selenium, and tellurium. It shares some properties with its group neighbors but is unique due to its radioactivity. Polonium has 33 known isotopes, all of which are radioactive. The most stable isotope, polonium-209, has a half-life of 125.2 years. Polonium exhibits metallic, nonmetallic, and semiconductor properties, depending on the allotrope and physical conditions.
Natural Occurrence
Polonium is extremely rare in nature and is usually found in uranium ores at concentrations of up to 0.1 mg per ton. It is produced in minute amounts from the decay of uranium-238 and is more commonly produced in nuclear reactors by bombarding bismuth-209 with neutrons.
Uses
Due to its intense radioactivity and scarcity, polonium’s applications are limited and highly specialized:
- Industrial Radiography: Polonium can be used as a portable source of neutrons and alpha particles for industrial radiography to inspect welded joints and metal parts.
- Thermoelectric Power: Polonium has been used in space missions as a heat source to generate thermoelectric power in satellites and lunar stations, taking advantage of the heat released by its radioactive decay.
- Anti-static Devices: Polonium has been used in devices to eliminate static charges in machinery and processes where dust attraction is problematic, such as in the manufacturing of photographic films and synthetic fibers.
The discovery of polonium marked a significant milestone in the study of radioactivity and contributed to the awarding of two Nobel Prizes to Marie Curie: one in Physics (shared with Pierre Curie and Henri Becquerel) and another in Chemistry. Due to its high radioactivity, handling polonium requires strict safety measures, and its use is restricted to areas where its unique properties are indispensable.