Polonium is a very rare radioactive element. Chemically, it is represented with the symbol Po. In the periodic table, it is placed in group 16 which is also known as chalcogen family. Other members of this family include Oxygen, Sulfur, Selenium, and Tellurium. It is the heaviest chemical element of this group. As it is highly radioactive, most of its uses are confined to research based studies.
The credit for discovering Polonium goes to Marie Curie and her husband. They discovered it in the year 1898. It is named after Poland, Marie Curie's country of origin. The couple were inspired by Henry Becquerel's discovery of radioactivity, and were doing research on Uranium ores to identify the cause of radioactivity. They found that on separating Uranium and Thorium from the ores, there was another radioactive material which was more unstable than the two elements, and exhibited higher radioactivity. After Polonium, this couple went on to discover another radioactive element Radium.
Polonium is rarely found in nature. This is because it is formed by the radioactive disintegration or breaking down of the natural form of Uranium 238 which is also a radioactive element. Moreover, it has a very short half life period. Thus the only natural source of the element is Uranium ores. Even in this ore, its concentration is very low. One metric ton of Uranium ores contains hardly 100 micrograms of Polonium.
Polonium can now be produced artificially. Its process of manufacturing was discovered in the year 1934, when scientists bombarded naturally occurring Bismuth with neutrons. Now, it is mostly prepared with the help of neutron refluxes present in nuclear reactors.
Its atomic number is 84. In all, there are 33 known isotopes of the element, which is the highest number for any element. The atomic masses of all these isotopes are in between 188 and 220, and all of them are radioactive in nature. Among them, Polonium 210 is the most commonly found isotope, and is widely used for practical applications.
Polonium is categorized as a metalloid. The term metalloid is used for those chemical elements that exhibit properties of both metals as well as non metals. It is a soft metal, and can be identified with its silvery gray color. It has extremely high volatility. In fact, if you heat the metal at 55 degrees Celsius, half the sample would be vaporized in the first 45 hours itself. The chemical properties of Polonium have lots of similarities with that of Bismuth. The element is highly soluble in acidic substances, and partially soluble in alkaline substances.
Rarely found in nature, even the artificial production of the element is barely 100 grams a year. For all these reasons, there are restricted uses of this element. Some of the key Polonium 210 uses are given below:
- Polonium 210 is widely used as source of neutrons. It is combined with beryllium for this purpose. The alpha particle emitted by the radioactive element helps in release of neutrons from Beryllium. However, one needs to own a license to use it as a neutron source.
- A small amount of the element releases a large amount of energy every second in the form of alpha particles. For this reason, it has been used in thermoelectric cells of artificial satellites.
- The brushes that are used for cleaning up accumulated dust particles from camera lenses, and photographic films have polonium 210 in them.
- It is also present in devices used for the elimination of static electricity in various machines. Such devices are needed in paper rolling machine, spinning synthetic fibers, plastic sheet manufacturing, etc.
- The isotope is used in radioisotope thermoelectric generator. This device converts the energy released by the radioactive decay of an element into electricity. It is needed as a power source for unmanned remote facilities such as lighthouse and space probe.
- Research is underway to find out whether the element can also be used as a source of heat in spacecrafts. However, it may not be used in long-term space missions because of its short half-life period.