Isotopes of Polonium
|Isotope||Atomic Mass||Half-life||Mode of Decay||Nuclear Spin||Nuclear Magnetic Moment|
|Po-206||205.98047||8.80 days||EC to Bi-206;
α to Pb-202
|0||No data available|
|Po-207||206.98158||5.80 hours||EC to Bi-207;
α to Pb-203
|Po-208||207.98123||2.898 years||EC to Bi-208;
α to Pb-204
|0||No data available|
|Po-209||208.982404||125.3 +/- 3.2 years||EC to Bi-209;
α to Pb-205
|Po-210||209.98286||138.38 days||α to Pb-206||0||No data available|
Polonium was discovered in 1898 by Marie Sklodowska Curie. It is named for Poland, her birthplace.
Two crystalline forms of polonium exist: the alpha allotrope, with a simple cubic low-temperature form and a density of 9.196 g/cm3; and the beta modification, with a rhombohedral high-temperature form and a density of 9.398 g/cm3. Both allotropic forms coexist from 18-54 ºC and vaporize at 962 ºC. Polonium is practically insoluble in water and soluble in dilute mineral acids. At ordinary temperatures, it oxidizes slowly in air, forming its basic oxide. The metal dissolves in dilute hydrochloric acid, forming pink-red polonium. It dissolves in concentrated nitric acid and aqua regia, oxidizing to the Po4+ state.
Because of its radioactivity and alpha emission, polonium forms many types of radiolytic oxidation-reduction products. It is used on brushes to remove dusts from photographic film, as well as in instruments to eliminate static charges. It is also used as a small source to generate alpha particles and neutrons, and as a power source in devices where its radioactive decay energy is converted to electrical energy.
As with other radioactive substances, exposure to polonium's ionizing radiation can cause cancer. When ingested, it tends to accumulate in the liver, kidneys and spleen, causing radiation damage from the alpha particles. All operations and handling must be carried out by mechanical means, in leak-proof boxes, behind thick neutron shields.
Properties of Polonium
|Standard state||Solid at 298 °K|
|CAS Registry ID||7440-08-6|
|Group in periodic table||16|
|Period in periodic table||6|
|Block in periodic table||p-block|
|Melting point||254 °C|
|Boiling point||962 °C|
|Thermal conductivity||20 (estimated) W/(m·K)|
|Electrical resistivity||40 x 10-8 Ω·m|
|Heat of vaporization||About 100 kJ·mol-1|
|Heat of fusion||About 13 kJ·mol-1|
|Density of solid||9.20 g/cm3 (alpha form)|
|Atomic radius||1.64 Å|
|Atomic volume||23.53 cm3/g-atom|
|Oxidation states||-2, 0, +2, +4, +6|