Electron Shell Configuration: [Xe] 4f14 5d10 6s2 6p4
Minimum oxidation number: -2
Maximum oxidation number: 6
Minimum common oxidation number: -2
Maximum common oxidation no: 4special: simple cubic
Appearance & Characteristics
Structure:: special: simple cubic
Color: blue glow
Hardness: mohs
Toxicity: ?
Characteristics: Radioactive; 2 forms
Uses: thermoelectric power
Reactions
Reaction with air: mild, =>PoO2
Reaction with 6M HCl: mild, =>PoCl2
Reaction with 15M HNO3: ?
Reaction with 6M NaOH: ?
Other Forms
Number of isotopes: ?
Oxide(s): PoO PoO2
Hydride(s): ?
Chloride(s): PoCl2 PoCl2
Radius
Atomic Radius: 168 pm
Ionic radius (1- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): pm
Ionic radius (3+ ion): pm
Conductivity
Thermal conductivity: J/m-sec-deg
Electrical conductivity: 1/mohm-cm
Polarizability: 6.8 A^3
Abundance
Source: pitchblende, synthetic
Relative abundance solar system: log
Abundance earth's crust: -9.7 log
Estimated crustal abundance: 2×10-10 milligrams per kilogram
Estimated oceanic abundance: 1.5×10-14 milligrams per liter
History
(Poland, native country of Mme. Curie) Polonium, also called Radium F, was the first element discovered by Mme. Curie in 1898 while seeking the cause of radioactivity of pitchblend from Joachimsthal, Bohemia. The electroscope showed it separating with bismuth.
Sources
Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium.
In 1934, scientists discovered that when they bombarded natural bismuth (209Bi) with neutrons, 210Bi, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors.
Properties
Polonium-210 is a low-melting, fairly volatile metal, 50% of which is vaporized in air in 45 hours at 55?C. It is an alpha emitter with a half-life of 138.39 days. A milligram emits as many alpha particles as 5 g of radium.
The energy released by its decay is so large (140W/g) that a capsule containing about half a gram reaches a temperature above 500C. The capsule also presents a contact gamma-ray dose rate of 0.012 Gy/h. A few curies (1 curie = 3.7 x 1010Bq) of polonium exhibit a blue glow, caused by excitation of the surrounding gas.
Polonium is readily dissolved in dilute acids, but is only slightly soluble in alkali. Polonium salts of organic acids char rapidly; halide amines are reduced to the metal.
Uses
Because almost all alpha radiation is stopped within the solid source and its container, giving up its energy, polonium has attracted attention for uses as a lightweight heat source for thermoelectric power in space satellites.
Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. The element has been used in devices for eliminating static charges in textile mills, etc.; however, beta sources are both more commonly used and less dangerous. It is also used on brushes for removing dust from photographic films. The polonium for these is carefully sealed and controlled, minimizing hazards to the user.
Isotopes
Twenty five isotopes of polonium are known, with atomic masses ranging from 194 to 218. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life 103 years) and mass 208 (half-life 2.9 years) can be prepared by alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron, but these are expensive to produce.
Metallic polonium has been prepared from polonium hydroxide and some other polonium compounds in the presence of concentrated aqueous or anhydrous liquid ammonia. Two allotropic modifications are known to exist.
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