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Atomic symbol: Po |
Atomic number: 84 |
Atomic weight: (209) |
Atomic volume: 22.23 cm3/mol |
Density: 9.4 g/cm3 |
Period Number: 6 |
Group number: 16 |
Group name: Metal, Chalcogen |
Element classification: Metal |
Phase at room temperature: Solid |
Melting Point: 527.2 K |
Boiling point: 1235 K |
Heat of fusion: ? |
Heat of vaporization: ? |
Ionization Energy: 8.417 eV |
1st ionization energy: 812 kJ/mole |
2nd ionization energy: kJ/mole |
3rd ionization energy: kJ/mole |
Electronegativity: 2 |
Electron affinity: 180 kJ/mole |
Specific heat: 0.12 J/gK |
Heat atomization: 144 kJ/mole atoms |
Shells: 2,8,18,32,18,6 |
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 |
Reaction with air: mild, =>PoO2 |
Reaction with 6M HCl: mild, =>PoCl2 |
Reaction with 15M HNO3: ? |
Reaction with 6M NaOH: ? |
Number of isotopes: ? |
Oxide(s): PoO PoO2 |
Hydride(s): ? |
Chloride(s): PoCl2 PoCl2 |
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 |
Thermal conductivity: J/m-sec-deg |
Electrical conductivity: 1/mohm-cm |
Polarizability: 6.8 A^3 |
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 |
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(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. |
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. |
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.
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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.
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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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SEKOM Handelsges.m.b.H.... |
Our company is a private firm founded in 1990 with aim to develop export and import with Russia. We do promote EU industrial and consumer goods in Russia and strongly support marketing of Russian and CIS industrial products and services.
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