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Introduction
What is polonium? Its history? Physical and chemical properties? Characteristics? Solid state form? Detection(alpha detection)? Occurrence and production? Harmful effects ? Toxicity ? Well-known poisoning cases?? Uses and Applications of polonium? Products containing polonium ??
What is polonium??
Polonium is a chemical element with the symbol Po and atomic number 84, discovered by Maria Curie.
A rare and highly radioactive element with no stable isotopes, polonium is chemically similar to bismuth and tellurium.
It emites alpha particel. polonium is sometimes classified as a metalloid.
However, other sources say that on the basis of its properties and behavior, it is "unambiguously a metal.
It has a very dangerous environmental effects, It is very toxic element.
History This element was the first one
discovered by the Curies while they were investigating the cause of pitchblende radioactivity. The pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than both the uranium and thorium put together. This spurred the Curies on to find additional radioactive elements. The Curies first separated out polonium from the pitchblende in July 1898, and five months later, also isolated radium.
Chemical and physical properties of polonium
Atomic number 84 Atomic mass (210) g.mol -1
Density 9.51 g.cm-3 at 20°C Melting point 254 °C Boiling point 962 °C Electronic shell [ Xe ] 4f14 5d10 6s2 6p4
Phase solid Density (near r.t.) 9.196 g·cm−3
Crystal structure cubic
Phase solid Magnetic ordering
nonmagnetic Electrical resistivity (0 °C) (α)
0.40 µΩ·m Thermal conductivity
20 W·m−1·K−1
CharacteristicsIsotopes: Polonium has 33 known isotopes, all of which
are radioactive. They have atomic masses that range from 188
to 220 u. 209Po (half-life 103 years) and 208Po (half-life
2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron.
210Po is an alpha emitter that has a half-life of 138.4 days; it decays directly to its stable daughter isotope, 206Pb.(the most widely available).
A milligram of 210Po emits about as many alpha particles per second as 5 grams of 226Ra. A few curies (1 curie equals 37 gigabecquerels, (1 Ci = 37 GBq) of 210Po emit a blue glow which is caused by excitation of surrounding air.
About one in 100,000 alpha emissions causes an excitation in the nucleus which then results in the emission of a gamma ray with a maximum energy of 803 keV.However, it is the alpha particles, not the side effect of an occasional gamma ray, that results in 210Po decay. The gamma radiation level from polonium is below the normal background.
Most stable isotopes
Isotope Natural abundan
ce
Half life Decay mode
Decay enargy(M
ev(
Decay product
208Po Synthetic radioisoto
pe
2.898 year α
β+
5.2151.401
204Pb208Bi
209Po Synthetic radioisoto
pe
103 year αβ+
4.9791.893 205Pb
209Bi
210Po Trace radioisoto
pe
138.376 day
α 5.307206Pb
Solid state form:
Polonium is a radioactive element that exists in two metallic allotropes.
The alpha form is the only known example of a simple cubic crystal structure in a single atom basis, with an edge length of 335.2 picometers.
The beta form is rhombohedral. The structure of polonium has been characterized by X-
ray diffraction and electron diffraction. 210Po (in common with 238Pu) has the ability to
become airborne with ease: if a sample is heated in air to 55 °C (131 °F), 50% of it is vaporized in 45 hours.More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are spalled off by the alpha decay.
Chemistry
The chemistry of polonium is similar to that of tellurium and bismuth.
Polonium dissolves readily in dilute acids, but is only slightly soluble in alkalis.
Polonium solutions are first colored in pink by the Po2+ ions, but then rapidly become yellow because alpha radiation from polonium ionizes the solvent and converts Po2+ into Po4+. This process is accompanied by bubbling and emission of heat and light by glassware due to the absorbed alpha particles; as a result, polonium solutions are volatile and will evaporate within days unless sealed.
Detection
Alpha counting: The best way to test for (and measure)
many alpha emitters is to use alpha-particle spectroscopy.
An alternative method is to use internal liquid scintillation where the sample is mixed with a scintillation cocktail.
A third energy dispersive method for counting alpha particles is to use a semiconductor detector.
Occurrence and production
Polonium is a very rare element in nature because of the short half-life of all its isotopes.
It is found in uranium ores at about 0.1 mg per metric ton (1 part in 1010),which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful.
Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers
Harmful effects
Polonium is harmful both through its chemical toxicity and its radioactivity.
Exposure to polonium increases the risk of getting various cancers.
When it breaks down, it gives off alpha particles these particles are tiny, atom-sized particles that can destroy cells.
Toxicity of Polonium
Weight for polonium's toxicity is around 100 times greater than hydrogen cyanide. It is chemically toxic Even in microgram amounts, handling 210Po is extremely dangerous, requiring specialized equipment and strict handling procedures.
The main hazard is its intense radioactivity (as an alpha emitter), which makes it very difficult to handle safely.
Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed (though they do not penetrate the epidermis ).
Well-known poisoning cases Polonium-210 is used to poison the Russian
dissident Alexader Litvinenko in London. Palestinian leader Yasser Arafat : Abnormally
high concentrations of 210Po have been detected in clothes and personal belongings of the Palestinian leader Yasser Arafat, who died in 2004 of uncertain causes.
Clinical symptoms described in Arafat's medical reports were not consistent with polonium-210 and that conclusions could not be drawn as to whether the Palestinian leader was poisoned or not??? and that "the only way to confirm the findings would be to exhume Arafat's body to test it for polonium-210.
The dose allegedly ingested by Arafat was much smaller than the amount that killed Litvinenko, making it even harder to detect.
Products containing polonium
Tobacco:its plants fertilized by rock phosphates contain polonium-210, which emits alpha radiation estimated to cause about 11,700 lung cancer deaths annually worldwide.
Food: Polonium is also found in the food chain, especially in seafood.
Uses and Applications of polonium Mixed and alloyed with beryllium to provide a
source of neutrons, and it is a source of alpha particles.
Used for eliminating static charges from textile mills.
Polonium was also part of brushes(removing dust from photographic films) or more complex tools that eliminate static charges in photographic plates.
Is a source of radiation and a heat source in space vehicles.
Alpha particles emitted by polonium ionize air molecules that neutralize charges on the nearby surfaces.
Po is used as an atomic heat source to power radioisotope thermoelectric generators via thermoelectric materials(Thermoelectric power in space satellites).
Measuring the thickness of industrial coatings via attenuation of alpha radiation.
neutron trigger or initiator for nuclear weapons and for inspections of oil wells.
Antistatic devices.
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