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84
Po
(209)
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Marie Curie in 1883, 16 years old. Polonium was the first element she discovered, 15 years later.
| Classification: | Polonium is a chalcogen and a metalloid |
| Color: | silvery-gray |
| Atomic weight: | (209), no stable isotopes |
| State: | solid |
| Melting point: | 254 oC, 527 K |
| Boiling point: | 960 oC, 1233 K |
| Shells: | 2,8,18,32,18,6 |
| Electron configuration: | [Xe] 4f14 5d10 6s2 6p4 |
| Density @ 20oC: | 9.4 g/cm3 |
| Atomic volume: | 22.23 cm3/mol |
| Structure: | simple cubic |
| Hardness: |
Discovery of Polonium
Polonium was the first element Marie and Pierre Curie discovered.
They discovered polonium and then radium in 1898, while working in Paris, investigating radioactivity in pitchblende (uranium oxide).
At the time of the discovery they wrote: "We thus believe that the substance that we have extracted from pitchblende contains a metal never known before, akin to bismuth in its analytic properties. If the existence of this new metal is confirmed, we suggest that it should be called polonium after the name of the country of origin of one of us."
In accordance with the Curies' wishes, polonium is named after Poland, the country of Marie Curie's birth.
The dangers of working with radioactive elements were not known when the Curies' made their discoveries. Their laboratory notebooks from this time are so radioactive that they are now stored in a lead-lined case. (1)
Appearance & Characteristics
Part of the uranium decay series. Three isotopes of polonium are produced in nature, either by the decay of radon gas itself or by the decay of atoms resulting from radon's decay. Image by Tosaka.
Harmful effects:
Polonium is harmful both through its chemical toxicity and its radioactivity. Polonium-210 is an alpha emitter. As such it is very hazardous if swallowed or inhaled. Exposure to polonium increases the risk of getting various cancers.
Characteristics:
Polonium is a rare, silvery-gray, radioactive low-melting metalloid. Polonium readily reacts with dilute acids, but only slightly with alkalis. All of its isotopes are radioactive. 210Po emits a blue glow, as the air around it is excited by the decay products. 1 gram of Po emits as many alpha particles as 5 kilograms of radium. The energy released by polonium's alpha decay is considerable and heats the volume around it. The energy released is so large (140 W/g) that a capsule containing about half a gram reaches a temperature above 500 oC.
Polonium is used to eliminate static electricity produced during processes such as rolling paper, wire and sheet metal. However, beta decay sources are more commonly used as they are less dangerous. 210Po can be used as an atomic heat source but because of the isotope's short half-life (138.4 days), it doesn't provide power for long-term uses. Polonium is also used in anti-static brushes to eliminate dust on photographic film. It is sealed in brushes to control the radioactive emissions.
Polonium is harmful both through its chemical toxicity and its radioactivity. Polonium-210 is an alpha emitter. As such it is very hazardous if swallowed or inhaled. Exposure to polonium increases the risk of getting various cancers.
Characteristics:
Polonium is a rare, silvery-gray, radioactive low-melting metalloid. Polonium readily reacts with dilute acids, but only slightly with alkalis. All of its isotopes are radioactive. 210Po emits a blue glow, as the air around it is excited by the decay products. 1 gram of Po emits as many alpha particles as 5 kilograms of radium. The energy released by polonium's alpha decay is considerable and heats the volume around it. The energy released is so large (140 W/g) that a capsule containing about half a gram reaches a temperature above 500 oC.
Uses of Polonium
Polonium is used to eliminate static electricity produced during processes such as rolling paper, wire and sheet metal. However, beta decay sources are more commonly used as they are less dangerous. 210Po can be used as an atomic heat source but because of the isotope's short half-life (138.4 days), it doesn't provide power for long-term uses. Polonium is also used in anti-static brushes to eliminate dust on photographic film. It is sealed in brushes to control the radioactive emissions.
Abundance & Isotopes
Abundance earth's crust: Of the order of 1 part per quadrillion.
Abundance solar system: negligible
Cost, pure: per 100g
Cost, bulk: per 100g
Source: Polonium is a very rare element due to the short half-life of all its isotopes. It is found in uranium ores in minute quantities. It can be obtained by bombarding natural bismuth, 209Bi , with neutrons to give 210Bi, which then decays to 210Po via β decay. Approximately 100 g of polonium is synthesized each year.
Isotopes: Polonium has 29 isotopes whose half-lives are known, with mass numbers 190 to 218. None are stable. The most stable isotope is 209Po, with a half-life of 102 years.
Abundance solar system: negligible
Cost, pure: per 100g
Cost, bulk: per 100g
Source: Polonium is a very rare element due to the short half-life of all its isotopes. It is found in uranium ores in minute quantities. It can be obtained by bombarding natural bismuth, 209Bi , with neutrons to give 210Bi, which then decays to 210Po via β decay. Approximately 100 g of polonium is synthesized each year.
Isotopes: Polonium has 29 isotopes whose half-lives are known, with mass numbers 190 to 218. None are stable. The most stable isotope is 209Po, with a half-life of 102 years.
Energies
Specific heat capacity: 0.12 J g-1 K-1 0.12 J g-1 K-1
Heat of fusion: 13 kJ mol-1
1st ionization energy: 812 kJ mol-1
3rd ionization energy: kJ mol-1
Heat of fusion: 13 kJ mol-1
1st ionization energy: 812 kJ mol-1
3rd ionization energy: kJ mol-1
Heat of atomization: 142 kJ mol-1
Heat of vaporization: 120 kJ mol-1
2nd ionization energy: kJ mol-1
Electron affinity: 180 kJ mol-1
Heat of vaporization: 120 kJ mol-1
2nd ionization energy: kJ mol-1
Electron affinity: 180 kJ mol-1
Oxidation & Electrons
Shells: 2,8,18,32,18,6
Minimum oxidation number: -2
Min. common oxidation no.: -2
Electronegativity (Pauling Scale): 2.0
Minimum oxidation number: -2
Min. common oxidation no.: -2
Electronegativity (Pauling Scale): 2.0
Electron configuration: [Xe] 4f14 5d10 6s2 6p4
Maximum oxidation number: 6
Max. common oxidation no.: 4
Polarizability volume: 6.8 Å3
Maximum oxidation number: 6
Max. common oxidation no.: 4
Polarizability volume: 6.8 Å3
Reactions & Compounds
Reaction with air: mild, ⇒ PoO2
Reaction with 15 M HNO3:
Oxide(s): PoO2, PoO2
Hydride(s): PoH2
Reaction with 15 M HNO3:
Oxide(s): PoO2, PoO2
Hydride(s): PoH2
Reaction with 6 M HCl: mild, ⇒ PoCl2
Reaction with 6 M NaOH: none
Chloride(s): PoCl2
Reaction with 6 M NaOH: none
Chloride(s): PoCl2
Radius
Atomic radius: 190 pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): pm
Ionic radius (1- ion): pm
Ionic radius (3+ ion): pm
Ionic radius (1- ion): pm
Conductivity
Thermal conductivity: 0.2 W m-1 K-1
Electrical conductivity: 0.7 x 106 S m-1
References
1. "Marie and Pierre Curie and the Discovery of Polonium and Radium". Nobelprize.org. 16 Feb 2012 http://www.nobelprize.org/nobel_prizes/physics/articles/curie/
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