| Discovery date | 1898 |
| Discovered by | Marie Curie |
| Origin of the name | Polonium is named after Poland, the native country of Marie Curie, who first isolated the element. |
| Allotropes | α-Po, β-Po |
| Group | 16 | Melting point | 254 oC, 489.2 oF, 527.15 K |
| Period | 6 | Boiling point | 962 oC, 1763.6 oF, 1235.15 K |
| Block | p | Density (kg m-3) | 9400 |
| Atomic number | 84 | Relative atomic mass | 208.982 |
| State at room temperature | Solid | Key isotopes | 209Po, 210Po |
| Electron configuration | [Xe] 4f145d106s26p4 | CAS number | 7440-08-6 |
| ChemSpider ID | 4886482 | ChemSpider is a free chemical structure database | |
| Atomic radius, non-bonded (Å) | 1.970 | Covalent radius (Å) | 1.42 |
| Electron affinity (kJ mol-1) | 183.322 |
Electronegativity (Pauling scale) |
2.000 |
|
Ionisation energies (kJ mol-1) |
1st
811.827
2nd
-
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
|
||
|
|
| Common oxidation states | 6, 4, 2 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 209Po | 208.982 | - | 128 y | α | |
| 210Po | 209.983 | - | 138.4 d | α | |
|
Molar heat capacity (J mol-1 K-1) |
Unknown | Young's modulus (GPa) | Unknown | |||||||||||
| Shear modulus (GPa) | Unknown | Bulk modulus (GPa) | Unknown | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
|
|||||||||||||
| Pressure (Pa) |
|
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Uranium ores contain minute traces of polonium at levels of parts per billion. Despite this, in 1898 Marie Curie and husband Pierre Curie extracted some from pitchblende (uranium oxide, U3O8) after months of painstaking work. The existence of this element had been forecast by the Mendeleev who could see from his periodic table that there might well be the element that followed bismuth and he predicted it would have an atomic weight of 212. The Curies had extracted the isotope polonium-209 and which has a half-life of 103 years.
Before the advent of nuclear reactors, the only source of polonium was uranium ore but that did not prevent its being separated and used in anti-static devices. These relied on the alpha particles that polonium emits to neutralise electric charge.
| Listen to Polonium Podcast |
|
Transcript :
Chemistry in Its Element - Polonium(Promo)
You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.
Chris Smith
Hello, this week in Chemistry in its Element the story of a substance that was named to snub Russia, power space probes keeps paper static free and has even been used as a murder weapon in London. To reveal the secrets of Marie Curie's element, and that's Polonium, here's Johnny Ball
Johnny Ball
Polonium, (element 84), was discovered in 1898 and named after Poland, the homeland of Marie Curie (Ne Sklodowska) who found it with her husband Pierre Curie. This loyalty was a direct affront to Russia who had dominated Poland for so long. The only way she could become educated whilst a teenager, was by risking imprisonment by the Russians by attending secret underground schools, which had to change locations every couple of days. It was only by escaping to Paris, following her older brother and sister, that she was able to forge a career. She was so poor in the early years in Paris, that she sometimes fainted through lack of food. Still she worked tirelessly.
In 1894 she met Pierre, who had made a name for himself in discovering piezoelectricity and was one of her lecturers. They married in July 1895. She wore a black dress as it would be serviceable for her work in the laboratory. They did not exchange rings, but bought each other a bicycle, on which they honeymooned.
X rays had been discovered by Roentgen (Nov 95) and Uranium radiation by Becquerel (Feb 96) in Paris. Working with him (98), Marie coined the phrase "radio activity" and decided to make this here object of study, because no one else was doing it. They realised that radiation was coming from the very atoms and that this was a sign of the atoms breaking up. Only by studying the break up of atoms through radiation, were scientists able to clearly understand how atoms are made up. For this the Curies and Becquerel shared the Nobel Prize for Physics in 1903.
Pierredied in a tragic accident in 1906, which may have been the result of the pain he was in through radiation burns and sickness. (More on this if you wish) For discovering Polonium and Radium, Marie received the Nobel Prize for Chemistry in 1911, becoming the only woman to receive two such prizes.
Natural Polonium Po - 210, is still very rare and forms no more than 100 ?g per ton of Uranium ores. As well as Po - 210, Isotopes Po -211 - 212 - 214 - 215 - 216 and - 218 all occur in the chains of radio active elements, as they decay to form Lead Pb -208. However, they exist for very little time indeed, Po 212 comes in two forms, one having a half life of 45.1 seconds and the other of 300 nanoseconds (300/1,000,000,000ths of a second).
Because it is so rare, Polonium is made by first making Bismuth (also found in pitchblende). Bismuth -209 is found and then artificially changed to Bismuth -210 which then decays to form Polonium -210.
Polonium has a position in the periodic table that could make it a metal, a metalloid or a nonmetal. It is classed as a metal as it's electrical conductivity decreases as it's temperature rises. Because of this property it is used in industry to eliminate dangerous static electricity in making paper or sheet metal.
Because of its short half life, it's decay generates considerable heat (141 W per gram of metal). It can be used as a convenient and very light heat source to generate reliable thermoelectric power in space satellites and lunar stations, as no moving parts are involved.
Chris Smith
Johnny Ball lifting the lid on the radioactive element polonium discovered by Marie Curie and her husband Pierre. Next time on Chemistry in its Element we remain radioactive much like the substance itself with earth scientist Ian Farnan.
Ian Farnan
Anyone familiar with the iconic image of the mushroom cloud understands the tremendous explosive power of a correctly controlled detonation of plutonium. The energy density is mind-boggling: a sphere of metal 10 cm in diameter and weighing just 8 Kg is enough to produce an explosion at least as big as the one that devastated Nagasaki in 1945.
Chris Smith
Ian Farnan with what promises to be an explosive edition of Chemistry in its Element next week. I'm Chris Smith, thank you for listening and see you next time.
(Promo)
Chemistry in its elementis brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements.
(End promo) |
Mining and Sourcing data: British Geological Survey – natural environment research council.
Text: John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.