| 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 |
Po
Polonium
84
[209]
| Group | 16 | Melting point | 254°C, 489°F, 527 K |
| Period | 6 | Boiling point | 962°C, 1764°F, 1235 K |
| Block | p | Density (g cm−3) | 9.20 |
| Atomic number | 84 | Relative atomic mass | [209] |
| State at 20°C | Solid | Key isotopes | 209Po, 210Po |
| Electron configuration | [Xe] 4f145d106s26p4 | CAS number | 7440-08-6 |
| ChemSpider ID | 4886482 | ChemSpider is a free chemical structure database | |
Image explanation
An image based on Luna E-1, the first spacecraft of the Soviet ‘Luna’ programme. Later Luna spacecraft carried ‘Lunokhod’ rovers to the moon. These were the first rovers to explore the moon’s surface and were powered by polonium.
Appearance
A silvery-grey, radioactive semi-metal.
Uses
Polonium is an alpha-emitter, and is used as an alpha-particle source in the form of a thin film on a stainless steel disc. These are used in antistatic devices and for research purposes.
A single gram of polonium will reach a temperature of 500°C as a result of the alpha radiation emitted. This makes it useful as a source of heat for space equipment.
It can be mixed or alloyed with beryllium to provide a source of neutrons.
Biological role
Polonium has no known biological role. It is highly toxic due to its radioactivity.
Natural abundance
Polonium is a very rare natural element. It is found in uranium ores but it is uneconomical to extract it. It is obtained by bombarding bismuth-209 with neutrons to give bismuth-210, which then decays to form polonium. All the commercially produced polonium in the world is made in Russia.
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.
| Atomic radius, non-bonded (Å) | 1.97 | Covalent radius (Å) | 1.42 |
| Electron affinity (kJ mol−1) | 183.3 |
Electronegativity (Pauling scale) |
2.0 |
|
Ionisation energies (kJ mol−1) |
1st
811.828
2nd
-
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
|
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| 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 | |
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Specific heat capacity (J kg−1 K−1) |
Unknown | Young's modulus (GPa) | Unknown | |||||||||||
| Shear modulus (GPa) | Unknown | Bulk modulus (GPa) | Unknown | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
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| Pressure (Pa) |
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| Listen to Polonium Podcast |
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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. (End promo) 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 "radioactivity" 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. Pierre died in a tragic accident in 1906. In driving rain he seemed to walk in front of a large horse-drawn wagon, and a wheel shattered his head. Some think the pain he was in as a result of radiation burns and sickness may have caused his lack of awareness. Marie was devastated, but her work continued. For discovering polonium and radium, she received the Nobel Prize for Chemistry in 1911, becoming the only woman ever to receive two such prizes. However, there was still more success due for the family. Her daughter Irene also became a scientist, and in 1934, Marie saw Irene and her husband Frederick Joliot-Curie produce the first ever artificial radioactive element. This led to our modern ability to manipulate almost every element for our specific scientific needs. Irene and Frederick also received the Nobel Prize in 1935, but sadly Marie had now died. Natural polonium, Po-210, is still very rare and forms no more than 100 billions of a gram per ton of uranium ore. 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. This process requires a nuclear reactor, so it is not an easy element to source. It was a shocking discovery that the former Russian agent Alexander Litvinenko was poisoned with this very radioactive element. The alpha particles it emits are so weakly penetrating it could easily have been carried in a simple sealed container, and would have to be ingested, for example in a cup of tea, to do any serious harm. However, once inside the body, as it continued to disintegrate, it would become fatal. 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 its electrical conductivity decreases as its 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, its 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 element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements. (End promo)
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Visual Elements images and videos
© Murray Robertson 1998-2017.
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Derived in part from material provided by the British Geological Survey © NERC.
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Produced by The Naked Scientists.
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
© Murray Robertson 1998-2017.
Data
W. M. Haynes, ed., CRC Handbook of Chemistry and Physics, CRC Press/Taylor and Francis, Boca Raton, FL, 95th Edition, Internet Version 2015, accessed December 2014.
Tables of Physical & Chemical Constants, Kaye & Laby Online, 16th edition, 1995. Version 1.0 (2005), accessed December 2014.
J. S. Coursey, D. J. Schwab, J. J. Tsai, and R. A. Dragoset, Atomic Weights and Isotopic Compositions (version 4.1), 2015, National Institute of Standards and Technology, Gaithersburg, MD, accessed November 2016.
T. L. Cottrell, The Strengths of Chemical Bonds, Butterworth, London, 1954.
Uses and properties
John Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
Thomas Jefferson National Accelerator Facility - Office of Science Education, It’s Elemental - The Periodic Table of Elements, accessed December 2014.
Periodic Table of Videos, accessed December 2014.
Supply risk data
Derived in part from material provided by the British Geological Survey © NERC.
History text
Elements 1-112, 114, 116 and 117 © John Emsley 2012. Elements 113, 115, 117 and 118 © Royal Society of Chemistry 2017.
Podcasts
Produced by The Naked Scientists.
Periodic Table of Videos
Created by video journalist Brady Haran working with chemists at The University of Nottingham.
