| Discovery date | 1885 |
| Discovered by | Carl Auer von Welsbach |
| Origin of the name | The name is derived from the Greek 'prasios didymos' meaning green twin. |
| Allotropes |
|
Pr
Praseodymium
59
140.908
| Group | Lanthanides | Melting point | 931°C, 1708°F, 1204 K |
| Period | 6 | Boiling point | 3520°C, 6368°F, 3793 K |
| Block | f | Density (g cm−3) | 6.77 |
| Atomic number | 59 | Relative atomic mass | 140.908 |
| State at 20°C | Solid | Key isotopes | 141Pr |
| Electron configuration | [Xe] 4f36s2 | CAS number | 7440-10-0 |
| ChemSpider ID | 22384 | ChemSpider is a free chemical structure database | |
Image explanation
The symbol is one commonly used for the astrological birth sign of Gemini (‘the twins’). The green colour, together with this symbol, reflects the origin of the element’s name, from the Greek ‘prasinos’, meaning ‘green’, and ‘didymos’, meaning ‘twin’.
Appearance
A soft, silvery metal.
Uses
Praseodymium is used in a variety of alloys. The high-strength alloy it forms with magnesium is used in aircraft engines. Mischmetal is an alloy containing about 5% praseodymium and is used to make flints for cigarette lighters. Praseodymium is also used in alloys for permanent magnets.
Along with other lanthanide elements, it is used in carbon arc electrodes for studio lighting and projection.
Praseodymium salts are used to colour glasses, enamel and glazes an intense and unusually clean yellow. Praseodymium oxide is a component of didymium glass (along with neodymium). This glass is used in goggles used by welders and glassmakers, because it filters out the yellow light and infrared (heat) radiation.
Biological role
Praseodymium has no known biological role. It has low toxicity.
Natural abundance
Praseodymium occurs along with other lanthanide elements in a variety of minerals. The two principal sources are monazite and bastnaesite. It is extracted from these minerals by ion exchange and solvent extraction.
Praseodymium metal is prepared by reducing anhydrous chloride with calcium.
Didymium was announced in 1841 by Carl Mosander. He separated if from cerium, along with lanthanum. Didymium was accepted as an element for more than 40 years but it was really a mixture of lanthanoid elements. Some chemists wondered whether didymium too might consist of more than one element, and their suspicions were confirmed when Bohuslav Brauner of Prague in 1882 showed that its atomic spectrum was not that of a pure metal. The Austrian chemist, Carl Auer von Welsbach took up the challenge and in June 1885 he succeeded in splitting didymium into its two components, neodymium and praseodymium, which he obtained as their oxides.
A pure sample of praseodymium metal itself was first produced in 1931.
| Atomic radius, non-bonded (Å) | 2.40 | Covalent radius (Å) | 1.90 |
| Electron affinity (kJ mol−1) | 92.819 |
Electronegativity (Pauling scale) |
1.13 |
|
Ionisation energies (kJ mol−1) |
1st
528.064
2nd
1017.92
3rd
2086.399
4th
3761
5th
5550.8
6th
-
7th
-
8th
-
|
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| Common oxidation states | 4, 3 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 141Pr | 140.908 | 100 | - | - | |
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Specific heat capacity (J kg−1 K−1) |
193 | Young's modulus (GPa) | 37.3 | |||||||||||
| Shear modulus (GPa) | 14.8 | Bulk modulus (GPa) | 28.8 | |||||||||||
| Vapour pressure | ||||||||||||||
| Temperature (K) |
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| Pressure (Pa) |
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| Listen to Praseodymium Podcast |
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Transcript :
Chemistry in its element: praseodymium (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, two for the price of one this week. Here's Andrea Sella. Andrea Sella As a graduate student I used to seal off NMR samples under vacuum. As the glass was heated by the torch, the flame would blaze with the fierce orange glow of the sodium lurking in the pyrex. It was all the glassblowing I could do. Anything more serious required a trip down to the ground floor to see our wizard glassblower, Geoffrey Wilkinson, a lovable rogue from the Black Country with an infectious laugh, and wit was as sharp as a razor. One day, as he stood at his lathe with an orange inferno raging before him I asked him about the glasses he was wearing. "Didymium" he answered cryptically, and then noticing my blank look, he added "Cuts out the light. Try them." He passed me his specs, the lenses of a curious greeny-grey colour. I slipped them on and suddenly the flame was gone. All I could see was a red-hot piece of spinning glass unobscured by the glare. I gawped in wonder until Geoff pulled the specs off my face saying "Give 'em back ya fool" and went back to his work. Didymium is not a name you will often find in textbooks these days. It is the name of a pair of elements which lie next to each other in the lanthanide or rare earth series - what used to be the Wild West of the periodic table. The fourteen elements that constitute the series are remarkable for their similarity. Nowhere else does one find a group of elements that so resemble each other in their chemical properties. Hence these elements proved incredibly difficult to separate from each other and purify. And to make matters worse, unlike other metals, the colours of rare earth metal compounds were pale changed little from one compound to the next, making it even harder to work out whether your material was pure. Amongst the many claims for the discovery of new elements was a report in 1839 by the Swedish chemist Carl Gustav Mosander of a supposed element he called "Didymium" - after the Greek word for twin. The invention of spectroscopy by Gustov Kirchoff and Robert Bunsen (yup, he of the Bunsen burner) now came into its own. It was soon realized that the spectre of the rare earths were very characteristic, with sharp gas-phase-like lines both in the solid and solution. At last there was a means of establishing purity. Bunsen, who, by the 1870s, was the world's leading authority on the spectroscopy of the rare earths set this element as a problem for one of his students Carl Auer, who began to carry out the hundreds of fractional crystallizations necessary to get it pure. By 1885 it was clear that Auer had not one but two elements on his hands - a bluish lilac one he called "Neodymium", the new twin - and a green one he named "Praseodymium" - the green twin, each with their own spectra which summed together were the same as those of Mosander's material. Bunsen was delighted and immediately gave his approval to his student's work. But it would not be until the 1940s before fast and effective methods for the separation of the lanthanides would be developed. Rather than the series of excruciatingly tedious crystallizations, the American chemists led by Frank Spedding described ion exchange methods and then within a few years solvent extraction became prevalent and produced kilogram quantities of these elements. Suddenly, commercial applications became a real prospect. Because the ions themselves have unpaired electrons, their magnetic properties have proved fascinating to scientists and lucrative to entrepreneurs. An alloy of neodymium, iron and boron discovered in the 1980s is ferromagnetic, yielding permanent magnets over 1000 times stronger than anything ever seen before. Neodymium ion borade magnets have not only found their way into almost billions of electric motors and electronic devices around the world but also into wonderful toys for children. On the other hand, the sharp spectral lines that so fascinated Bunsen and generations of spectroscopists since, imply very precise electronic states. Embedding neodymium into synthetic gemstones such as garnet resulted in the Neodymium:YAG laser, the workhorse of industrial laser cutting tools with its brilliant infrared lines. Your personalised iPod was probably engraved with a YAG. Coupled with a frequency doubling crystal a YAG gives us the bright green laser pointer than some lecturers like to show off with. But some lateral thinking in the 1940s by chemists at Corning Glassworks in the US gave the invention that changed glassblowing forever. Someone spotted that both praseodymium and neodymium had absorption lines corresponding almost exactly with that annoyingly brilliant orange sodium line. Corning began producing "Didymium glass" which acts as an optical notch filter to cut out the glare and effect remains as astonishing to me today as it was the first time I saw it. When, a few years ago, one of our glassblowers here at UCL retired, he phoned me up on his last day. "I have something for you," he said mysteriously. I went down to the basement and shook his hand to wish him well. And then, to my delight, he handed me his specs. "Didymium," he said, "You'll need these." Chris Smith Andrea Sella with the story of didymium, two elements rolled into one. And Andrea is back next week with a taste of a metal that melts in your mouth and possibly also in your hands. Andrea Sella But I'm sure you really want to know is, if this really is the M & M element, what does it taste like? I knew you would ask. So I had a quick lick a couple of days back and the answer is it doesn't actually taste of very much to be honest. There's a faintly astringent and metallic taste which lingers on your tongue for few hours. And when it is molten, sorry I'll leave that experiment for someone more intrepid than I. Chris Smith And you can catch the story of gallium, which is what he was eating, with Andrea Sella on next week's Chemistry in its element, that's of course assuming that his element eating antics haven't poisoned him in the meantime. I'm Chris Smith, thank you for listening and goodbye. (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.
