| Discovery date | 1790 |
| Discovered by | Adair Crawford |
| Origin of the name | Strontium is named after Strontian, a small town in Scotland. |
| Allotropes |
|
Sr
Strontium
38
87.62
| Group | 2 | Melting point | 777°C, 1431°F, 1050 K |
| Period | 5 | Boiling point | 1377°C, 2511°F, 1650 K |
| Block | s | Density (g cm−3) | 2.64 |
| Atomic number | 38 | Relative atomic mass | 87.62 |
| State at 20°C | Solid | Key isotopes | 86Sr, 87Sr, 88Sr |
| Electron configuration | [Kr] 5s2 | CAS number | 7440-24-6 |
| ChemSpider ID | 4514263 | ChemSpider is a free chemical structure database | |
Image explanation
The image is of a highly abstracted metallic ‘mushroom cloud’. It alludes to the presence of strontium in nuclear fallout.
Appearance
A soft, silvery metal that burns in air and reacts with water.
Uses
Strontium is best known for the brilliant reds its salts give to fireworks and flares. It is also used in producing ferrite magnets and refining zinc.
Modern ‘glow-in-the-dark’ paints and plastics contain strontium aluminate. They absorb light during the day and release it slowly for hours afterwards.
Strontium-90, a radioactive isotope, is a by-product of nuclear reactors and present in nuclear fallout. It has a half-life of 28 years. It is absorbed by bone tissue instead of calcium and can destroy bone marrow and cause cancer. However, it is also useful as it is one of the best high-energy beta-emitters known. It can be used to generate electricity for space vehicles, remote weather stations and navigation buoys. It can also be used for thickness gauges and to remove static charges from machinery handling paper or plastic.
Strontium chloride hexahydrate is an ingredient in toothpaste for sensitive teeth.
Biological role
Strontium is incorporated into the shells of some deep-sea creatures and is essential to some stony corals. It has no biological role in humans and is non-toxic. Because it is similar to calcium, it can mimic its way into our bodies, ending up in our bones.
Radioactive strontium-90, which is produced in nuclear explosions and released during nuclear plant accidents, is particularly dangerous because it can be absorbed into the bones of young children.
Natural abundance
Strontium is found mainly in the minerals celestite and strontianite. China is now the leading producer of strontium. Strontium metal can be prepared by electrolysis of the molten strontium chloride and potassium chloride, or by reducing strontium oxide with aluminium in a vacuum.
In 1787, an unusual rock which had been found in a lead mine at Strontian, Scotland, was investigated by Adair Crawford, an Edinburgh doctor. He realised it was a new mineral containing an unknown ‘earth’ which he named strontia. In 1791, another Edinburgh man, Thomas Charles Hope, made a fuller investigation of it and proved it was a new element. He also noted that it caused the flame of a candle to burn red.
Meanwhile Martin Heinrich Klaproth in Germany was working with the same mineral and he produced both strontium oxide and strontium hydroxide.
Strontium metal itself was isolated in 1808 at the Royal Institution in London by Humphry Davy by means of electrolysis, using the method with which he had already isolated sodium and potassium.
| Atomic radius, non-bonded (Å) | 2.49 | Covalent radius (Å) | 1.90 |
| Electron affinity (kJ mol−1) | 4.631 |
Electronegativity (Pauling scale) |
0.95 |
|
Ionisation energies (kJ mol−1) |
1st
549.47
2nd
1064.243
3rd
4138.26
4th
5500
5th
6908.4
6th
8760.9
7th
10227
8th
11800.2
|
||
| Common oxidation states | 2 | ||||
| Isotopes | Isotope | Atomic mass | Natural abundance (%) | Half life | Mode of decay |
| 84Sr | 83.913 | 0.56 | - | - | |
| 86Sr | 85.909 | 9.86 | - | - | |
| 87Sr | 86.909 | 7 | - | - | |
| 88Sr | 87.906 | 82.58 | - | - | |
|
|
|
Specific heat capacity (J kg−1 K−1) |
306 | 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 Strontium Podcast |
|
Transcript :
Chemistry in its element: strontium(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, vegetarian gladiators, red fireworks and a mineral mistaken for barium; they are all under strontium's spotlight. Here's Richard Van Noorden. Richard Van Noorden In 1787, an intriguing mineral came to Edinburgh from a Lead mine in a small village on the shores of Loch Sunart, Argyll, in the western highlands of Scotland. At that time, the stuff was thought to be some sort of Barium compound. It was three year's later that Scott's Irish chemist, Adair Crawford, published a paper claiming that the mineral held a new species including a new chemical element. Other chemists, such as Edinburgh's Thomas Hope later prepared a number of compounds with the element, noting that it caused the candle's flame to burn red, while Barium compounds gave a green colour. And in 1808, Humphry Davy in London isolated the soft, silvery metal of the new element using electrolysis. The Scottish village was called Strontian, the mineral found there, strontianite and the new element strontium. So, it seems there never was an eminent professor, Stront, commemorated by element number 38. Today, whenever you see a firework light up in brilliant crimson or a red flare smoking its way around a football stadium, you're looking at the light emitted from electrons transiting between energy levels in nitrate or carbonate salts as strontium. Strontium is most famous for that red glow in a flame, but as a metal it behaves like its reactive group II neighbours, beryllium, magnesium, calcium and barium. It's soft and silvery when freshly cut, but this sheen quickly turns yellow when exposed to air, as the metal readily reacts to form oxides; unlike other reactive alkaline earth metals, natural strontium is always found locked away in mineral compounds. Apart from the previously mentioned strontianite, which we know as strontium carbonate, there is also the beautiful sky blue celestite, strontium sulphate, which was discovered in Gloucestershire in 1799, where the locals were using it as gravel for paths in ornamental gardens. Apart from colouring fireworks, we don't have much call nowadays for strontium compounds. Strontium carbonate notably is found in cathode ray tubes in old television sets. One of strontium's isotopes Strontium-90 has a more sinister reputation. It's a radioactive beta emitter, produced by nuclear fission with a half-life of 29 years. Created by nuclear tests from 1945 to the early 1970s, strontium-90 made its way from the air to grassland, cow stomachs, dairy products and as 1950's studies showed into children's milk teeth. It collects in bones too, being of a similar size to its group II neighbour, calcium ions. The nuclear reactor accident at Chernobyl in 1986 also threw strontium-90 into the air. Nowadays, it's used as a radioactive tracer in cancer therapy. Still strontium's close relation to calcium has made it a modern treatment for treating osteoporosis as the salt strontium ranelate, using non-radioactive isotopes, of course. Because strontium ions are roughly the same size as calcium ions, they bind tightly to calcium sensing receptors. It seems that this stimulates the formation of new bones and prevents old bone from being broken down. And tracing strontium isotope levels in bone has allowed analytical chemists to come up with all sorts of conclusions about our past ancestor's diets, knowing that plants tend to be higher in natural strontium than meat. In 2007, for instance, Austrian researchers hit headlines by comparing strontium and zinc levels to support the hypothesis that Roman gladiators were vegetarians who ate mainly barley, beans and dried fruits. Chris Smith Chemistry World's Richard Van Noorden wrestling gladiator style with the story of strontium. Next time, we've heard of running through treacle, but what about this proposition. Fred Campbell Could a man walk across a swimming pool filled with Mercury? Don't ask me how the conversation had reached this point, but being surrounded by friends, who would, it is fair to say, describe themselves as science illiterate, I knew it was up to me, the token scientist around the table, to give the definitive answer. "No." I confidently said, adding rather smugly, "it is nowhere near dense enough." The next morning I was rudely awakened by my ringing mobile; not for the first time, I was wrong! Chris Smith And you can find out exactly how wrong Fred Campbell was at his dinner party when he unlocks the chemical secrets of quick silver, otherwise known as mercury on next week's Chemistry in its element. I hope you can join us. I'm Chris Smith, thanks for listening. 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.
