|Group||2||Melting point||777 oC, 1431 oF, 1050 K|
|Period||5||Boiling point||1377 oC, 2511 oF, 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|
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.
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.
Specific heat capacity
(J kg-1 K-1)
|306||Young's modulus (GPa)||Unknown|
|Shear modulus (GPa)||Unknown||Bulk modulus (GPa)||Unknown|
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.
|Listen to Strontium Podcast|
Chemistry in Its Element - Strontium
You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry.
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.
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.
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!
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!
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 web site at chemistryworld dot org forward slash elements.
© Murray Robertson 2011.
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 3.0), 2010, National Institute of Standards and Technology, Gaithersburg, MD, accessed December 2014.
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.
© John Emsley 2012.
Produced by The Naked Scientists.
Periodic Table of Videos
Created by video journalist Brady Haran working with chemists at The University of Nottingham.