in your element Unsporting scandium From Earth to the stars and back again, John Emsley surveys the uses, occurrences and mysteries of an element that is playing an increasing role in human affairs.

hen Dimitri Mendeleev first melting point by 800 °C so that, unlike presented his periodic table ordinary aluminium, it can be welded. Win 1869, he did so noting that Russia has even stockpiled scandium for there were larger than expected differences strategic reasons because several parts for between the atomic weights of several advanced MiG jet fighters (pictured) are elements, and left gaps for them. One such manufactured from this alloy. Meanwhile gap was between calcium and titanium, in the USA, scandium alloys are often and from this he speculated that there used to make sports equipment such as should exist a metal with an atomic baseball bats, lacrosse sticks and bicycle weight of approximately 44 — which frames. It was also discovered that using he called ‘ekaboron’. Just ten years later, such alloys to make cricket bats also

Lars Fredrik Nilson at the University of ZABIELIN/ALAMY © OLEG improved their hitting power, but this was Uppsala was analysing the brown lustrous deemed ‘unsporting’ and scandium was mineral euxenite — which actually used these spectra to report that scandium immediately banned. contains no fewer than eight metals — is, unexpectedly, more abundant in other The primary form of refined scandium,

when he found that a metal extracted from stars than in our Sun. This stellar anomaly the oxide, Sc2O3, also has a few specialized it exhibited lines in its atomic spectrum is still being studied, as is a curious uses, even though world production that had not been previously reported. This scandium-rich nebula that surrounds amounts to only a few tonnes per year metal, whose atomic weight he calculated the Eta Carinae star system 8,000 light — and even less is converted to the to be 44, was indeed the missing element years away. It has been observed over metal itself. Scandium oxide provides a anticipated by Mendeleev. Ekaboron is the centuries to brighten and dim quite specialized optical coating for UV detectors2, not to be found in modern-day periodic inexplicably1, and the role of scandium in transparent to wavelengths between 0.25– tables though, as Nilson named his newly this observation is still under investigation. 5.0 μm, and is also used in neutron filters for discovered element ‘scandium’ after the Although its function and fate in nuclear reactors. Latin for Scandinavia. interstellar space has yet to be clarified, Other potential uses of scandium On Earth, scandium is not particularly scandium has no role in the biosphere continue to be found. It is added to mercury abundant, and is found in similar quantities on Earth, and no living organism has vapour lamps to create a softer glow more to lead. Unlike lead, however, it is widely yet been found that requires it. Only akin to sunlight, and these lamps are dispersed throughout the Earth’s crust minute traces of scandium enter the often used in floodlights at sports venues. because there are no geological processes food chain and the average person’s daily Scandium complexes show potential as to concentrate it, which is why it is present intake is likely to be less than a tenth of hydroamination catalysts3, and scandium in small amounts in hundreds of minerals. a microgram. Rather strangely, tea leaves sulfate does likewise as a seed germinating Minerals made purely of scandium contain comparatively more scandium agent. Whether these applications of compounds are highly prized by collectors. than other plants — although, as this scandium become as prized as its use in Samples of the greenish-black thortveitite is on average only 140 ppb, tea lovers fighter jets or as frowned upon as its use

(Sc2Si2O7) from Iveland in Norway were need not be concerned. One explanation cricket bats remains to be seen. ❐ worth more than their weight in gold for this unusual concentration is that at some points during the 1950s, and a tea bushes do not discriminate between JOHN EMSLEY is a science writer and specimen less than 10 cm in length is absorbing chemically similar aluminium author of Nature’s Building Blocks and currently on the market for $1,500. There — which they are known to require — other books. are samples of thortveitite of such crystalline and scandium. e-mail: [email protected] purity that they have been cut as gem stones, Even though there are no scandium which may explain why similar specimens mines, and so it is only extracted as a References fetch such a high price. by-product of tantalum and uranium 1. Bautista, M. A. et al. Mon. Not. R. Astron. Soc. 393, 1503–1512 (2009). The strong lines in the atomic spectrum mining, scandium is still valued for use 2. Rainer, F. et al. App. Opt. 21, 3685–3688 (1982). that enabled Nilson to first identify in alloys with aluminium. Adding 0.5% 3. Lauterwasser, F. et al. Organometallics 23, 2234–2237 (2004). scandium also allow its relative abundance scandium to aluminium greatly increases in stars and the interstellar medium to the metal’s strength while maintaining be probed. In 1908, Sir William Crookes its light weight, as well as raising its Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr NATURE CHEMISTRY | VOL 6 | NOVEMBER 2014 | www.nature.com/naturechemistry 1025

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