The most important village in chemistry

In your class

From people and places to mythology, the etymology of elemental names is fascinating and can provide an opportunity to weave some storytelling into chemistry lessons. Often we concentrate on the names that originate in antiquity, this article provides flavour to a lesson about more recent discoveries. It makes an excellent context for lessons on atomic structure and isotopes.

It’s a damp day in Ytterby. The bus arrives at the edge of town, bringing commuters back home from nearby Stockholm before turning around again; the village is the end of the line. A few souls leave their picturesque cottages to brave the wet and walk their dogs, heading along the streets to Ytterby’s only shop. Through the trees, you can just make out boats bobbing quietly at anchor on waters of the archipelago. It seems to be the kind of village where nothing happens.

Until, that is, you notice the street signs. Translated from Swedish, they are all named after chemical elements: ytterbium road, terbium road, tantalum road. It may seem quiet, but Ytterby is one of the most important spots in scientific history. It is the richest source of naturally occurring elements on Earth.

His dark minerals

In 1789, a 30-year-old Swedish artillery lieutenant, Carl Axel Arrhenius, was exploring Ytterby and the nearby islands to identify a spot for a new fort. Arrhenius was interested in minerals and decided to visit the village’s mine, which supplied Stockholm with feldspar that was used in making porcelain and glass. There, Arrhenius noticed a strange, heavy black rock he didn’t recognise.

Arrhenius called the rock ytterbite and eventually sent it off to the lab of his friend Johan Gadolin, a chemistry professor at the Royal Academy of Turku in Finland (then part of Sweden). Analysing the strange rock, Gadolin soon realised almost 40% of it was made from a metal that had never been seen before. He called his discovery a ‘rare earth’ and sent it on to another chemist, Anders Gustaf Ekeberg, to confirm his results. Ekeberg named the oxide of new element ‘yttria’ and renamed ytterbite ‘gadolinite’.

Ytterby might be a small village, but it’s had a big impact on our world

The discovery was a sensation. For the next 120 years, chemists would continue to isolate new metals from the rock. But it turned out the rare earths were all very similar, which made splitting them apart very difficult. By 1906, the black mineral had been found to contain nine new elements, most of which were named after the village: yttrium; erbium, terbium, ytterbium, scandium (after Scandinavia); thulium (after thule, the mythical Greek name for Scandinavia); holmium (after Stockholm); dysprosium (‘hard to get’) and lutetium (after the Latin name for Paris, where it was finally isolated). Another sample of a similar black ore was found to contain yet another element, which was called gadolinium.

These elements were important discoveries, especially because their existence provided evidence in favour of other chemical theories. In 1869, the Russian chemist Dimitri Mendeleev had created a version of the periodic table that would lead to the one we use today. Mendeleev used the table to predict the properties of elements, and if something didn’t match up he left a gap. As more of the ‘rare earths’ were discovered, the gaps in Mendeleev’s table began to fill, confirming that the periodic table was real.

The mine today

The climb up to the Ytterby mine is steep. From the road, you must walk up a flight of wooden steps, which cut straight up a steep hill. At the top, a small metal plaque informs you that this is the Ytterby mine where Arrhenius found his black rock. If the plaque wasn’t there, you could easily walk past it: the mine isn’t there.

All that’s left of the Ytterby mine is a small ravine, about 15 metres long and five metres wide – the size of a school classroom. The mineshaft has been completely sealed. After Arrhenius’ discovery, the feldspar continued to be mined there until 1933. Then, the Swedish military used it to store jet fuel. By 1995 the mine had been completely emptied and was closed for good.

Today, we know there are 17 rare earths. Most of them are found at the bottom of the periodic table, away from the rest of the elements, in a row called the lanthanides. Although the mine is sealed, the discoveries made from Arrhenius’ black rock continue to be used around the world. As it turns out ‘rare earths’ aren’t rare at all, and they are mined as part of an international, multibillion pound trade. Yttrium and terbium are important in electronics – yttrium helps create the colour red in TV screens and is used in superconductors, while terbium is used to make green, sonar systems and solid state computer parts. Others are used in lasers, oil refineries, or to improve the strength of stainless steel.

Ytterby might be a small village, but it’s had a big impact on our world.

Article by Kit Chapman, comment editor for Chemistry World, based in Cambridge, UK. Teaching resource by Kristy Turner, a school teacher fellow at University of Manchester/Bolton School, UK