Tag Archives: chemistry

What do Y, Yb, Tb, Er, Gd, Tm, Sc, Ho, Dy and Lu have in common?

What do the following ten elements have in common?

  • Yttrium
  • Ytterbium
  • Terbium
  • Erbium
  • Gadolinium
  • Thulium
  • Scandium
  • Holmium
  • Dysprosium
  • Lutetium

The answer (and there is a tiny clue in some of the names) is that all ten elements were isolated from one sample, taken from a mine in the small village of Ytterby in Sweden. All of the elements are rare earth metals which occur in similar locations and have similar properties. This makes their extraction and isolation very difficult and this is where the “rare” in their name comes from.

In 1787 one of the students of Lieutenant Carl Axel Arrhenius found a dark-coloured ore that was much too heavy to be coal. Arrhenius took this ore, which he named “ytterbite”, and sent samples to various chemists for analysis. One of these chemists, Johan Gadolin, determined that ytterbite did indeed contain a previously unknown element and called this element yttrium.

In 1843 Carl Gustav Mosander demonstrated that ytterbite was actually made of three metal oxides, not one as Gadolin had thought. The original name was kept for one of these three parts and the other two elements named terbium and erbium, both after the village of Ytterby where they were found.

Terbium was later demonstrated to be a mixture of terbium and a new element which was named gadolinium in honour of Gadolin. Erbium was demonstrated to be a mixture of erbium and and a new element which was named ytterbium, again after the village of Ytterby.

Erbium was then itself demonstrated to a mixture of three elements: erbium; thulium, named after Thule, a term used by early map makers for the far north where Sweden is located; and holmium, named after the Swedish capital Stockholm. Holmium was then later demonstrated to be a mixture of holmium and dysprosium, which takes its name from the Greek word dysprositos meaning “difficult to get”, reflecting the difficulty found in isolating it.

Ytterbium was demonstrated to be composed of ytterbium and a new element which was named scandium after Scandanavia, and finally ytterbium was split again to yield ytterbium and lutetium.

A diagram showing the order in which the ten elements were isolated.

How to hide a Nobel medal

In the run up to World War II Niels Bohr’s Institute in Copenhagen had become a refuge for Jewish physicists. The Jewish physicist James Franck and the anti-Nazi physicist Max von Laue, concerned for their gold Nobel Prize medals, both left them there for safekeeping. When Hitler’s army invaded Denmark, Bohr was worried that the invading German soldiers would steal the medals but his friend, the Hungarian physicist George de Hevesy, came up with an ingenious solution.

de Hevesy dissolved both medals in aqua regia, a highly corrosive 1:3 mixture of nitric acid and hydrochloric acid. This formed a transparent yellow liquid, chloroauric acid, that he hid in plain site, simply leaving the jar on a shelf in the Niels Bohr Institute.

When he returned in 1945, after World War II had ended, the jar was still there. The gold was recovered from solution and the medals were restruck by the Nobel Foundation and returned to their rightful owners.