Ytterbium – facts and properties

Position in the periodic table

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Occurrence and extraction

Ytterbium counts among the heavy rare earths covered on the lanthanum page. In the Earth's crust it is more common than tungsten. It is obtained from xenotime, which holds it in appreciable shares, from monazite and from the ion-adsorption clays of southern China. One peculiarity helps with separation. Like europium and samarium, ytterbium can be converted from the triply charged form into the doubly charged one, for instance by reduction in solution. The divalent ions behave chemically unlike their trivalent neighbours and are therefore easier to split off. Because the metal evaporates easily, the oxide is heated together with lanthanum in a vacuum, and the ytterbium distils off.

In 1878 the Swiss chemist Jean Charles de Marignac heated erbium nitrate and obtained two oxides. One was the familiar erbium oxide, the other was new. He named it ytterbia after the find spot, Ytterby. That puts the name in a row with yttrium, terbium and erbium, and the story of the place is told on the yttrium page. Almost thirty years later it emerged that Marignac's ytterbia was still a mixture, and another element was hiding in it.

Properties and reactions

Ytterbium is the fourteenth and next-to-last lanthanide, and with it the 4f subshell is full. In period 6, thulium is on its left and lutetium on its right. The atom's electron configuration is [Xe] 4f¹⁴ 6s². The metal melts at 819 °C and boils at 1196 °C, both far lower than for its neighbours. The density of 6.9 g/cm³ is lower as well. In air the metal dulls only slowly.

The reason for its special role is the filled 4f subshell. It is so stable that the atom is reluctant to touch it. In the metal each atom therefore contributes only two electrons to the bonding instead of three. The cohesion is weaker, the metal melts earlier, and the atoms need more room, so the density stays low.

Ytterbium can also be divalent in compounds. The Yb²⁺ ion has the filled shell 4f¹⁴ and is more stable than the divalent ions of most lanthanides. It is a strong reducing agent, though: in water it is quickly oxidised to Yb³⁺ and releases hydrogen. The trivalent ion is colourless but absorbs near-infrared light around 980 nanometres, and that is exactly where ytterbium lasers are pumped.

Uses in everyday life and technology

Ytterbium is famous for its clocks. In an optical lattice clock, a grid of laser light holds thousands of ytterbium atoms in place at once. A clock laser with orange-yellow light at 578 nanometres excites an especially sharp transition in the atoms, and its oscillations are counted. Visible light oscillates more than fifty thousand times as often per second as the microwaves in caesium atomic clocks. The best of these clocks are so accurate that over a span as long as the age of the universe they would drift by little more than a second. Such optical clocks are expected to become the basis of a new definition of the second one day.

Commercially, ytterbium fibre lasers matter more. The core of the glass fibre contains Yb³⁺ ions, pump diodes excite them, and the fibre emits laser light at around 1000 nanometres. The devices run efficiently and reach powers of many kilowatts. They cut and weld sheet metal in the car industry, engrave components and melt metal powder in 3D printing. Crystals doped with ytterbium also deliver ultrashort pulses, with which material can be machined almost without heat.

Ytterbium compounds are regarded as slightly toxic.

Quick question

What is the atomic number of ytterbium (Yb)?

FAQ