ytterbium

ytterbium
Number	70
Name	ytterbium
Category	lanthanide
Group	n/a
Standard atomic weight	173.045
Electron configuration	[Xe] 4f14 6s2
Phase	solid
Melting point degC	824
Boiling point degC	1196
Density g cm3	6.90
Oxidation states	+2, +3

ytterbium is a soft, malleable, and ductile chemical element belonging to the lanthanide series. It is a relatively stable metal in air compared to other rare-earth elements but slowly oxidizes, forming a protective surface layer. The element exhibits two common oxidation states, with the +3 state being predominant in aqueous solutions and most of its compounds. Its properties are significantly influenced by its position within the f-block of the periodic table.

Characteristics

Ytterbium is a bright, silvery metal that is both ductile and fairly soft, allowing it to be cut with a knife. It crystallizes in a face-centered cubic structure at room temperature but transforms to a body-centered cubic form upon heating. The element has seven stable isotopes, with ytterbium-174 being the most abundant, and several radioactive isotopes such as ytterbium-169 are used in scientific applications. Its electrical resistivity and magnetic properties are highly sensitive to changes in pressure and temperature, making it a subject of study in condensed matter physics. In its +2 oxidation state, ytterbium behaves similarly to the alkaline earth metals, particularly calcium and strontium, while the +3 state aligns it with other trivalent lanthanides.

History

The discovery of ytterbium is intertwined with the history of other rare-earth elements found in the mineral gadolinite from a quarry near Ytterby, Sweden. In 1878, Swiss chemist Jean Charles Galissard de Marignac isolated a new component from erbium nitrate, which he named ytterbia. Initially, this was believed to be a single element, but in 1907, French chemist Georges Urbain separated ytterbia into two distinct oxides: neoytterbia and lutetia. These corresponded to the elements now known as ytterbium and lutetium, a conclusion contested by Carl Auer von Welsbach and Charles James but ultimately upheld by the International Union of Pure and Applied Chemistry. The first relatively pure metallic ytterbium was produced in 1937 by Wilhelm Klemm and Heinrich Bommer through the reduction of its oxide.

Occurrence and production

Ytterbium is never found in nature as a free element but occurs in several rare-earth minerals. Its primary commercial sources are minerals such as xenotime, monazite, and euxenite, which contain small amounts mixed with other lanthanides. The largest reserves of these minerals are found in deposits in China, the United States, Brazil, India, and Sri Lanka. Industrial production typically involves solvent extraction and ion-exchange chromatography techniques to separate ytterbium from other rare-earth elements after ore digestion with strong acids like sulfuric acid. The metal is then obtained by reducing purified ytterbium fluoride with calcium metal in a tantalum crucible under an inert atmosphere of argon.

Compounds

Ytterbium forms a range of compounds primarily in the +3 oxidation state, including ytterbium(III) oxide, a white solid used in special ceramics and as a doping agent. Ytterbium(III) chloride is a common starting material in organometallic chemistry and serves as a catalyst in organic synthesis. The +2 state is less common but stable in compounds like ytterbium(II) iodide, a strong reducing agent used in research. Ytterbium also forms halides, chalcogenides, and pnictides, many of which exhibit interesting optical and electronic properties studied at institutions like Los Alamos National Laboratory. Organoytterbium compounds are part of ongoing research in the field of lanthanide coordination chemistry.

Applications

One of the most significant uses of ytterbium is as a doping agent in high-power and high-efficiency fiber lasers and solid-state lasers, particularly those operating at wavelengths around one micron. Ytterbium-doped materials are key components in industrial cutting and welding systems. The isotope ytterbium-169 is a gamma-ray source used in portable X-ray machines for non-destructive testing and in certain medical imaging applications. Ytterbium is also employed as an industrial chemical catalyst, notably in the petrochemical industry for hydrocarbon cracking. In scientific research, ytterbium atoms are used in atomic clock experiments at institutions like the National Institute of Standards and Technology to achieve exceptional timekeeping precision.

Precautions

While metallic ytterbium is generally considered to have low toxicity, its compounds should be handled with care as they can be irritants to the skin and eyes. Fine ytterbium powder poses a fire and explosion hazard, as it can ignite spontaneously in air, similar to other pyrophoric metals. There is no known biological role for ytterbium, and soluble ytterbium salts are considered mildly toxic if ingested, potentially affecting the liver. Standard laboratory safety protocols, including the use of personal protective equipment and proper ventilation, are recommended when working with ytterbium materials, as advised by agencies like the Occupational Safety and Health Administration.

Category:Chemical elements Category:Lanthanides