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History

The mineral gadolinite, (Ce, La, Nd, Y)₂FeBe₂Si₂O₁₀, discovered in a quarry near the town of Ytterby, Sweden, has been the source of a great number of rare earth elements.  In 1843, Carl Gustaf Mosander, a Swedish chemist, was able to separate gadolinite into three materials, which he named yttria, erbia and terbia.   As might be expected considering the similarities between their names and properties, scientists soon confused erbia and terbia and, by 1877, had reversed their names.  What Mosander called erbia is now called terbia and visa versa. 

In 1878 Jean Charles Galissard de Marignac, a Swiss chemist, discovered that erbia was itself consisted of two components.  He suspected that ytterbia was a compound of a new element he called ytterbium.  Initial identification was tediously made from the same mixture that most chemists of the time worked from: oxides of the lanthanides which gave rise to the term "rare-earth" due to its powdery consistency and often brownish color.  But with the chemical separation techniques available at the time, it was very difficult to distinguish these similar elements.  Even ytterbium itself turned out to hide another element. One component was named ytterbia by Marignac while the other component retained the name erbia.  Marignac believed that ytterbia was a compound of a new element, which he named ytterbium.  Other chemists produced and experimented with ytterbium in an attempt to determine some of it's properties.  Unfortunately, different scientists obtained different results from the same experiments. 

While some scientists believed that these inconsistent results were caused by poor procedures or faulty equipment, Georges Urbain, a French chemist, believed that ytterbium wasn't an element at all, but a mixture of two elements.  I n 1907, Urbain was able to separate ytterbium into two elements.  Urbain named one of the elements neoytterbium (new ytterbium) and the other element lutecium.  Chemists eventually changed the name neoytterbium back to ytterbium and changed the spelling of lutecium to lutetium.  Due to his original belief of the composition of ytterbia, Marignac is credited with the discovery of ytterbium.  Even ytterbium itself turned out to hide another element.

Austrian mineralogist Baron Carl Auer von Welsbach independently isolated these elements from ytterbia at about the same time but called them aldebaranium and cassiopeium.

The chemical and physical properties of ytterbium could not be determined until 1953 when the first nearly pure ytterbium was produced.

Characteristics

Ytterbium is a soft, malleable and rather ductile element that exhibits a bright silvery lister.  A rare earth element, it is easily attacked and dissolved by mineral acids, slowly reacts with water, and oxidizes in air.  Mostly obtained from monazite sand, ytterbium makes up about 0.03% of that mixture.

Ytterbium has three allotropes which are called alpha, beta and gamma and whose transformation points are at -13°C and 795 °C. The beta form exists at room temperature and has a face-centered crystal structure while the high-temperature gamma form has a body-centered crystal structure.

Normally, the beta form has a metallic-like electrical conductivity, but becomes a semiconductor when exposed to around 16,000 atm (1.6 GPa).  Its electrical resistance is tenfold larger at about 39,000 atm (3.9 GPa) but then dramatically drops to around 10% of its room temperature resistivity value at 40,000 atm (4 GPa).

Occurrence

Ytterbium is found with other rare earth elements in several rare minerals.  It is most often recovered commercially from monazite sand (~0.03% ytterbium). The element is also found in euxenite and xenotime.  Ytterbium is normally difficult to separate from other rare earths but ion-exchange and solvent extraction techniques developed in the late 20th century have simplified separation.  Known compounds of ytterbium are rare—they haven't been well characterized yet.

Applications

One ytterbium isotope has been used as a radiation source substitute for a portable X-ray machine when electricity was not available.  Its metal could also be used to help improve the grain refinement, strength, and can be alloyed with stainless steel to improve some of its mechanical properties and used as a doping agent in fiber optic cable where it can be used as an amplifier.  Some ytterbium alloys have been used in dentistry.  here are few other uses of this element, e.g. in the form of ions in active laser media.

Isotopes

Naturally occurring ytterbium is composed of 7 stable isotopes, Yb-168, Yb-170, Yb-171, Yb-172, Yb-173, Yb-174, and Yb-176, with Yb-174 being the most abundant (31.8% natural abundance).  27 radioisotopes have been characterized, with the most stable being Yb-169 with a half-life of 32.026 days, Yb-175 with a half-life of 4.185 days, and Yb-166 with a half life of 56.7 hours.  All of the remaining radioactive isotopes have half-lifes that are less than 2 hours, and the majority of these have half lifes that are less than 20 minutes.  This element also has 6 meta states, with the most stable being Yb-169m (t_½ 46 seconds).

The isotopes of ytterbium range in atomic weight from 147.96742 amu (¹⁴⁸Yb) to 180.95615 amu (¹⁸¹Yb).  The primary decay mode before the most abundant stable isotope, Yb-174 is electron capture, and the primary mode after is beta emission.  The primary decay products before Yb-174 are element thulium-69 isotopes, and the primary products after are element lutetium-71 isotopes.  Of interest to modern quantum optics, the different ytterbium isotopes follow either Bose-Einstein statistics or Fermi-Dirac statistics, leading to interesting behavior in optical lattices.

Precautions

Although ytterbium is fairly stable, it nevertheless should be stored in closed containers to protect it from air and moisture. All compounds of ytterbium should be treated as highly toxic although initial studies appear to indicate that the danger is limited. Ytterbium compounds are, however, known to cause skin and eye irritation and may be teratogenic.  Metallic ytterbium dust poses a fire and explosion hazard.