Themes

Ytterbium: structure, properties, uses, obtaining

It dissolves quickly in concentrated and dilute acids, releasing hydrogen. But it is not dissolved by hydrofluoric acid, with which it forms a protective layer on the metal surface. Ytterbium is the lanthanide with the lowest boiling point .

Ultrapure and metallic sample of ytterbium. Source: Hi-Res Images of Chemical Elements, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

Ytterbium was discovered in 1878 by the Swiss chemist Jean Charles Galissard de Marignac. Galissard heated erbium nitrate, obtaining an unknown white powder that he called ytterbia and suspected that it was the compound of a new element that he named “ytterbium” after the Swedish village of Ytterby.

Ytterbium is a metal with few applications, one of them being a doping of stainless steel.

Structure

Ytterbium has three allotropic forms: the α phase, predominantly below 7ºC and whose crystalline structure is compact hexagonal (hcp); the β form, existing at room temperature and with a face-centered cubic structure (fcc); and the γ phase, generated at high temperatures (795 ºC) and with a cubic structure centered in the body.

In the β phase, ytterbium behaves like a metallic electrical conductor, but its resistivity and electrical resistance increase under very high pressures (16 GPa or 16000 atm).

Electronic configuration

Ytterbium has the following electronic configuration:

[Xe] 4f 14 6s 2

As can be seen, all its 4f orbitals are filled with electrons, being almost at the end of the lanthanide series. As they do not have electrons in their 5d orbitals, and there is no electronic vacancy in their atoms, it is likely that these are the reason why their physical properties ( density and melting point) differ from those of their congeners or the other lanthanides.

Ytterbium properties

99.9% ytterbium

Physical appearance

Glossy white metal with pale yellow tint. It is soft, malleable and ductile. Its shine slowly tarnishes when exposed to air and moisture.

Atomic number

70

Molar mass

173.045 g / mol

Melting point

824 ° C.

Boiling point

1196 ° C. It has the lowest boiling point among the lanthanides, which is why it is considered the most “volatile”.

6.90 g / cm 3 (α phase)

6.96 g / cm 3 (β phase)

6.57 g / cm 3 (γ phase)

Heat of fusion

7.66 kJ / mol

Heat of vaporization

129 kJ / mol

Molar caloric capacity

26.74 J / (mol K)

Oxidation states

Ytterbium has the following oxidation states: +1 (Yb + ), +2 (Yb 2+ ) and +3 (Yb 3+ ), the latter being the most predominant, like almost all other lanthanides.

Electronegativity

1.06 on Alfred Rochow scale

Ionization energies

First: 603.4 kJ / mol

Second: 1174.8 kJ / mol

Third: 2417 kJ / mol

Magnetic order

Ytterbium is paramagnetic above 1 K. It has the lowest magnetic susceptibility among rare earth metals.

Compounds and reactivity

In most of its compounds, ytterbium uses its +3 oxidation state, although in some cases it uses the +2 oxidation state. Ytterbium is a reactive element that reacts slowly with cold water, but quickly with hot water, causing hydroxide and hydrogen:

2 Yb (s) + 6 H 2 O (l) → 2 Yb (OH) 3  (aq) + 3 H 2  (g)

Ytterbium is easily dissolved by acids with the release of hydrogen. It also reacts with hydrogen to form various hydrides (YbH x ). Ytterbium combines with halogens to form halides, using its 3+ oxidation state (YbF 3 , YbCl 3 , etc.).

The ytterbium ion Yb 3+ is colorless like ytterbium (Yb 2 O 3 ) and the salts it forms. However, the Yb 2+ ion is greenish-yellow in color and is a highly reactive agent that forms pale green salts with sulfate, bromide, and carbonate.

Ytterbium powder can burn at a temperature of 400ºC, emitting toxic smoke.

Applications

Doping action

Ytterbium is used as a doping agent for stainless steel in order to improve its strength, grain refinement, and mechanical properties.

In double-coated fiber and disk lasers, Yb 3+ ions are used as dopants for optical fibers, as in crystals and ceramics.

Dental

Ytterbium is part of Retroplast, a composite resin that adheres to dentin. Retroplast is a mixture of two components A and B, with ytterbium trifluoride being part of component B.

Ground shake detection

Ytterbium has the property of increasing its electrical resistance by increasing the pressure it experiences to very high values, such as what occurs in earthquakes and underground explosions. Therefore, electrical circuits that include ytterbium can be used in order to detect earth shaking.

X-ray source

The isotope of ytterbium 69 Yb is used as a source of gamma radiation, which has properties similar to X-rays, with regard to its penetrating power. For this reason, the 69-isotope of ytterbium is used as a portable X-ray source in places lacking electricity, usable on small objects.

Solar cells

Ytterbium has an absorption band in the infrared part of the electromagnetic spectrum, which is why it is used in solar cells to convert infrared radiation into electricity.

Obtaining

Ytterbium is present in the minerals monazite, euxenite and xenotime, presenting an estimated abundance in the earth’s crust of 3 ppm. The first step is the crushing of the mineral, generally monazite, then the rare earth elements are leached with sulfuric acid and other acids.

The neutralized solution is placed in contact with an exchange resin, the elements of the rare earth being united to it when interacting with chemical groups present in the resin. Then, the ytterbium is separated from the resin by using a specific complexing substance.

Another method of obtaining ytterbium is by reducing it with a sodium-mercury amalgam. This amalgam is then treated with hydrochloric acid, extracting the metal with oxalate and turning it into its oxide by heating.

Finally, metallic ytterbium is obtained from its oxide by carrying out its reduction by heating in the presence of zirconium, aluminum or other elements, to finally be purified by sublimation.

Isotopes

Ytterbium has a total of 34 isotopes: 7 stable and 27 radioactive. The group of stable isotopes is made up of 168 Yb, 170 Yb, 171 Yb, 172 Yb, 173 Yb, 174 Yb, and 176 Yb, of which the isotope 174 Yb is found in the highest proportion , with 31.896 % abundance.

The radioactive isotope 169 Yb has the longest half-life (32,026 days), while the rest of the radioactive isotopes have a short or very short half-life.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button