Terbium

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Terbium, 65Tb
Terbium
Pronunciation/ˈtɜːrbiəm/ ​(TUR-bee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Tb)
Terbium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
–
↑
Tb
↓
Bk
gadolinium ← terbium → dysprosium
kJ/mol
Heat of vaporization391 kJ/mol
Molar heat capacity28.91 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1789 1979 (2201) (2505) (2913) (3491)
Atomic properties
Discovery and first isolation
Carl Gustaf Mosander (1843)
Isotopes of terbium
Main isotopes[7] Decay
abun­dance half-life (t1/2) mode pro­duct
157Tb synth 71 y ε
157Gd
158Tb synth 180 y ε
158Gd
β−
158Dy
159Tb 100%
stable
 Category: Terbium
| references

Terbium is a

electropositive metal that reacts with water, evolving hydrogen gas. Terbium is never found in nature as a free element, but it is contained in many minerals, including cerite, gadolinite, monazite, xenotime and euxenite
.

Swedish chemist Carl Gustaf Mosander discovered terbium as a chemical element in 1843. He detected it as an impurity in yttrium oxide, Y2O3. Yttrium and terbium, as well as erbium and ytterbium, are named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques.

Terbium is used to

solid-state devices, and as a crystal stabilizer of fuel cells that operate at elevated temperatures. As a component of Terfenol-D (an alloy that expands and contracts when exposed to magnetic fields more than any other alloy), terbium is of use in actuators, in naval sonar systems and in sensors
.

Most of the world's terbium supply is used in green

trichromatic
lighting technology, a high-efficiency white light used for standard illumination in indoor lighting.

Characteristics

Physical properties

Terbium is a silvery-white

ductile and soft enough to be cut with a knife.[8] It is relatively stable in air compared to the earlier, more reactive lanthanides in the first half of the lanthanide series.[9] Terbium exists in two crystal allotropes with a transformation temperature of 1289 °C between them.[8] The 65 electrons of a terbium atom are arranged in the electron configuration [Xe]4f96s2. The eleven 4f and 6s electrons are valence. Only three electrons can be removed before the nuclear charge becomes too great to allow further ionization, but in the case of terbium, the stability of the half-filled [Xe]4f7 configuration allows further ionization of a fourth electron in the presence of very strong oxidizing agents such as fluorine gas.[8]

The terbium(III) cation is brilliantly

emission line in combination with other lines in the orange and red. The yttrofluorite variety of the mineral fluorite owes its creamy-yellow fluorescence in part to terbium. Terbium easily oxidizes, and is therefore used in its elemental form specifically for research. Single terbium atoms have been isolated by implanting them into fullerene
molecules. Trivalent Eu3+ and Tb3+ ions are among the lanthanide ions that have garnered the most attention because of their strong luminosity and great color purity.[10][11]

Terbium has a simple

paramagnetic state at 230 K.[12]

Chemical properties

Terbium metal is an electropositive element and oxidizes in the presence of most acids (such as sulfuric acid), all of the halogens, and even water.[13]

2 Tb (s) + 3 H2SO4 → 2 Tb3+ + 3 SO2−4 + 3 H2↑
2 Tb + 3 X2 → 2 TbX3 (X = F, Cl, Br, I)
2 Tb (s) + 6 H2O → 2 Tb(OH)3 + 3 H2↑

Terbium also oxidizes readily in air to form a mixed terbium(III,IV) oxide:[13]

8 Tb + 7 O2 → 2 Tb4O7

The most common oxidation state of terbium is +3 (trivalent), such as

TbCl
3. In the solid state, tetravalent terbium is also known, in compounds such as TbO2 and TbF4.[14] In solution, terbium typically forms trivalent species, but can be oxidized to the tetravalent state with ozone in highly basic aqueous conditions.[15]

The coordination and organometallic chemistry of terbium is similar to other lanthanides. In aqueous conditions, terbium can be coordinated by nine water molecules, which are arranged in a tricapped trigonal prismatic molecular geometry. Complexes of terbium with lower coordination number are also known, typically with bulky ligands like bis(trimethyl-silylamide), which forms the three-coordinate Tb[N(SiMe3)2]3 complex.

Most coordination and organometallic complexes contain terbium in the trivalent oxidation state. Divalent (Tb2+) complexes are also known, usually with bulky cyclopentadienyl-type ligands.[16][17][18] A few coordination compounds containing terbium in its tetravalent state are also known.[19][20][21]

Oxidation states

Like most

lanthanides, terbium is usually found in the +3 oxidation state. Like cerium and praseodymium, terbium can also form a +4 oxidation state, although it is unstable in water.[22]
However, it is possible for terbium to also be found in the 0, +1 and +2 oxidation states.

Compounds

Main article: Terbium compounds
Terbium sulfate, Tb2(SO4)3 (top), fluoresces green under ultraviolet light (bottom)

Terbium combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic at elevated temperatures, forming various binary compounds such as TbH2, TbH3, TbB2,

TbN.[23] In those compounds, Tb mostly exhibits the oxidation states +3 and sometimes +2. Terbium(II) halides are obtained by annealing Tb(III) halides in presence of metallic Tb in tantalum containers. Terbium also forms sesquichloride Tb2Cl3, which can be further reduced to TbCl by annealing at 800 °C. This terbium(I) chloride forms platelets with layered graphite-like structure.[24]

Terbium(IV) fluoride is the only halide that tetravalent terbium can form, and has strong oxidizing properties. It is also a strong fluorinating agent, emitting relatively pure atomic fluorine when heated, rather than the mixture of fluoride vapors emitted from cobalt(III) fluoride or cerium(IV) fluoride.[25] It can be obtained by reacting terbium(III) chloride or terbium(III) fluoride with fluorine gas at 320 °C:[26]

2 TbF3 + F2 → 2 TbF4

When TbF4 and CsF is mixed in a stoichiometric ratio, in a fluorine gas atmosphere, CsTbF5 is obtained. It is an orthorhombic crystal, with space group Cmca, with a layered structure composed of [TbF8]4− and 11-coordinated Cs+.[27] The compound BaTbF6 can be prepared in a similar method. It is an orthorhombic crystal, with space group Cmma. The compound [TbF8]4− also exists.[28]

Other compounds include

Isotopes

Main article: Isotopes of terbium

Naturally occurring terbium is composed of its only stable

beta minus decay, resulting in dysprosium isotopes.[29]

The element also has 27 nuclear isomers, with masses of 141–154, 156, and 158 (not every mass number corresponds to only one isomer). The most stable of them are terbium-156m, with a half-life of 24.4 hours, and terbium-156m2, with a half-life of 22.7 hours; this is longer than half-lives of most ground states of radioactive terbium isotopes, except those with mass numbers 155–161.[29]

Terbium-149, with a half-life of 4.1 hours, is a promising candidate in

targeted alpha therapy and positron emission tomography.[30][31]

History

Carl Gustaf Mosander, the scientist who discovered terbium, lanthanum and erbium.

Swedish chemist Carl Gustaf Mosander discovered terbium in 1843. He detected it as an impurity in yttrium oxide, Y2O3. Yttrium is named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques.[32][33][34]: 701 [35][32][36][37]

Mosander first separated yttria into three fractions, all named for the ore: yttria, erbia, and terbia. "Terbia" was originally the fraction that contained the pink color, due to the element now known as erbium. "Erbia" (containing what is now known as terbium) originally was the fraction that was essentially colorless in solution. The insoluble oxide of this element was noted to be tinged brown.

Later workers had difficulty in observing the minor colorless "erbia", but the soluble pink fraction was impossible to miss. Arguments went back and forth as to whether erbia even existed. In the confusion, the original names got reversed, and the exchange of names stuck, so that the pink fraction referred eventually to the solution containing erbium (which in solution, is pink). It is now thought that workers using double sodium or potassium sulfates to remove ceria from yttria inadvertently lost the terbium into the ceria-containing precipitate. What is now known as terbium was only about 1% of the original yttria, but that was sufficient to impart a yellowish color to the yttrium oxide. Thus, terbium was a minor component in the original fraction containing it, where it was dominated by its immediate neighbors, gadolinium and dysprosium.

Thereafter, whenever other rare earths were teased apart from this mixture, whichever fraction gave the brown oxide retained the terbium name, until at last, the brown oxide of terbium was obtained in pure form. The 19th century investigators did not have the benefit of the UV fluorescence technology to observe the brilliant yellow or green Tb(III) fluorescence that would have made terbium easier to identify in solid mixtures or solutions.[33]

Occurrence

Xenotime

Terbium is contained along with other rare earth elements in many minerals, including monazite ((Ce,La,Th,Nd,Y)PO4 with up to 0.03% terbium), xenotime (YPO4) and euxenite ((Y,Ca,Er,La,Ce,U,Th)(Nb,Ta,Ti)2O6 with 1% or more terbium). The crust abundance of terbium is estimated as 1.2 mg/kg.[23] No terbium-dominant mineral has yet been found.[38]

Currently, the richest commercial sources of terbium are the ion-adsorption

southern China; the concentrates with about two-thirds yttrium oxide by weight have about 1% terbia. Small amounts of terbium occur in bastnäsite and monazite; when these are processed by solvent extraction to recover the valuable heavy lanthanides as samarium-europium-gadolinium concentrate, terbium is recovered therein. Due to the large volumes of bastnäsite processed relative to the ion-adsorption clays, a significant proportion of the world's terbium supply comes from bastnäsite.[8]

In 2018, a rich terbium supply was discovered off the coast of

Minamitori Island, with the stated supply being "enough to meet the global demand for 420 years".[39]

Production

Crushed terbium-containing minerals are treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with caustic soda to pH 3–4. Thorium precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are decomposed to oxides by heating. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3. Terbium is separated as a double salt with ammonium nitrate by crystallization.[23]

The most efficient separation routine for terbium salt from the rare-earth salt solution is ion exchange. In this process, rare-earth ions are sorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. The rare earth ions are then selectively washed out by suitable complexing agents. As with other rare earths, terbium metal is produced by reducing the anhydrous chloride or fluoride with calcium metal. Calcium and tantalum impurities can be removed by vacuum remelting, distillation, amalgam formation or zone melting.[23]

Applications

Terbium is used as a

ZrO2.[8]

Terbium is also used in alloys and in the production of electronic devices. As a component of Terfenol-D, terbium is used in actuators, in naval sonar systems, sensors, in the SoundBug device (its first commercial application), and other magnetomechanical devices. Terfenol-D is a terbium alloy that expands or contracts in the presence of a magnetic field. It has the highest magnetostriction of any alloy.[40]

Terbium

incandescent lighting.[8]

Terbium is also used to detect

endospores, as it acts as an assay of dipicolinic acid based on photoluminescence.[41]

In 2023, terbium compounds were used to create a lattice with one iron (Fe) atom, that was then examined by synchrotron x-ray beam, to examine one atom at sub-atomic levels for the first time.[42]

Precautions

Handling of terbium, like other lanthanides, should be done with care. Terbium compounds show moderate toxicity, although there is limited data on the specific toxicity of the element. They can act as irritants to the skin and eyes upon contact. Ingestion of terbium compounds should be avoided due to their mildly toxic nature.[43][44]

In the event of exposure:

  • If inhaled: Move the person to fresh air, provide artificial respiration if breathing has stopped, and seek medical advice.
  • In case of skin contact: Wash immediately with soap and water, then rinse thoroughly and seek medical advice.
  • In case of eye contact: Rinse the eyes for several minutes under running water and consult a physician.
  • If swallowed: Seek immediate medical treatment.[45]

For safe handling and storage:

  • Keep terbium compounds in tightly sealed containers stored in a cool, dry place away from oxidizing agents.
  • Use personal protective equipment, such as impervious gloves and safety glasses, to prevent skin and eye contact.
  • Ensure adequate ventilation in the working area and avoid releasing terbium compounds into the environment without proper permits.[46]

Proper disposal of terbium compounds should be conducted in accordance with local environmental regulations.[47]

See also

References

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  9. ^ "Rare-Earth Metal Long Term Air Exposure Test". Retrieved 2009-05-05.
  10. ^ V.B. Taxak, R. Kumar, J.K. Makrandi, S.P. Khatkar Displays, 30 (2009), pp. 170–174
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  12. ^ Jackson, M. (2000). "Magnetism of Rare Earth" (PDF). The IRM Quarterly. 10 (3): 1.
  13. ^ a b "Chemical reactions of Terbium". Webelements. Retrieved 2009-06-06.
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  37. ^ Marshall, James L. Marshall; Marshall, Virginia R. Marshall (2015). "Rediscovery of the elements: The Rare Earths–The Confusing Years" (PDF). The Hexagon: 72–77. Retrieved 30 December 2019.
  38. ^ Hudson Institute of Mineralogy (1993–2018). "Mindat.org". www.mindat.org. Retrieved 14 January 2018.
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  43. ^ "Harmful Effects of Terbium". Vedantu. Retrieved 2023-11-07.
  44. ^ "Terbium". Los Alamos National Laboratory. Retrieved 2023-11-07.
  45. ^ "Terbium(III,IV) Oxide Safety Data Sheet". American Elements. Retrieved 2023-11-07.
  46. ^ Cite error: The named reference americanelementsstorage was invoked but never defined (see the help page).
  47. ^ "Terbium(III) oxide - Handling and Storage". Sciencemadness Wiki. Retrieved 2023-11-07.

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