Terbium (Tb)
lanthanideSolid
Standard Atomic Weight
158.92535 uElectron configuration
[Xe] 6s2 4f9Melting point
1355.85 °CBoiling point
3229.85 °CDensity
8230 kg/m³Oxidation states
0, +1, +2, +3, +4Electronegativity (Pauling)
N/AIonization energy (1st)
5.8638 eVDiscovery year
1843Atomic radius
175 pmDetails
Terbium is a lanthanide rare-earth metal with atomic number 65. It is chemically similar to neighboring gadolinium and dysprosium and occurs in minerals with other rare earths rather than as a native element. Its most distinctive technological role comes from Tb³⁺ luminescence, which gives intense green emission in suitable host materials, and from the large magnetostrictive response of terbium-containing alloys.
Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289°C. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color.
The name derives from the village of Ytterby in Sweden, where the mineral ytterbite (the source of terbium) was first found. Terbium was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1843 in an yttrium salt, which he resolved into three elements. He called one yttrium, a rose-colored salt he called terbium, and a deep-yellow peroxide he called erbium. In 1862, the Swiss chemist Marc Delafontaine reexamined yttrium and found the yellow peroxide. Because the name erbium had now been assigned to the rose-colored oxide, he reintroduced the name terbium for the yellow peroxide. Thus the original names given to erbium and terbium samples are now switched.
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. From these two substances, Mosander discovered two new elements, terbium and erbium. Today, terbium can be obtained from the minerals xenotime (YPO4) and euxenite ((Y, Ca, Er, La, Ce, U, Th)(Nb, Ta, Ti)2O6), but is primarily obtained through an ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO4), a material rich in rare earth elements that typically contains as much as 0.03% terbium.
Discovered by Mosander in 1843. Terbium is a member of the lanthanide or "rare earth" group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earths. It is recovered commercially from monazite in which it is present to the extent of 0.03%, from xenotime, and from euxenite, a complex oxide containing 1% or more of terbia.
Pure terbium is a soft, silvery-gray metal. It is malleable enough to be cut and, like many lanthanides, slowly tarnishes in air as surface oxides form. It has more than one solid allotrope, with a structural change at elevated temperature.
Terbium is used mainly in small amounts where its optical or magnetic properties are valuable. Tb³⁺ activators provide green emission in phosphors for lighting, displays, and some X-ray imaging materials. Terbium is also a component of Terfenol-D, a terbium-dysprosium-iron magnetostrictive alloy used in actuators, sonar transducers, and vibration-control devices. In research and specialized instruments, terbium compounds are used as luminescent probes and magnetic materials.
Terbium is used to dope some types of solid-state devices and, along with zirconium dioxide (ZrO2), as a crystal stabilizer in fuel cells that operate at high temperatures.
Terbia, the renamed material that Mosander discovered in 1843, is terbium oxide (Tb2O3), one of terbium's compounds. Terbia can potentially be used as an activator for green phosphors in television tubes. Sodium terbium borate, another terbium compound, is used to make laser light.
Sodium terbium borate is used in solid-state devices. It can be used with ZrO2 as a crystal stabilizer of fuel cells which operate at elevated temperature. Few other uses have been found.
Isotopes in Medicine
149Tb (with a half-life of 4.1 h) is being used in targeted radiotherapy using alpha particles for labeling radioimmunoconjugates in cancer treatments [458] N. G. Zaitseva, S. N. Dmitriev, O. D. Maslov, L. G. Molokanova, G. Y. Starodub, S. V. Shishkin, T. V. Shishkina, G. J. Beyer. Czech. J. Phys. Suppl.53, A455 (2003)., [459] G. J. Beyer, M. Miederer, S. Vranjes-Duric, J. J. Comor, G. Kunzi, O. Hartley, R. Senekowitsch-Schmidtke, D. Soloviev, F. Buchegger. Eur. J. Nucl. Med. Mol. Imaging31, 547 (2004).. 161Tb (with a half-life of 6.9 days) attached to a bioconjugate (two covalently linked molecules, one or more of which is a biomolecule), is being used in cancer therapy as a targeted radiation treatment of cancer cells [459] G. J. Beyer, M. Miederer, S. Vranjes-Duric, J. J. Comor, G. Kunzi, O. Hartley, R. Senekowitsch-Schmidtke, D. Soloviev, F. Buchegger. Eur. J. Nucl. Med. Mol. Imaging31, 547 (2004)., [460] S. Lehenberger, C. Barkhausen, S. Cohrs, E. Fischer, J. Grünberg, A. Hohn, U. Köster, R. Schibli, A. Türler, K. Zhernosekov. Nucl. Med. Biol.38, 917 (2011).. 161Tb is being used for imaging as it allows for on-line monitoring of its distribution using gamma cameras [460] S. Lehenberger, C. Barkhausen, S. Cohrs, E. Fischer, J. Grünberg, A. Hohn, U. Köster, R. Schibli, A. Türler, K. Zhernosekov. Nucl. Med. Biol.38, 917 (2011).. 149Tb is produced by the reaction 142Nd(12C,5n) 149Dy, which is followed by a subsequent positron decay reaction 149Dy→ 149Tb+β +. It can also be produced by the reaction 141Pr(12C,4n) 149Tb; beam geometry is important for satisfactory yield of 149Tb (Fig. IUPAC.65.1) [461] S. Sarkar, B. J. Allen, S. Imam, G. Goozee, J. Leigh, H. Meriaty. “Production and separation of terbium-149,152 for targeted cancer therapy”, in Second international conference on isotopes; Sydney, NSW (Australia); 273 p. Conference proceedings, 12–16 Oct 1997, C. J. Hardy (Ed.), Australian Nuclear Association Inc., Sutherland, NSW (Australia), pp. 206–211..
Terbium most commonly forms trivalent compounds containing Tb³⁺. Representative materials include terbium(III) oxide, Tb₂O₃, terbium(III) chloride, TbCl₃, and terbium(III) fluoride, TbF₃. Unlike many lanthanides, terbium also has accessible tetravalent chemistry in strongly oxidizing oxide and fluoride environments; terbium(IV) oxide, TbO₂, is a well established example. Mixed-valence oxides and doped host lattices are important because they tune luminescence, oxygen storage, and magnetic behavior.
See more information at the Terbium compound page.
Metallic terbium is not highly toxic in ordinary handling, but powders can be a fire and dust hazard, and soluble terbium salts should be treated as harmful laboratory chemicals. Fine metal reacts more readily with air and moisture than bulk pieces. Terbium has no known biological role. Commercial terbium is essentially stable isotopically; radiological hazards apply only to artificially produced radioactive isotopes or activated materials.
Little is known of the toxicity of terbium. It should be handled with care as with other lanthanide element
Terbium is a dispersed lithophile element found in rare-earth minerals such as monazite, bastnäsite, xenotime, and ion-adsorption clays. In soils and waters it is generally immobile because Tb³⁺ binds strongly to phosphates, carbonates, oxides, and organic matter. Natural concentrations are low, and biological uptake is limited. Environmental concern is usually associated with mining, acid leaching, and waste handling rather than with terbium metal itself.
Terbium is produced as a separated rare-earth product, not mined alone. Ores and concentrates are processed to dissolve mixed rare earths, then solvent extraction or ion exchange separates terbium from chemically similar lanthanides. Supply is constrained by the low abundance of terbium in many deposits, the complexity of separation, and dependence on rare-earth refining capacity. Demand is driven by phosphors and magnetostrictive alloys, but use per device is usually small. Recycling is technically possible from phosphor powders and some magnets or alloys, yet collection and separation are often limiting.
Found with other rare earths in monazite sand, which typically contain 0.03% terbium. Other sources are xenotime and euxenite, both of which are oxide mixtures that can contain up to 1% terbium.
Terbium is a heavy rare-earth element made mainly by neutron-capture nucleosynthesis in earlier generations of stars, with contributions from slow and rapid neutron-capture processes. It is far less abundant cosmically than iron-group elements and lighter rock-forming elements. In planetary materials it follows other trivalent lanthanides and concentrates in refractory mineral phases rather than volatile reservoirs.
- Terbium has only one stable natural isotope, ¹⁵⁹Tb.
- Its name comes from Ytterby, the Swedish locality linked to several rare-earth element names.
- Tb³⁺ emission is commonly used as a green reference in luminescence spectroscopy.
- Terfenol-D takes its name from terbium, iron, Naval Ordnance Laboratory, and dysprosium.
- Terbium can form stable Tb⁴⁺ in oxides more readily than most lanthanides.
Images
Properties
Physical
- Atomic radius (empirical)
- 175 pm Compare Atomic radius (empirical) of all elements →
- Covalent radius
- 194 pm Compare Covalent radius of all elements →
- Van der Waals radius
- 221 pm Compare Van der Waals radius of all elements →
- Density
- 8230 kg/m³ Compare Density of all elements →
- Molar volume
- 0.0192 L/mol
- Phase at STP
- Solid Compare Phase at STP of all elements →
- Melting point
- 1355.85 °C Compare Melting point of all elements →
- Boiling point
- 3229.85 °C Compare Boiling point of all elements →
- Thermal conductivity
- 11.1 W/(m·K) Compare Thermal conductivity of all elements →
- Specific heat capacity
- 0.182 J/(g·K) Compare Specific heat capacity of all elements →
- Molar heat capacity
- 28.91 J/(mol·K) Compare Molar heat capacity of all elements →
- Crystal structure
- Hexagonal close-packed Compare Crystal structure of all elements →
Chemical
- Electron affinity
- 1.124 eV
- Ionization energy (1st)
- 5.8638 eV Compare Ionization energy (1st) of all elements →
- Ionization energy (2nd)
- 11.51304 eV Compare Ionization energy (2nd) of all elements →
- Ionization energy (3rd)
- 21.820075 eV Compare Ionization energy (3rd) of all elements →
- Ionization energy (4th)
- 39.330135 eV Compare Ionization energy (4th) of all elements →
- Ionization energy (5th)
- 66.500229 eV Compare Ionization energy (5th) of all elements →
- Oxidation states
- 0, +1, +2, +3, +4 Compare Oxidation states of all elements →
- Valence electrons
- 3 Compare Valence electrons of all elements →
- Electron configuration
- [Xe] 6s2 4f9
Thermodynamic
- Heat of fusion
- 0.1119345 eV Compare Heat of fusion of all elements →
- Heat of vaporization
- 3.016013 eV Compare Heat of vaporization of all elements →
- Heat of sublimation
- 4.031715 eV
- Heat of atomization
- 4.031715 eV
- Atomization enthalpy
- 4.028605 eV
Nuclear
- Protons
- 65 Compare Protons of all elements →
- Neutrons
- 94 Compare Neutrons of all elements →
- Known isotopes
- 40 Compare Known isotopes of all elements →
- Stable isotopes
- 1 Compare Stable isotopes of all elements →
- Most stable isotope
- Tb-159
- Discovery year
- 1843
Abundance
- Abundance (Earth's crust)
- 1.2 mg/kg Compare Abundance (Earth's crust) of all elements →
- Abundance (ocean)
- 1.4 × 10−7 mg/L Compare Abundance (ocean) of all elements →
Crystal Structure
- Lattice constant a
- 360 pm
Electronic Structure
- Electrons per shell
- 2, 8, 18, 27, 8, 2 Compare Electrons per shell of all elements →
Identifiers
- CAS number
- 7440-27-9 Compare CAS number of all elements →
- Term symbol
- 6H°15/2
- InChI
- InChI=1S/Tb
- InChI Key
- GZCRRIHWUXGPOV-UHFFFAOYSA-N
Electron Configuration Measured
Tb: 4f⁹ 6s²[Xe] 4f⁹ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f⁹ 6s²Atomic model
Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.
Schematic atomic model, not to scale.
Atomic Fingerprint
Emission / Absorption Spectrum
Isotope Distribution
| Mass number | Atomic mass (u) | Natural abundance | Half-life |
|---|---|---|---|
| 159 Stable | 158.9253547 ± 0.0000019 | 100.0000% | Stable |
Phase / State
Reason: 1330.8 °C below melting point (1355.85 °C)
Schematic, not to scale
Phase transition points
Transition energies
Energy required to melt 1 mol at melting point
Energy required to vaporize 1 mol at boiling point
Energy required to sublime 1 mol at sublimation point
Density
At standard conditions
At standard conditions
Atomic Spectra
Showing 10 of 65. Sorted by ion charge (ascending).
Lines Holdings ?
| Ion | Charge | Total lines | Transition probabilities | Level designations |
|---|---|---|---|---|
| Tb I | 0 | 248 | 0 | 10 |
| Tb II | +1 | 424 | 8 | 18 |
| Tb IV | +3 | 48 | 0 | 0 |
Levels Holdings ?
| Ion | Charge | Levels |
|---|---|---|
| Tb I | 0 | 600 |
| Tb II | +1 | 154 |
| Tb III | +2 | 125 |
| Tb IV | +3 | 26 |
| Tb V | +4 | 2 |
| Tb VI | +5 | 2 |
| Tb VII | +6 | 2 |
| Tb VIII | +7 | 2 |
| Tb IX | +8 | 2 |
| Tb X | +9 | 2 |
Ionic Radii
| Charge | Coordination | Spin | Radius |
|---|---|---|---|
| +3 | 6 | N/A | 92.30000000000001 pm |
| +3 | 7 | N/A | 98 pm |
| +3 | 8 | N/A | 104 pm |
| +3 | 9 | N/A | 109.5 pm |
| +4 | 6 | N/A | 76 pm |
| +4 | 8 | N/A | 88 pm |
Compounds
Isotopes (1)
| Mass number | Atomic mass (u) | Natural abundance | Half-life | Decay mode | |
|---|---|---|---|---|---|
| 159 Stable | 158.9253547 ± 0.0000019 | 100.0000% | Stable | stable |
Extended Properties
Covalent Radii (Extended)
- Covalent radius (Pyykkö)
- 168 pm
- Covalent radius (Pyykkö, double)
- 135 pm
Van der Waals Radii
- Alvarez
- 279 pm
- UFF
- 345.1 pm
- MM3
- 270 pm
Atomic & Metallic Radii
- Atomic radius (Rahm)
- 276 pm
Numbering Scales
- Mendeleev
- 29
- Pettifor
- 26
- Glawe
- 25
Electronegativity Scales
- Ghosh
- 0
- Miedema
- 3
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 3
Polarizability & Dispersion
- Dipole polarizability
- 170 a.u.
- Dipole polarizability (unc.)
- 20 a.u.
- C₆ (Gould–Bučko)
- 2590 Ha·Bohr6
Miedema Parameters
- Miedema molar volume
- 19.32 cm3/mol
- Miedema electron density
- 2
Supply Risk & Economics
- Production concentration
- 97
- Relative supply risk
- 10
- Reserve distribution
- 50
- Political stability (top producer)
- 24
- Political stability (top reserve)
- 24
Phase Transitions & Allotropes
| Melting point | 1632.15 K |
| Boiling point | 3503.15 K |
Oxidation State Categories
Advanced Reference Data
Screening Constants (13)
| n | Orbital | σ |
|---|---|---|
| 1 | s | 1.2739 |
| 2 | p | 4.3076 |
| 2 | s | 17.0278 |
| 3 | d | 13.7015 |
| 3 | p | 19.9853 |
| 3 | s | 20.4485 |
| 4 | d | 34.69 |
| 4 | f | 39.1352 |
| 4 | p | 31.6012 |
| 4 | s | 30.98 |
Crystal Radii Detail (6)
| Charge | CN | Spin | rcrystal (pm) | Origin |
|---|---|---|---|---|
| 3 | VI | 106.3 | from r^3 vs V plots, | |
| 3 | VII | 112 | estimated, | |
| 3 | VIII | 118 | from r^3 vs V plots, | |
| 3 | IX | 123.5 | from r^3 vs V plots, | |
| 4 | VI | 90 | from r^3 vs V plots, | |
| 4 | VIII | 102 |
Isotope Decay Modes (63)
| Isotope | Mode | Intensity |
|---|---|---|
| 135 | p | 100% |
| 135 | B+ | — |
| 136 | B+ | — |
| 136 | B+p | — |
| 137 | p | — |
| 137 | B+ | — |
| 138 | B+ | — |
| 138 | B+p | — |
| 138 | p | 0% |
| 139 | B+ | 100% |
X‑ray Scattering Factors (514)
| Energy (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 0.15974 |
| 10.1617 | — | 0.16625 |
| 10.3261 | — | 0.17301 |
| 10.4931 | — | 0.18005 |
| 10.6628 | — | 0.18738 |
| 10.8353 | — | 0.19501 |
| 11.0106 | — | 0.20295 |
| 11.1886 | — | 0.21121 |
| 11.3696 | — | 0.21981 |
| 11.5535 | — | 0.22823 |
Additional Data
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
1.2 milligrams per kilogram
References (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
1.4×10-7 milligrams per liter
References (1)
Production
Production of this element (from raw materials or other compounds containing the element).
Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. As with other rare earth metals, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible.
References (1)
- [6] Terbium https://periodic.lanl.gov/65.shtml
References
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Terbium.
The element property data was retrieved from publications.