Editing Terbium (section)

== Characteristics ==

=== Physical properties ===
Terbium is a silvery-white [[rare earth element|rare earth]] [[metal]] that is [[malleable]], [[ductile]] and soft enough to be cut with a knife.<ref name="CRC" /> It is relatively stable in air compared to the more reactive lanthanides in the first half of the lanthanide series.<ref>{{cite web| url = http://www.elementsales.com/re_exp/index.htm |title = Rare-Earth Metal Long Term Air Exposure Test| access-date = 2009-05-05}}</ref> Terbium exists in two crystal [[allotropy|allotropes]] with a transformation temperature of 1289&nbsp;°C between them.<ref name="CRC" /> The 65 electrons of a terbium atom are arranged in the [[electron configuration]] [Xe]4f<sup>9</sup>6s<sup>2</sup>. The eleven 4f and 6s electrons are [[valence electron|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]4f<sup>7</sup> configuration allows further ionization of a fourth electron in the presence of very strong oxidizing agents such as [[fluorine]] gas.<ref name="CRC" />

The terbium(III) cation (Tb<sup>3+</sup>) is brilliantly [[Fluorescence|fluorescent]], in a bright lemon-yellow color that is the result of a strong green [[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 [[europium]] (Eu<sup>3+</sup>) and Tb<sup>3+</sup> ions are among the lanthanide ions that have garnered the most attention because of their strong luminosity and great color purity.<ref>V.B. Taxak, R. Kumar, J.K. Makrandi, S.P. Khatkar Displays, 30 (2009), pp. 170–174</ref><ref>{{cite journal|last1=Shimada|first1=T.|last2=Ohno|first2=Y.|last3=Okazaki|first3=T.|last4=Sugai|first4=T.|last5=Suenaga|first5=K.|last6=Kishimoto|first6=S.|last7=Mizutani|first7=T.|last8=Inoue|first8=T.|last9=Taniguchi|first9=R.|last10=Fukui|display-authors=3 | first10=N.|last11=Okubo | first11=H.|last12=Shinohara | first12=H.|title=Transport properties of C<sub>78</sub>, C<sub>90</sub> and Dy@C<sub>82</sub> fullerenes – nanopeapods by field effect transistors|journal=Physica E: Low-dimensional Systems and Nanostructures|year=2004|volume=21|issue=2–4|pages=1089–1092|doi=10.1016/j.physe.2003.11.197|bibcode = 2004PhyE...21.1089S}}</ref>

Terbium has a simple [[ferromagnetic]] ordering at temperatures below 219&nbsp;K. Above 219&nbsp;K, it turns into a [[Helimagnetism|helical antiferromagnetic]] state in which all of the atomic moments in a particular [[basal plane]] layer are parallel and oriented at a fixed angle to the moments of adjacent layers. This antiferromagnetism transforms into a disordered [[paramagnetic]] state at 230&nbsp;K.<ref>{{cite journal| author =Jackson, M. | title =Magnetism of Rare Earth| url =http://www.irm.umn.edu/quarterly/irmq10-3.pdf | journal = The IRM Quarterly | volume =10| issue = 3| page = 1| date = 2000}}</ref>

=== 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 water.<ref name="reactions" />
:{{chem2|2 Tb (s) + 3 H2SO4 → 2 Tb(3+) + 3 SO4(2-) + 3 H2↑}}
:{{chem2|1=2 Tb + 3 X2 → 2 TbX3 (X = [[fluorine|F]], [[chlorine|Cl]], [[bromine|Br]], [[iodine|I]])}}
:{{chem2|2 Tb (s) + 6 H2O → 2 Tb(OH)3 + 3 H2↑}}
Terbium oxidizes readily in air to form a mixed [[terbium(III,IV) oxide]]:<ref name="reactions">{{cite web| url =https://www.webelements.com/terbium/chemistry.html| title =Chemical reactions of Terbium| publisher=Webelements| access-date=2009-06-06}}</ref>
:{{chem2|8 Tb + 7 O2 → 2 Tb4O7}}

The most common oxidation state of terbium is +3 (trivalent), such as in [[Terbium trichloride|{{chem|Tb||Cl|3}}]]. In the solid state, tetravalent terbium is also known, in compounds such as terbium oxide ({{chem2|TbO2}}) and terbium tetrafluoride.<ref>{{cite journal|title=Higher Oxides of the Lanthanide Elements: Terbium Dioxide|author=Gruen, D. M. |author2=Koehler, W. C. |author3=Katz, J. J. |date=April 1951|pages=1475–1479|volume=73|journal=Journal of the American Chemical Society|doi=10.1021/ja01148a020|issue=4|bibcode=1951JAChS..73.1475G }}</ref> In solution, terbium typically forms trivalent species, but can be oxidized to the tetravalent state with [[ozone]] in highly basic aqueous conditions.<ref>{{cite journal |title=Stabilization of Praseodymium(IV) and Terbium(IV) in Aqueous Carbonate Solution |author1=Hobart, D. E. |author2= Samhoun, K. |author3= Young, J. P. |author4=Norvell, V. E. |author5= Mamantov, G. |author6= Peterson, J. R. |date=1980 |pages=321–328 |volume=16 |journal=Inorganic and Nuclear Chemistry Letters |doi=10.1016/0020-1650(80)80069-9 |issue=5}}</ref>

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]].<ref>{{Cite journal |last1=Zhuang |first1=Jia-Jia |last2=Chen |first2=Ming-Guang |last3=Sun |first3=Yan-Bing |last4=Hang |first4=Pei |last5=Sui |first5=Yang |last6=Tong |first6=Jia-Ping |date=2020-03-01 |title=Synthesis, Structure and Magnetic Property of a Tricapped Trigonal Prismatic Tb<sup>III</sup>-Based 3d-4f Complex |journal=IOP Conference Series: Materials Science and Engineering |volume=774 |issue=1 |pages=012042 |doi=10.1088/1757-899X/774/1/012042 |issn=1757-8981|doi-access=free |bibcode=2020MS&E..774a2042Z }}</ref> Complexes of terbium with lower coordination number are also known, typically with bulky ligands like [[Metal bis(trimethylsilyl)amides|bis(trimethylsilyl)amide]], which forms the three-coordinate tris[N,N-bis(trimethylsilyl)amide]terbium(III) ({{chem2|Tb[N(SiMe3)2]3}}) complex.<ref>{{Cite journal |last1=Boyde |first1=Nicholas C. |last2=Chmely |first2=Stephen C. |last3=Hanusa |first3=Timothy P. |last4=Rheingold |first4=Arnold L. |last5=Brennessel |first5=William W. |date=2014-09-15 |title=Structural Distortions in M[E(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> Complexes (M = Group 15, f-Element; E = N, CH): Is Three a Crowd? |url=https://pubs.acs.org/doi/10.1021/ic501232z |journal=Inorganic Chemistry |language=en |volume=53 |issue=18 |pages=9703–9714 |doi=10.1021/ic501232z |pmid=25171144 |issn=0020-1669}}</ref>

Most coordination and organometallic complexes contain terbium in the trivalent oxidation state. Divalent Tb<sup>2+</sup> complexes are also known, usually with bulky [[Cyclopentadienyl complex|cyclopentadienyl-type ligands]].<ref>{{cite journal |title=Tetramethylcyclopentadienyl Ligands Allow Isolation of Ln(II) Ions across the Lanthanide Series in [K(2.2.2-cryptand)][(C<sub>5</sub>Me<sub>4</sub>H)<sub>3</sub>Ln] Complexes |author1=Jenkins, T. F. |author2= Woen, D. H |author3= Mohanam, L. N. |author4=Ziller, J. W. |author5=Furche, F. |author6=Evans, W. J. |date=2018|pages=3863–3873|volume=141 |journal=Organometallics |doi=10.1021/acs.organomet.8b00557 |issue=21|s2cid=105379627 }}</ref><ref>{{cite journal |title=Completing the Series of +2 Ions for the Lanthanide Elements: Synthesis of Molecular Complexes of Pr<sup>2+</sup>, Gd<sup>2+</sup>, Tb<sup>2+</sup>, and Lu<sup>2+</sup> |author1=Macdonald, M. R. |author2= Bates, J. E. |author3= Ziller, J. W. |author4=Furche, F. |author5=Evans, W. J. |date=2013|pages=9857–9868|volume=135|journal=Journal of the American Chemical Society|doi=10.1021/ja403753j|issue=21|pmid=23697603 |bibcode=2013JAChS.135.9857M }}</ref><ref>{{Cite journal|last1=Gould|first1=C. A.|last2=McClain|first2=K. R. |last3=Yu|first3=J. M.|last4=Groshens|first4=T. J.|last5=Furche|first5=F. P.|last6=Harvey|first6=B. G.|last7=Long|first7=J. R.|date=2019-08-21|title=Synthesis and Magnetism of Neutral, Linear Metallocene Complexes of Terbium(II) and Dysprosium(II)|journal=Journal of the American Chemical Society|volume=141|issue=33|pages=12967–12973|doi=10.1021/jacs.9b05816|pmid=31375028|bibcode=2019JAChS.14112967G |s2cid=199388151|issn=0002-7863}}</ref> A few coordination compounds containing terbium in its tetravalent state are also known.<ref>{{cite journal |title=Molecular Complex of Tb in the +4 Oxidation State |author1=Palumbo, C. T. |author2=Zivkovic, I. |author3=Scopelliti, R. |author4=Mazzanti, M. |date=2019 |pages=9827–9831 |volume=141 |journal=Journal of the American Chemical Society |doi=10.1021/jacs.9b05337 |pmid=31194529 |issue=25 |bibcode=2019JAChS.141.9827P |s2cid=189814301 |url=http://infoscience.epfl.ch/record/268286/files/Palumbo%20ja-2019-05337d%20manuscriptR1.pdf |archive-url=https://web.archive.org/web/20240423040613/https://infoscience.epfl.ch/record/268286/files/Palumbo%20ja-2019-05337d%20manuscriptR1.pdf |url-status=dead |archive-date=April 23, 2024 }}</ref><ref>{{Cite journal|last1=Rice|first1=N. T.|last2=Popov|first2=I. A.|last3=Russo|first3=D. R.|last4=Bacsa|first4=J.|last5=Batista|first5=E. R.|last6=Yang|first6=P.|last7=Telser|first7=J.|last8=La Pierre|first8=H. S.|date=2019-08-21|title=Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex|journal=Journal of the American Chemical Society|volume=141|issue=33|pages=13222–13233|doi=10.1021/jacs.9b06622|pmid=31352780|bibcode=2019JAChS.14113222R |osti=1558225|s2cid=207197096|issn=0002-7863|url=https://figshare.com/articles/journal_contribution/9450461 }}</ref><ref>{{cite journal |title= Stabilization of the Oxidation State +IV in Siloxide-Supported Terbium Compounds |author1=Willauer, A. R. |author2=Palumbo, C. T. |author3=Scopelliti, R. |author4=Zivkovic, I. |author5=Douair, I. |author6=Maron, L.  |author7=Mazzanti, M. |date=2020 |pages=3549–3553|volume=59 |journal=Angewandte Chemie International Edition |issue=9 |doi=10.1002/anie.201914733|pmid=31840371 |s2cid=209385870 |url=https://infoscience.epfl.ch/record/275738/files/Mazzanti_et_al-2019-Angewandte_Chemie_International_Edition-2.pdf }}</ref>

==== Oxidation states ====
Like most [[rare-earth elements]] and [[lanthanides]], terbium is usually found in the +3 oxidation state. Like [[cerium]] and [[praseodymium]], terbium can also form a +4 oxidation state,<ref name=":1">{{Cite journal |last1=Palumbo |first1=Chad T. |last2=Zivkovic |first2=Ivica |last3=Scopelliti |first3=Rosario |last4=Mazzanti |first4=Marinella |date=2019-06-26 |title=Molecular Complex of Tb in the +4 Oxidation State |url=https://pubs.acs.org/doi/10.1021/jacs.9b05337 |journal=Journal of the American Chemical Society |language=en |volume=141 |issue=25 |pages=9827–9831 |doi=10.1021/jacs.9b05337 |pmid=31194529 |bibcode=2019JAChS.141.9827P |issn=0002-7863}}</ref> although it is unstable in water.<ref>{{Greenwood&Earnshaw2nd}}</ref> It is possible for terbium to be found in the 0,<ref name="Cloke">{{cite journal |last=Cloke |first=F. Geoffrey N. |date=1993 |title=Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides |journal=Chem. Soc. Rev. |volume=22 |pages=17–24 |doi=10.1039/CS9932200017}}</ref><ref name="Arnold">{{cite journal |last1=Arnold |first1=Polly L. |last2=Petrukhina |first2=Marina A. |last3=Bochenkov |first3=Vladimir E. |last4=Shabatina |first4=Tatyana I. |last5=Zagorskii |first5=Vyacheslav V. |last6=Cloke |first9=F. Geoffrey N. |date=2003-12-15 |title=Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation |journal=Journal of Organometallic Chemistry |volume=688 |issue=1–2 |pages=49–55 |doi=10.1016/j.jorganchem.2003.08.028}}</ref> +1,<ref name="Wan-Lu Li">{{cite journal |last1=Li |first1=Wan-Lu |last2=Chen |first2=Teng-Teng |last3=Chen |first3=Wei-Jia |last4=Li |first4=Jun |last5=Wang |first5=Lai-Sheng |year=2021 |title=Monovalent lanthanide(I) in borozene complexes |journal=Nature Communications |volume=12 |issue=1 |page=6467 |bibcode=2021NatCo..12.6467L |doi=10.1038/s41467-021-26785-9 |pmc=8578558 |pmid=34753931}}</ref> and +2<ref name=":1" /> oxidation states.

=== Compounds ===
{{Main article|Terbium compounds}}
{{multiple image | direction = vertical | width = 200
|align=right
|image1=Tb-sulfate.jpg
|image2=Tb-sulfate-luminescence.jpg
|caption2=Terbium sulfate, {{chem2|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 {{chem2|TbH2}}, {{chem2|TbH3}}, {{chem2|TbB2}}, {{chem2|Tb2S3}}, {{chem2|TbSe}}, {{chem2|TbTe}} and {{chem2|[[terbium(III) nitride|TbN]]}}.<ref name="patnaik" /> In these compounds, terbium mainly exhibits the oxidation state +3, with the +2 state appearing rarely. Terbium(II) halides are obtained by [[annealing (materials science)|annealing]] terbium(III) halides in presence of metallic terbium in [[tantalum]] containers. Terbium also forms the sesquichloride {{chem2|Tb2Cl3}}, which can be further reduced to terbium(I) chloride ({{Chem2|TbCl}}) by annealing at 800&nbsp;°C; this compound forms platelets with layered graphite-like structure.<ref>{{cite book| page=1128| url=https://books.google.com/books?id=U3MWRONWAmMC&pg=PA1128| title =Advanced inorganic chemistry| edition =6th| author= Cotton| publisher= Wiley-India| date = 2007| isbn =978-81-265-1338-3}}</ref>

[[Terbium(IV) fluoride]] ({{Chem2|TbF4}}) is the only halide that tetravalent terbium can form. It has strong oxidizing properties and is a strong [[halogenation|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]].<ref>{{cite journal |last1=Rau |first1=J. V. |last2=Chilingarov |first2=N. S. |last3=Leskiv |first3=M. S. |last4=Sukhoverkhov |first4=V. F. |last5=Rossi Albertini |first5=V. |last6=Sidorov |first6=L. N. |title=Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine |journal=Le Journal de Physique IV |date=August 2001 |volume=11 |issue=PR3 |pages=Pr3–109–Pr3-113 |doi=10.1051/jp4:2001314}}</ref> It can be obtained by reacting [[terbium(III) chloride]] or [[terbium(III) fluoride]] with [[fluorine]] gas at 320&nbsp;°C:<ref>{{Cite book|author=G. Meyer |author2=Lester R. Morss |title= Synthesis of Lanthanide and Actinide Compounds |publisher=Springer Science & Business Media|year= 1991|page=60|isbn= 978-0-7923-1018-1 |url = https://books.google.com/books?id=bnS5elHL2w8C&pg=PA60}}</ref>
: 2 TbF<sub>3</sub> + F<sub>2</sub> → 2 TbF<sub>4</sub>
When {{Chem2|TbF4}} and [[caesium fluoride]] (CsF) is mixed in a stoichiometric ratio in a fluorine gas atmosphere, caesium pentafluoroterbate ({{Chem2|CsTbF5}}) is obtained. It is an [[orthorhombic crystal system|orthorhombic]] crystal with [[space group]] ''Cmca'' and a layered structure composed of [TbF<sub>8</sub>]<sup>4−</sup> and 11-coordinated Cs<sup>+</sup>.<ref>{{cite journal|last1=Gaumet|first1=V.|last2=Avignant|first2=D.|title=Caesium Pentafluoroterbate, CsTbF<sub>5</sub>|journal=Acta Crystallographica Section C: Crystal Structure Communications|volume=53|issue=9|year=1997|pages=1176–1178 |doi=10.1107/S0108270197005556|bibcode=1997AcCrC..53.1176G }}</ref> The compound barium hexafluoroterbate ({{Chem2|BaTbF6}}), an orthorhombic crystal with space group ''Cmma'', can be prepared in a similar method. The terbium fluoride ion [TbF<sub>8</sub>]<sup>4−</sup><ref>{{cite journal|last1=Largeau|first1=E.|last2=El-Ghozzi|first2=M.|last3=Métin|first3=J.|last4=Avignant|first4=D.|title=β-BaTbF6|journal=Acta Crystallographica Section C: Crystal Structure Communications|volume=53|issue=5|year=1997|pages=530–532 |doi=10.1107/S0108270196014527|bibcode=1997AcCrC..53..530L }}</ref> also exists in the structure of potassium terbium fluoride crystals.<ref>{{Cite journal |last1=Balodhi |first1=Ashiwini |last2=Chang |first2=Kelvin |last3=Stevens |first3=Kevin T. |last4=Chakrapani |first4=Sunil K. |last5=Ennaceur |first5=Susan M. |last6=Migliori |first6=Albert |last7=Zevalkink |first7=Alexandra |date=2020-10-26 |title=Determination of single crystal elastic moduli of KTb<sub>3</sub>F<sub>10</sub> by resonant ultrasound spectroscopy |url=https://pubs.aip.org/aip/jap/article/128/16/165104/568450/Determination-of-single-crystal-elastic-moduli-of |journal=Journal of Applied Physics |volume=128 |issue=16 |doi=10.1063/5.0024723 |bibcode=2020JAP...128p5104B |issn=0021-8979}}</ref><ref>{{Cite journal |last1=Valiev |first1=Uygun V. |last2=Karimov |first2=Denis N. |last3=Ma |first3=Chong-Geng |last4=Sultonov |first4=Odiljon Z. |last5=Pelenovich |first5=Vasiliy O. |date=2022-11-12 |title=Tb<sup>3+</sup> Ion Optical and Magneto-Optical Properties in the Cubic Crystals KTb<sub>3</sub>F<sub>10</sub> |journal=Materials |language=en |volume=15 |issue=22 |pages=7999 |doi=10.3390/ma15227999 |issn=1996-1944 |pmc=9693278 |pmid=36431487 |doi-access=free|bibcode=2022Mate...15.7999V }}</ref>

[[Terbium(III) oxide]] or terbia is the main oxide of terbium, and appears as a dark brown water-insoluble solid. It is slightly hygroscopic<ref name=":02">{{Cite book |last1=Larrañaga |first1=Michael D. |url=https://onlinelibrary.wiley.com/doi/book/10.1002/9781119312468 |title=Hawley's Condensed Chemical Dictionary |last2=Lewis |first2=Richard J. |last3=Lewis |first3=Robert A. |date=September 2016 |publisher=Wiley |isbn=978-1-118-13515-0 |edition=16th |pages=1310 |language=en |doi=10.1002/9781119312468}}</ref> and is the main terbium compound found in rare earth-containing minerals and clays.<ref name=":2" />

Other compounds include: 
* [[Chloride]]s: {{chem2|[[terbium(III) chloride|TbCl3]]}}
* [[Bromide]]s: {{chem2|[[terbium(III) bromide|TbBr3]]}}
* [[Iodide]]s: {{chem2|[[terbium(III) iodide|TbI3]]}}
* [[Fluoride]]s: {{chem2|[[terbium(III) fluoride|TbF3]]}}, {{chem2|[[terbium(IV) fluoride|TbF4]]}}

=== Isotopes ===
{{Main|Isotopes of terbium}}
Naturally occurring terbium is composed of its only stable [[isotope]], terbium-159; the element is thus [[mononuclidic element|mononuclidic]] and [[monoisotopic element|monoisotopic]].<ref name="CIAAWterbium"/> Thirty-nine [[radioisotope]]s have been characterized,{{AME2020 II|ref}} with the heaviest being terbium-174 and lightest being terbium-135 (both with unknown exact mass).{{NUBASE2020|ref}} The most stable [[synthetic radioisotope]]s of terbium are terbium-158, with a [[half-life]] of 180 years, and terbium-157, with a half-life of 71 years. All of the remaining [[radioactive]] isotopes have half-lives that are less than three months, and the majority of these have half-lives that are less than half a minute.{{NUBASE2020|ref}} The primary [[decay mode]] before the most abundant stable isotope, {{sup|159}}Tb, is [[electron capture]], which results in production of [[gadolinium]] isotopes, and the primary mode after is [[beta minus decay]], resulting in [[dysprosium]] isotopes.{{NUBASE2020|ref}}

The element also has 31 [[nuclear isomer]]s, with masses of 141–154, 156, 158, 162, and 164–168 (not every mass number corresponds to only one isomer).{{AME2020 II|ref}} 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.{{NUBASE2020|ref}}

Terbium-149, with a half-life of 4.1 hours, is a promising candidate in [[targeted alpha therapy]] and [[positron emission tomography]].<ref>{{cite journal | last1=Müller | first1=Cristina | last2=Vermeulen | first2=Christiaan | last3=Köster | first3=Ulli | last4=Johnston | first4=Karl | last5=Türler | first5=Andreas | last6=Schibli | first6=Roger | last7=van der Meulen | first7=Nicholas P. | title=Alpha-PET with terbium-149: evidence and perspectives for radiotheragnostics | journal=EJNMMI Radiopharmacy and Chemistry | publisher=Springer Science and Business Media LLC | volume=1 | issue=1 | date=2016-03-28 | page=5 | issn=2365-421X | doi=10.1186/s41181-016-0008-2| pmid=29564382 | pmc=5843804 | doi-access=free }}</ref><ref>{{cite journal | last1=Eychenne | first1=Romain | last2=Chérel | first2=Michel | last3=Haddad | first3=Férid | last4=Guérard | first4=François | last5=Gestin | first5=Jean-François | title=Overview of the Most Promising Radionuclides for Targeted Alpha Therapy: The "Hopeful Eight" | journal=Pharmaceutics | publisher=MDPI AG | volume=13 | issue=6 | date=2021-06-18 | issn=1999-4923 | doi=10.3390/pharmaceutics13060906 | page=906 | pmid=34207408 | pmc=8234975 | doi-access=free }}</ref>