Editing Thulium (section)

==Properties==

===Physical properties===
Pure thulium metal has a bright, silvery luster, which tarnishes on exposure to air. The metal can be cut with a knife,<ref name="history" /> as it has a [[Mohs hardness]] of 2 to 3; it is malleable and ductile.<ref name="CRC" /> Thulium is [[ferromagnetic]] below 32{{nbsp}}K, [[antiferromagnetic]] between 32 and 56{{nbsp}}K, and [[paramagnetic]] above 56{{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>

Thulium has two major [[allotrope]]s: the [[tetragonal crystal system|tetragonal]] α-Tm and the more stable [[hexagonal crystal system|hexagonal]] β-Tm.<ref name="CRC" />

===Chemical properties===
Thulium tarnishes slowly in air and burns readily at 150{{nbsp}}[[Celsius|°C]] to form [[thulium(III) oxide]]:<ref name="InorgChem">{{cite book
| title = Inorganic Chemistry, 3rd Edition
| chapter = Chapter 25: The ''f''-block metals: lanthanoids and actinoids
| author1 = Catherine E. Housecroft
| author2 = Alan G. Sharpe
| publisher = Pearson
| year = 2008
| isbn = 978-0-13-175553-6
| page = 864
}}</ref>
:{{chem2|4Tm + 3O2 → 2Tm2O3}}

Thulium is quite [[electropositive]] and reacts slowly with cold water and quite quickly with hot water to form thulium hydroxide:
:{{chem2|2Tm_{(s)} + 6 H2O_{(l)} → 2Tm(OH)3_{(aq)} + 3H2_{(g)}|}}

Thulium reacts with all the [[halogen]]s. Reactions are slow at room temperature, but are vigorous above 200{{nbsp}}°C:
:{{chem2|2Tm_{(s)} + 3F2_{(g)} → 2TmF3_{(s)}|}} (white)
:{{chem2|2Tm_{(s)} + 3Cl2_{(g)} → 2TmCl3_{(s)}|}} (yellow)
:{{chem2|2Tm_{(s)} + 3Br2_{(g)} → 2TmBr3_{(s)}|}} (white)
:{{chem2|2Tm_{(s)} + 3I2_{(g)} → 2TmI3_{(s)}|}} (yellow)

Thulium dissolves readily in dilute [[sulfuric acid]] to form [[Solution (chemistry)|solution]]s containing the pale green Tm(III) ions, which exist as {{chem2|[Tm(OH2)9](3+)}} complexes:<ref>{{cite web |url= https://www.webelements.com/thulium/chemistry.html |title= Chemical reactions of Thulium |publisher=Webelements |access-date=2009-06-06}}</ref>
:{{chem2|2Tm_{(s)} + 3H2SO4_{(aq)} → 2Tm(3+)_{(aq)} + 3SO4(2-)_{(aq)} + 3H2_{(aq)}|}}

Thulium reacts with various metallic and non-metallic elements forming a range of binary compounds, including {{chem2|TmN}}, {{chem2|TmS}}, {{chem2|TmC2}}, {{chem2|Tm2C3}}, {{chem2|TmH2}}, {{chem2|TmH3}}, {{chem2|TmSi2}}, {{chem2|TmGe3}}, {{chem2|TmB4}}, {{chem2|TmB6}} and {{chem2|TmB12}}.{{citation needed|date=March 2014}} Like most lanthanides, the +3 state is most common and is the only state observed in thulium solutions.<ref name="patnaik">{{cite book |last= Patnaik |first= Pradyot |date= 2003 |title= Handbook of Inorganic Chemical Compounds |publisher= McGraw-Hill |page= 934 |isbn= 0-07-049439-8 |url= https://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA934}}</ref> Thulium exists as a {{chem2|Tm(3+)}} ion in solution. In this state, the thulium ion is surrounded by nine molecules of water.<ref name="history" /> {{chem2|Tm(3+)}} ions exhibit a bright blue luminescence.<ref name="history" /> Because it occurs late in the [[lanthanide series|series]], the +2 oxidation state can also exist, stabilized by the nearly full 4f [[electron shell]], but occurs only in solids.{{cn|date=April 2022}}

Thulium's only known oxide is [[thulium oxide|{{chem2|Tm2O3}}]]. This oxide is sometimes called "thulia".<ref name= "hist and use">{{cite book |url= https://books.google.com/books?id=yb9xTj72vNAC&pg=PA300 |title= The History and Use of Our Earth's Chemical Elements: A Reference Guide |isbn= 978-0-313-33438-2 |author= Krebs, Robert E |date= 2006|publisher= Greenwood Publishing }}</ref> Reddish-purple thulium(II) compounds can be made by the [[chemical reduction|reduction]] of thulium(III) compounds. Examples of thulium(II) compounds include the halides (except the fluoride). Some hydrated thulium compounds, such as {{chem2|TmCl3*7H2O}} and {{chem2|Tm2(C2O4)3*6H2O}} are green or greenish-white.<ref name= "concise encyclopedia">{{cite book |url=https://books.google.com/books?id=Owuv-c9L_IMC&pg=PA1105 |title=Concise Encyclopedia Chemistry |isbn=978-3-11-011451-5 |last1=Eagleson |first1=Mary |date=1994|publisher=Walter de Gruyter|page=1105}}</ref> Thulium dichloride reacts very vigorously with [[water]]. This reaction results in [[hydrogen]] gas and [[thulium(III) hydroxide|{{chem2|Tm(OH)3}}]] exhibiting a fading reddish color.{{citation needed|date=March 2014}} Combination of thulium and [[chalcogens]] results in thulium [[chalcogenide]]s.<ref>{{cite book |url=https://books.google.com/books?id=es-Pu2hI5swC |title=Advances in Inorganic Chemistry and Radiochemistry |isbn=978-0-08-057869-9 |last1=Emeléus |first1=H. J. |last2=Sharpe |first2=A. G. |date=1977|publisher=Academic Press}}</ref>

Thulium reacts with [[hydrogen chloride]] to produce hydrogen gas and thulium chloride. With [[nitric acid]] it yields thulium nitrate, or {{chem2|Tm(NO3)3}}.<ref name="cool">{{Cite web|title=Thulium|url=http://www.chemicool.com/elements/thulium.html|access-date=2023-03-10|website=www.chemicool.com}}</ref>

===Isotopes===
{{Main|Isotopes of thulium}}

The isotopes of thulium range from {{chem2|^{144}Tm}} to {{chem2|^{183}Tm}}.{{NUBASE2020|ref}}<ref name=PRL132.7>{{cite journal |first1=O. B. |last1=Tarasov |first2=A. |last2=Gade |first3=K. |last3=Fukushima |display-authors=et al. |title=Observation of New Isotopes in the Fragmentation of <sup>198</sup>Pt at FRIB |journal=Physical Review Letters |volume=132 |number=72501 |date=2024 |page=072501 |doi=10.1103/PhysRevLett.132.072501|pmid=38427880 |bibcode=2024PhRvL.132g2501T }}</ref> The primary [[decay mode]] before the most abundant stable isotope, {{chem2|^{169}Tm}}, is [[electron capture]], and the primary mode after is [[beta emission]]. The primary [[decay product]]s before {{chem2|^{169}Tm}} are element 68 ([[erbium]]) isotopes, and the primary products after are element 70 ([[ytterbium]]) isotopes.<ref name="hand">{{cite book |last= Lide |first= David R. |date= 1998|title= Handbook of Chemistry and Physics|edition= 87th |location= Boca Raton, FL |publisher= CRC Press |isbn= 0-8493-0594-2 |chapter= Section 11, Table of the Isotopes}}</ref>

Thulium-169 is thulium's only [[primordial isotope]] and is the only isotope of thulium that is thought to be stable; it is predicted to undergo [[alpha decay]] to [[holmium]]-165 with a very long half-life.<ref name="history" /><ref name="bellidecay">{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |display-authors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140–1–140–7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B |s2cid=201664098 }}</ref> The longest-lived radioisotopes are thulium-171, which has a [[half-life]] of 1.92 years, and [[thulium-170]], which has a half-life of 128.6 days. Most other isotopes have half-lives of a few minutes or less.<ref name="Nudat">{{cite web
|first=Alejandro
|last=Sonzogni
|url=https://www.nndc.bnl.gov/nudat2/reCenter.jsp?z=69&n=97
|title=Untitled
|publisher=[[National Nuclear Data Center]]
|access-date=2013-02-20
|archive-date=2020-11-21
|archive-url=https://web.archive.org/web/20201121010223/https://www.nndc.bnl.gov/nudat2/reCenter.jsp?z=69&n=97
|url-status=dead
}}</ref> 

In total, 40 isotopes and 26 [[nuclear isomer]]s of thulium have been detected.<ref name="history" /> Most isotopes of thulium lighter than 169 [[atomic mass unit]]s decay via [[electron capture]] or [[Positron emission|beta-plus decay]], although some exhibit significant [[alpha decay]] or [[proton emission]]. Heavier isotopes undergo [[beta-minus decay]].<ref name="Nudat" />