Editing Thulium (section)

===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>