Editing Holmium (section)

===Chemical properties===

Holmium metal tarnishes slowly in air, forming a yellowish oxide layer that has an appearance similar to that of [[iron]] rust. It burns readily to form [[holmium(III) oxide]]:<ref>{{Cite journal |last=Wahyudi |first=Tatang |date=2015 |title=Reviewing the properties of rare earth element-bearing minerals, rare-earth elements and cerium oxide compound |url=https://jurnal.tekmira.esdm.go.id/index.php/imj/article/view/293 |journal=Indonesian Mining Journal |language=en |volume=18 |issue=2 |pages=92–108 |doi=10.30556/imj.Vol18.No2.2015.293 |doi-broken-date=1 November 2024 |issn=2527-8797}}</ref>

:4 Ho + 3 O<sub>2</sub> → 2 Ho<sub>2</sub>O<sub>3</sub>

It is a relatively soft and [[Ductility|malleable]] element that is fairly [[corrosion]]-resistant and chemically stable in dry air at [[standard temperature and pressure]]. In moist air and at higher temperatures, however, it quickly [[oxidation|oxidizes]], forming a yellowish oxide.<ref>{{Cite journal |last=Phillips |first=W. L. |date=1964-08-01 |title=Oxidation of several lanthanide elements |url=https://dx.doi.org/10.1016/0022-5088%2864%2990056-6 |journal=Journal of the Less Common Metals |language=en |volume=7 |issue=2 |pages=139–143 |doi=10.1016/0022-5088(64)90056-6 |issn=0022-5088 |url-access=subscription}}</ref> In pure form, holmium possesses a metallic, bright silvery luster.

Holmium is quite electropositive: on the Pauling [[electronegativity]] scale, it has an electronegativity of 1.23.<ref name="Win">{{cite web |last1=Winter |first1=Mark J. |title=Holmium - 67Ho: electronegativity |url=https://winter.group.shef.ac.uk/webelements/holmium/electronegativity.html#:~:text=Holmium%20%2D%2067Ho%3A%20electronegativity&text=The%20first%20scale%20of%20electronegativity,)%20to%203.98%20(fluorine). |website=WebElements |publisher=[[University of Sheffield]] |access-date=4 August 2023}}</ref> It is generally trivalent. It reacts slowly with cold water and quickly with hot water to form holmium(III) hydroxide:<ref>{{Cite journal |last1=An |first1=Tao |last2=Dou |first2=Chunyue |last3=Ju |first3=Jinning |last4=Wei |first4=Wenlong |last5=Ji |first5=Quanzeng |date=2019-06-01 |title=Microstructure, morphology, wettability and mechanical properties of Ho<sub>2</sub>O<sub>3</sub> films prepared by glancing angle deposition |url=https://www.sciencedirect.com/science/article/pii/S0042207X19302428 |journal=Vacuum |language=en |volume=164 |pages=405–410 |doi=10.1016/j.vacuum.2019.03.057 |bibcode=2019Vacuu.164..405A |s2cid=133466738 |issn=0042-207X |url-access=subscription}}</ref>
:2 Ho (s) + 6 H<sub>2</sub>O (l) → 2 Ho(OH)<sub>3</sub> (aq) + 3 H<sub>2</sub> (g)

Holmium metal reacts with all the stable [[halogen]]s:<ref name="Webelements" />
:2 Ho (s) + 3 F<sub>2</sub> (g) → 2 [[Holmium(III) fluoride|HoF<sub>3</sub>]] (s) [pink]

:2 Ho (s) + 3 Cl<sub>2</sub> (g) → 2 [[Holmium(III) chloride|HoCl<sub>3</sub>]] (s) [yellow]

:2 Ho (s) + 3 Br<sub>2</sub> (g) → 2 [[Holmium(III) bromide|HoBr<sub>3</sub>]] (s) [yellow]

:2 Ho (s) + 3 I<sub>2</sub> (g) → 2 [[Holmium(III) iodide|HoI<sub>3</sub>]] (s) [yellow]

Holmium dissolves readily in dilute [[sulfuric acid]] to form [[Solution (chemistry)|solution]]s containing the yellow Ho(III) ions, which exist as a [Ho(OH<sub>2</sub>)<sub>9</sub>]<sup>3+</sup> complexes:<ref name="Webelements">{{cite web| url =https://www.webelements.com/holmium/chemistry.html| title =Chemical reactions of Holmium| publisher=Webelements| access-date=2009-06-06}}</ref>

:2 Ho (s) + 3 H<sub>2</sub>SO<sub>4</sub> (aq) → 2 Ho<sup>3+</sup> (aq) + 3 {{chem|SO|4|2-}} (aq) + 3 H<sub>2</sub> (g)

====Oxidation states====
As with many lanthanides, holmium is usually found in the +3 [[oxidation state]], forming compounds such as [[holmium(III) fluoride]] (HoF<sub>3</sub>) and [[holmium(III) chloride]] (HoCl<sub>3</sub>).  Holmium in solution is in the form of Ho<sup>3+</sup> surrounded by nine molecules of water. Holmium dissolves in [[acid]]s.<ref name="emsley226">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks|page=226|date=2011}}</ref> However, holmium is also found to exist in +2, +1 and 0 oxidation states.<ref>{{Cite web |title=Periodic Table of Elements: Los Alamos National Laboratory |url=https://periodic.lanl.gov/67.shtml |access-date=2024-06-02 |website=periodic.lanl.gov}}</ref><ref name=":0" />