Editing Samarium (section)

== Chemical properties ==

In air, samarium slowly oxidizes at room temperature and spontaneously ignites at {{convert|150|C|F}}.<ref name="emsley" /><ref name="CRC" /> Even when stored under [[mineral oil]], samarium gradually oxidizes and develops a grayish-yellow powder of the [[oxide]]-[[hydroxide]] mixture at the surface. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as [[argon]].

Samarium is quite electropositive and reacts slowly with cold water and rapidly with hot water to form samarium hydroxide:<ref name="we" />
: {{chem2|2Sm_{(s)} + 6H2O_{(l)} → 2Sm(OH)3_{(aq)} + 3H2_{(g)}|}}

Samarium dissolves readily in dilute [[sulfuric acid]] to form solutions containing the yellow<ref name="g1243">[[#Greenwood|Greenwood]], p. 1243</ref> to pale green Sm(III) ions, which exist as {{chem2|[Sm(OH2)9](3+)|}} complexes:<ref name="we">{{cite web| url =https://www.webelements.com/samarium/chemistry.html| title =Chemical reactions of Samarium| publisher=Webelements| access-date=2009-06-06}}</ref>

: {{chem2|2Sm_{(s)} + 3H2SO4_{(aq)} → 2Sm(3+)_{(aq)} + 3SO4(2-)_{(aq)} + 3H2_{(g)}|}}

Samarium is one of the few lanthanides with a relatively accessible +2 oxidation state, alongside Eu and Yb.<ref>{{Cite book |title=The lanthanides and actinides: synthesis, reactivity, properties and applications |date=2022 |editor=Stephen T. Liddle |editor2=David P. Mills |editor3=Louise S. Natrajan |isbn=978-1-80061-015-6 |location=London |oclc=1251740566 |page=213}}</ref> {{chem2|Sm(2+)}} ions are blood-red in aqueous solution.<ref name="g1248">[[#Greenwood|Greenwood]], p. 1248</ref>