Editing Caesium (section)

===Chemical properties===
[[File:Cesium water.theora.ogv|left|thumb|Addition of a small amount of caesium to cold water is explosive.|alt=A person adds a small amount of metal to a petri dish with cold water which produces a small explosion.]]
Caesium metal is highly reactive and [[pyrophoricity|pyrophoric]]. It ignites spontaneously in air, and reacts explosively with water even at low temperatures, more so than the other [[alkali metal]]s.<!--YES INCLUDING FRANCIUM--><ref name="USGS"/> It reacts with ice at temperatures as low as {{convert|−116|C}}.<ref name="KanerACS"/> Because of this high reactivity, caesium metal is classified as a [[hazardous material]]. It is stored and shipped in dry, saturated hydrocarbons such as [[mineral oil]]. It can be handled only under [[inert gas]], such as [[argon]]. However, a caesium-water explosion is often less powerful than a [[sodium]]-water explosion with a similar amount of sodium. This is because caesium explodes instantly upon contact with water, leaving little time for [[hydrogen]] to accumulate.<ref>Gray, Theodore (2012) ''The Elements'', Black Dog & Leventhal Publishers, p. 131, {{ISBN|1-57912-895-5}}.</ref> Caesium can be stored in vacuum-sealed [[borosilicate glass]] [[ampoule]]s. In quantities of more than about {{convert|100|g|oz}}, caesium is shipped in hermetically sealed, stainless steel containers.<ref name="USGS"/>

The chemistry of caesium is similar to that of other alkali metals, in particular [[rubidium]], the element above caesium in the periodic table.<ref name="greenwood"/> As expected for an alkali metal, the only common oxidation state is +1. It differs from this value in caesides, which contain the Cs<sup>−</sup> anion and thus have caesium in the −1 oxidation state.<ref name="caeside2"/> Under conditions of extreme pressure (greater than 30&nbsp;[[pascal (unit)|GPa]]), theoretical studies indicate that the inner 5p electrons could form chemical bonds, where caesium would behave as the seventh 5p element, suggesting that higher caesium fluorides with caesium in oxidation states from +2 to +6 could exist under such conditions.<ref>{{Cite journal |last1=Miao |first1=Maosheng |last2=Sun |first2=Yuanhui |last3=Zurek |first3=Eva |last4=Lin |first4=Haiqing |date=2020 |title=Chemistry under high pressure |url=https://www.nature.com/articles/s41570-020-0213-0 |journal=Nature Reviews Chemistry |language=en |volume=4 |issue=10 |pages=508–527 |doi=10.1038/s41570-020-0213-0 |issn=2397-3358}}</ref><ref>{{cite web |last=Moskowitz |first=Clara |title=A Basic Rule of Chemistry Can Be Broken, Calculations Show |url=http://www.scientificamerican.com/article.cfm?id=chemical-bonds-inner-shell-electrons |work=Scientific American |access-date=22 November 2013 |archive-date=22 November 2013 |archive-url=https://web.archive.org/web/20131122052856/http://www.scientificamerican.com/article.cfm?id=chemical-bonds-inner-shell-electrons |url-status=live }}</ref> Some slight differences arise from the fact that it has a higher [[atomic mass]] and is more [[electronegativity|electropositive]] than other (nonradioactive) alkali metals.<ref name="HollemanAF">{{cite book |publisher=Walter de Gruyter |date=1985 |edition=91–100 |pages=953–955 |isbn=978-3-11-007511-3 |title=Lehrbuch der Anorganischen Chemie |first1=Arnold F. |last1=Holleman |last2=Wiberg |first2=Egon |last3=Wiberg |first3=Nils |chapter=Vergleichende Übersicht über die Gruppe der Alkalimetalle |language=de}}</ref> Caesium is the most electropositive chemical element.<ref name="KanerACS"/> The caesium ion is also larger and [[HSAB theory|less "hard"]] than those of the lighter [[alkali metals]].