caesium monoxide
{{Chembox
| Watchedfields = changed
| verifiedrevid = 443164898
| Reference = {{RubberBible87th|pages=451, 514}}.{{Greenwood&Earnshaw1st|pages=97–100}}.
| Name = Caesium oxide
| ImageFile = Caesium-oxide-xtal-3D-SF.png
| ImageCaption = {{legend|rgb(96,0,128)|Caesium cations, {{chem2|Cs+}}}}{{legend|red|Oxide anions, {{chem2|O(2−)}}}}
| ImageName = Caesium oxide
| IUPACName = Caesium oxide
| OtherNames = Cesium oxide (US)
|Section1={{Chembox Identifiers
| InChI = 1/2Cs.O/q2*+1;-2
| SMILES = [Cs+].[Cs+].[O-2]
| InChIKey = KOPBYBDAPCDYFK-UHFFFAOYAW
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2Cs.O/q2*+1;-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = KOPBYBDAPCDYFK-UHFFFAOYSA-N
| CASNo = 20281-00-9
| CASNo_Ref = {{cascite|correct|CAS}}
| EC_number = 243-679-0
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 8079519
| RTECS =
| PubChem = 9903865
}}
|Section2={{Chembox Properties
| Cs=2|O=1
| Appearance = Yellow-orange solid
| Density = 4.65 g/cm3, solid
| Solubility = Reacts to form CsOH
| MeltingPtC = 490
| MeltingPt_notes = (under Nitrogen)
| BoilingPt =
| MagSus = 1534.0·10−6 cm3/mol
}}
|Section3={{Chembox Structure
| Coordination =
| CrystalStruct = Cadmium chloride (hexagonal)
}}
|Section4={{Chembox Thermochemistry
| DeltaHf = −345.8 kJ/mol
| Entropy = 146.9 J/(K·mol)
| HeatCapacity = 76.0 J/(K·mol)
}}
|Section7={{Chembox Hazards
| MainHazards = Corrosive and Superbase
| GHSPictograms = {{GHS05}}{{GHS08}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = W
| FlashPt = non-flammable
}}
|Section8={{Chembox Related
| OtherAnions = {{ubl|Caesium sulfide|Caesium selenide|Caesium telluride|Caesium polonide}}
| OtherCations = {{ubl|Lithium oxide|Sodium oxide|Potassium oxide|Rubidium oxide}}
| OtherFunction = {{ubl|Caesium suboxide|Caesium peroxide|Caesium sesquioxide|Caesium superoxide|Caesium ozonide}}
| OtherFunction_label = caesium oxides
| OtherCompounds = Caesium hydroxide
}}
}}
Caesium monoxide or caesium oxide is a chemical compound with the chemical formula {{chem2|Cs2O|auto=1}}. It is the simplest and most common oxide of the caesium. It forms yellow-orange hexagonal crystals.
Uses
Caesium oxide is used in photocathodes to detect infrared signals in devices such as image intensifiers, vacuum photodiodes, photomultipliers, and TV camera tubes{{Citation | last1 = Capper | first1 = Peter | last2 = Elliott | first2 = C. T. | year = 2000 | title = Infrared Detectors and Emitters | publisher = Springer | isbn = 978-0-7923-7206-6 | page = 14 | url = https://books.google.com/books?id=HtgEcjQcgkkC&q=%22cesium+oxide%22+OR+%22caesium+oxide%22&pg=PA14}}
L. R. Koller described the first modern photoemissive surface in 1929–1930 as a layer of caesium on a layer of caesium oxide on a layer of silver.{{Citation | last1 = Busch | first1 = Kenneth W. | last2 = Busch | first2 =Marianna A. | year = 1990 | title = Multielement Detection Systems for Spectrochemical Analysis | publisher = Wiley-Interscience | isbn = 978-0-471-81974-5 | page = 12 | url = https://books.google.com/books?id=9H0W1J-Rku4C&q=%22cesium+oxide%22+OR+%22caesium+oxide%22&pg=PA12}} It is a good electron emitter; however, its high vapor pressure limits its usefulness.{{Citation | editor-first = Punit | editor-last = Boolchand | year = 2000 | title = Insulating and Semiconducting Glasses | publisher = World Scientific | isbn = 978-981-02-3673-1 | page = 855 | bibcode = 2000isg..book.....B | url = https://books.google.com/books?id=QK2f4eVh7qgC&q=%22cesium+oxide%22+OR+%22caesium+oxide%22&pg=PA855}}
Reactions
Elemental magnesium reduces caesium oxide to elemental caesium, forming magnesium oxide as a side-product:
{{Citation | editor-last= Turner Jr. | editor-first= Francis M. | year = 1920 | title = The Condensed Chemical Dictionary | publication-place = New York | publisher = Chemical Catalog Co. | page = 121 | url = https://books.google.com/books?id=y8y0XE0nsYEC&q=%22cesium+oxide%22+OR+%22caesium+oxide%22&pg=PA121}}
{{Citation | last = Arora | first = M.G. | year = 1997 | title = S-Block Elements | publication-place = New Delhi | publisher = Anmol Publications | isbn = 978-81-7488-562-3 | page = 13 | url = https://books.google.com/books?id=QR3TCaKaykEC&q=%22Bromine+dioxide%22&pg=PA256}}
:{{chem2|Cs2O + Mg → 2 Cs + MgO}}
{{chem2|Cs2O}} is hygroscopic, forming the corrosive CsOH on contact with water.