Caesium oxide

Caesium oxide[1][2]
IUPAC name Caesium oxide
Other names Cesium oxide (US)
Identifiers
CAS number	20281-00-9 Y
PubChem	9903865
ChemSpider	8079519 Y
EC-number	243-679-0
Jmol-3D images	Image 1
SMILES [Cs+].[Cs+].[O-2]
InChI InChI=1S/2Cs.O/q2*+1;-2 Y Key: KOPBYBDAPCDYFK-UHFFFAOYSA-N Y InChI=1/2Cs.O/q2*+1;-2 Key: KOPBYBDAPCDYFK-UHFFFAOYAW
Properties
Molecular formula	Cs2O
Molar mass	281.81 g/mol
Appearance	yellow-orange solid
Density	4.65 g/cm3, solid
Melting point	490 °C (under N2)
Solubility in water	reacts
Structure
Crystal structure	anti-CdCl2 (hexagonal)
Thermochemistry
Std enthalpy of formation ΔfHo298	-345.8 kJ/mol
Standard molar entropy So298	146.9 J K-1 mol-1
Specific heat capacity, C	76.0 J K-1 mol-1
Hazards
EU Index	not listed
Flash point	non-flammable
Related compounds
Other anions	Caesium hydroxide
Other cations	Lithium oxide Sodium oxide Potassium oxide Rubidium oxide
Y oxide (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Caesium oxide (IUPAC name) or cesium oxide describes inorganic compounds composed of caesium and oxygen. The following binary (containing only Cs and O) oxides of caesium are known: Cs₁₁O₃, Cs₄O, Cs₇O, and Cs₂O.^[3] Both the oxide and suboxides are brightly coloured. The species Cs₂O forms yellow-orange hexagonal crystals.^[1]

Uses

Caesium oxide is used in photocathodes to detect infrared signals in devices such as image intensifiers, vacuum photodiodes, photomultipliers, and TV camera tubes^[4] L. R. Koller described the first modern photoemissive surface in 1929–30 as a layer of caesium on a layer of caesium oxide on a layer of silver.^[5] It is a good electron emitter; however, its high vapor pressure limits its usefulness.^[6]

Reactions

Elemental magnesium reduces caesium oxide to elemental caesium, forming magnesium oxide as a side-product:^[7][8]

Cs₂O + Mg → Cs + MgO

Cs₂O is hygroscopic, forming the corrosive CsOH on contact with water.

References

1. ^ ^{a b} Lide, David R., ed (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. pp. 451, 514. ISBN 0-8493-0487-3. .
2. ^ Greenwood, Norman N.; Earnshaw, A. (1984). Chemistry of the Elements. Oxford: Pergamon. pp. 97–100. ISBN 0-08-022057-6. .
3. ^ Simon, A. (1997), "Group 1 and 2 Suboxides and Subnitrides — Metals with Atomic Size Holes and Tunnels", Coord. Chem. Rev. 163: 253–270, doi:10.1016/S0010-8545(97)00013-1 .
4. ^ Capper, Peter; Elliott, C. T. (2000), Infrared Detectors and Emitters, Springer, p. 14, ISBN 9780792372066, http://books.google.com/?id=HtgEcjQcgkkC&pg=PA14&dq=%22cesium+oxide%22+OR+%22caesium+oxide%22 
5. ^ Busch, Kenneth W.; Busch, Marianna A. (1990), Multielement Detection Systems for Spectrochemical Analysis, Wiley-Interscience, p. 12, ISBN 9780471819745, http://books.google.com/?id=9H0W1J-Rku4C&pg=PA12&dq=%22cesium+oxide%22+OR+%22caesium+oxide%22 
6. ^ Boolchand, Punit, ed. (2000), Insulating and Semiconducting Glasses, World Scientific, p. 855, ISBN 9789810236731, http://books.google.com/?id=QK2f4eVh7qgC&pg=PA855&dq=%22cesium+oxide%22+OR+%22caesium+oxide%22 
7. ^ Turner, Jr., Francis M., ed. (1920), The Condensed Chemical Dictionary, New York: Chemical Catalog Co., p. 121, http://books.google.com/?id=y8y0XE0nsYEC&pg=PA121&dq=%22cesium+oxide%22+OR+%22caesium+oxide%22 
8. ^ Arora, M.G. (1997), S-Block Elements, New Delhi: Anmol Publications, p. 13, ISBN 9788174885623, http://books.google.com/?id=QR3TCaKaykEC&pg=PA256&dq=%22Bromine+dioxide%22