Caesium oxide

Caesium oxide

Caesium oxide
Names
IUPAC name Caesium oxide
Other names Cesium oxide (US)
Identifiers
CAS Number	20281-00-9 Y
ChemSpider	8079519 Y
EC Number	243-679-0
Jmol 3D model	Interactive image
PubChem	9903865
InChI InChI=1S/2Cs.O/q2*+1;-2 Y Key: KOPBYBDAPCDYFK-UHFFFAOYSA-N Y InChI=1/2Cs.O/q2*+1;-2 Key: KOPBYBDAPCDYFK-UHFFFAOYAW
SMILES [Cs+].[Cs+].[O-2]
Properties
Chemical formula	Cs2O
Molar mass	281.81 g/mol
Appearance	yellow-orange solid
Density	4.65 g/cm3, solid
Melting point	490 °C (914 °F; 763 K) (under N2)
Solubility in water	reacts violently to form CsOH
Structure
Crystal structure	anti-CdCl2 (hexagonal)
Thermochemistry
Specific heat capacity (C)	76.0 J K−1 mol−1
Std molar entropy (So298)	146.9 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	-345.8 kJ/mol
Vapor pressure	{{{value}}}
Related compounds
Other anions	Caesium hydroxide
Other cations	Lithium oxide Sodium oxide Potassium oxide Rubidium oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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. Both the oxide and suboxides are brightly coloured. The species Cs₂O 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 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. It is a good electron emitter; however, its high vapor pressure limits its usefulness.

Reactions

Elemental magnesium reduces caesium oxide to elemental caesium, forming magnesium oxide as a side-product:

Cs₂O + Mg → 2Cs + MgO

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