Caesium monoxide
|   Caesium cations, Cs+   Oxide anions, O2− | |
| Names | |
|---|---|
| IUPAC name Caesium oxide | |
| Other names Cesium oxide (US) | |
| Identifiers | |
| 3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.039.693 | 
| EC Number | 
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| PubChem CID | |
| 
 | |
| 
 | |
| Properties | |
| Cs2O | |
| Molar mass | 281.810 g·mol−1 | 
| Appearance | Yellow-orange solid | 
| Density | 4.65 g/cm3, solid | 
| Melting point | 490 °C (914 °F; 763 K) (under N2) | 
| Reacts to form CsOH | |
| 1534.0·10−6 cm3/mol | |
| Structure | |
| anti-CdCl2 (hexagonal) | |
| Thermochemistry | |
| Heat capacity (C) | 76.0 J/(K·mol) | 
| Std molar entropy (S⦵298) | 146.9 J/(K·mol) | 
| Std enthalpy of formation (ΔfH⦵298) | −345.8 kJ/mol | 
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
| Main hazards | Corrosive and Superbase | 
| GHS labelling: | |
| NFPA 704 (fire diamond) | |
| Flash point | non-flammable | 
| Related compounds | |
| Other anions | 
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| Other cations | |
| Related compounds | Caesium hydroxide | 
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references | |
Caesium monoxide or caesium oxide is a chemical compound with the chemical formula Cs2O. It is the simplest and most common oxide of the caesium. It forms yellow-orange hexagonal crystals.