Thorium monoxide

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Thorium monoxide
IUPAC names
Thorium monoxide
Thorium(II) oxide
3D model (JSmol)
  • InChI=1S/O.Th
  • [Th]=O
Molar mass 248.04 g·mol−1
Appearance black solid[1]
face-centered cubic
a = 4.31 Å
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Thorium monoxide (thorium(II) oxide), is the binary oxide of thorium having chemical formula ThO. The covalent bond in this diatomic molecule is highly polar. The effective electric between the two atoms has been calculated to be about 80 gigavolts per centimeter, one of the largest known internal effective electric fields.[3][4][5][6]

Simple combustion of thorium in air produces thorium dioxide. However, laser ablation of thorium in the presence of oxygen gives the monoxide.[7] Additionally, exposure of a thin film of thorium to low-pressure oxygen at medium temperature forms a rapidly growing layer of thorium monoxide under a more-stable surface coating of the dioxide.[8]

At extremely high temperatures, thorium dioxide can convert to the monoxide either by a comproportionation reaction (equilibrium with liquid thorium metal) above 1,850 K (1,580 °C; 2,870 °F) or by simple dissociation (evolution of oxygen) above 2,500 K (2,230 °C; 4,040 °F).[2]


  1. ^ Stoll, Wolfgang (2011). "Thorium and Thorium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a27_001. ISBN 978-3527306732.
  2. ^ a b Hoch, Michael; Johnston, Herrick L. (1954). "The Reaction Occurring on Thoriated Cathodes". J. Am. Chem. Soc. 76 (19): 4833–4835. doi:10.1021/ja01648a018.
  3. ^ Skripnikov, L. V. (2016-12-07). "Combined 4-component and relativistic pseudopotential study of ThO for the electron electric dipole moment search". The Journal of Chemical Physics. 145 (21): 214301. arXiv:1610.00994. Bibcode:2016JChPh.145u4301S. doi:10.1063/1.4968229. ISSN 0021-9606. PMID 28799403. S2CID 42337394.
  4. ^ Denis, Malika; Fleig, Timo (2016-12-07). "In search of discrete symmetry violations beyond the standard model: Thorium monoxide reloaded". The Journal of Chemical Physics. 145 (21): 214307. Bibcode:2016JChPh.145u4307D. doi:10.1063/1.4968597. ISSN 0021-9606. PMID 28799357.
  5. ^ Skripnikov, L. V.; Petrov, A. N.; Titov, A. V. (2013-12-14). "Communication: Theoretical study of ThO for the electron electric dipole moment search". The Journal of Chemical Physics. 139 (22): 221103. arXiv:1308.0414. Bibcode:2013JChPh.139v1103S. doi:10.1063/1.4843955. ISSN 0021-9606. PMID 24329049. S2CID 42153944.
  6. ^ "The ACME EDM Experiment". Retrieved 2018-08-16.
  7. ^ Dewberry, Christopher T.; Etchison, Kerry C.; Cooke, Stephen A. (2007). "The pure rotational spectrum of the actinide-containing compound thorium monoxide". Physical Chemistry Chemical Physics. 9 (35): 4895–4897. Bibcode:2007PCCP....9.4895D. doi:10.1039/B709343H. PMID 17912418.
  8. ^ He, Heming; Majewski, Jaroslaw; Allred, David D.; Wang, Peng; Wen, Xiaodong; Rector, Kirk D. (2017). "Formation of solid thorium monoxide at near-ambient conditions as observed by neutron reflectometry and interpreted by screened hybrid functional calculations". Journal of Nuclear Materials. 487: 288–296. Bibcode:2017JNuM..487..288H. doi:10.1016/j.jnucmat.2016.12.046.