Actinium(III) oxide

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Actinium(III) oxide
Actinium sesquioxide.jpg
Unit cell, ball and stick model of actinium(III) oxide
IUPAC name
Actinium(III) oxide
Systematic IUPAC name
Actinium(3+) oxide
Other names
Actinium sesquioxide
3D model (Jmol)
ECHA InfoCard 100.031.275
Molar mass 502.00 g·mol−1
Appearance white
Trigonal, hP5
P-3m1, No. 164
Related compounds
Other cations
Scandium(III) oxide
Yttrium(III) oxide
Lanthanum(III) 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

Actinium(III) oxide is a chemical compound containing the rare radioactive element actinium. It has the formula Ac2O3. It is similar to its corresponding lanthanum compound, lanthanum(III) oxide, and contains actinium in the oxidation state +3.[1][2] Actinium oxide is not to be confused with Ac2O (acetic anhydride), where Ac is an abbreviation for acetyl instead of the symbol of the element actinium.


  • Ac2O3 + 6HF → 2AcF3 + 3H2O
  • Ac2O3 + 6HCl → 2AcCl3 + 3H2O
  • 4Ac(NO3)3 → 2Ac2O3 + 12NO2 + 3O2
  • 4Ac + 3O2 → 2Ac2O3
  • Ac2O3 + 2AlBr3 → 2AcBr3 + Al2O3
  • 2Ac(OH)3 → Ac2O3 + 3H2O
  • Ac2(C2O4)3 → Ac2O3 + 3CO2 + 3CO
  • Ac2O3 + H2S → Ac2S3 + 3H2O


  1. ^ Actinium, Great Soviet Encyclopedia (in Russian)
  2. ^ Sherman, Fried; Hagemann, French; Zachariasen, W. H. (1950). "The Preparation and Identification of Some Pure Actinium Compounds". Journal of the American Chemical Society. 72 (2): 771–775. doi:10.1021/ja01158a034.