Thorium dioxide

Thorium dioxide
Names
IUPAC names
Thorium dioxide
Thorium(IV) oxide
Other names
Thoria
Thorium anhydride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.842 Edit this at Wikidata
EC Number
  • 215-225-1
141638
UNII
UN number 2910 2909
  • Key: ZCUFMDLYAMJYST-UHFFFAOYSA-N
  • InChI=1S/2O.Th
  • O=[Th]=O
Properties
ThO2
Molar mass 264.037 g/mol[1]
Appearance white solid[1]
Odor odorless
Density 10.0 g/cm3[1]
Melting point 3,350 °C (6,060 °F; 3,620 K)[1]
Boiling point 4,400 °C (7,950 °F; 4,670 K)[1]
insoluble[1]
Solubility insoluble in alkali
slightly soluble in acid[1]
−16.0·10−6 cm3/mol[2]
2.200 (thorianite)[3]
Structure
Fluorite (cubic), cF12
Fm3m, No. 225
a = 559.74(6) pm[4]
Tetrahedral (O2−); cubic (ThIV)
Thermochemistry
65.2(2) J K−1 mol−1
−1226(4) kJ/mol
Hazards
GHS labelling:[5]
GHS06: ToxicGHS08: Health hazard
Danger
H301, H311, H331, H350, H373
P203, P260, P261, P264, P270, P271, P280, P301+P316, P302+P352, P304+P340, P316, P318, P319, P321, P330, P361+P364, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazard RA: Radioactive. E.g. plutonium
2
0
0
Special hazard RA: Radioactive. E.g. plutonium
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
400 mg/kg
Related compounds
Other anions
Thorium(IV) sulfide
Other cations
Hafnium(IV) oxide
Cerium(IV) oxide
Related compounds
Protactinium(IV) oxide
Uranium(IV) 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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Thorium dioxide (ThO2), also called thorium(IV) oxide, is a crystalline solid, often white or yellow in colour. Also known as thoria, it is mainly a by-product of lanthanide and uranium production.[4] Thorianite is the name of the mineralogical form of thorium dioxide. It is moderately rare and crystallizes in an isometric system. The melting point of thorium oxide is 3300 °C – the highest of all known oxides. Only a few elements (including tungsten and carbon) and a few compounds (including tantalum carbide) have higher melting points.[6] All thorium compounds, including the dioxide, are radioactive because there are no stable isotopes of thorium.

  1. ^ a b c d e f g Haynes, p. 4.95
  2. ^ Haynes, p. 4.136
  3. ^ Haynes, p. 4.144
  4. ^ a b Yamashita, Toshiyuki; Nitani, Noriko; Tsuji, Toshihide; Inagaki, Hironitsu (1997). "Thermal expansions of NpO2 and some other actinide dioxides". J. Nucl. Mater. 245 (1): 72–78. Bibcode:1997JNuM..245...72Y. doi:10.1016/S0022-3115(96)00750-7.
  5. ^ "Thorium dioxide". pubchem.ncbi.nlm.nih.gov.
  6. ^ Emsley, John (2001). Nature's Building Blocks (Hardcover, First ed.). Oxford University Press. pp. 441. ISBN 978-0-19-850340-8.