Thorium dioxide

Thorium dioxide
Names
	IUPAC names Thorium dioxide; Thorium(IV) oxide
	Other names Thoria; Thorium anhydride
Identifiers
CAS Number	1314-20-1 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:37339;
ChemSpider	14124;
ECHA InfoCard	100.013.842
EC Number	215-225-1;
Gmelin Reference	141638
PubChem CID	14808;
UNII	9XA7X17UQC ;
UN number	2910 2909
CompTox Dashboard (EPA)	DTXSID0051657 ;
	InChI Key: ZCUFMDLYAMJYST-UHFFFAOYSA-N; InChI=1S/2O.Th;
	SMILES O=[Th]=O;
Properties
Chemical formula	ThO2
Molar mass	264.037 g/mol
Appearance	white solid
Odor	odorless
Density	10.0 g/cm3
Melting point	3,350 °C (6,060 °F; 3,620 K)
Boiling point	4,400 °C (7,950 °F; 4,670 K)
Solubility in water	insoluble
Solubility	insoluble in alkali; slightly soluble in acid
Magnetic susceptibility (χ)	−16.0·10−6 cm3/mol
Refractive index (nD)	2.200 (thorianite)
Structure
Crystal structure	Fluorite (cubic), cF12
Space group	Fm3m, No. 225
Lattice constant	a = 559.74(6) pm
Coordination geometry	Tetrahedral (O2−); cubic (ThIV)
Thermochemistry
Std molar; entropy (S⦵298)	65.2(2) J K−1 mol−1
Std enthalpy of; formation (ΔfH⦵298)	−1226(4) kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H311, H331, H350, H373
Precautionary statements	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)	2 0 0
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	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). verify (what is ?) Infobox references

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.

^ ^a ^b ^c ^d ^e ^f ^g Haynes, p. 4.95
^ Haynes, p. 4.136
^ Haynes, p. 4.144
^ ^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.
^ "Thorium dioxide". pubchem.ncbi.nlm.nih.gov.
^ Emsley, John (2001). Nature's Building Blocks (Hardcover, First ed.). Oxford University Press. pp. 441. ISBN 978-0-19-850340-8.

[crc1-1] ^ ^a ^b ^c ^d ^e ^f ^g Haynes, p. 4.95

[2] Haynes, p. 4.136

[3] Haynes, p. 4.144

[Yamashita-4] 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.

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Names

IUPAC names Thorium dioxide Thorium(IV) oxide
Other names Thoria Thorium anhydride
Identifiers
CAS Number	1314-20-1^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37339
ChemSpider	14124
ECHA InfoCard	100.013.842
EC Number	215-225-1
Gmelin Reference	141638
PubChem CID	14808
UNII	9XA7X17UQC^Y
UN number	2910 2909
CompTox Dashboard (EPA)	DTXSID0051657
InChI Key: ZCUFMDLYAMJYST-UHFFFAOYSA-N InChI=1S/2O.Th
SMILES O=[Th]=O
Properties
Chemical formula	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]
Solubility in water	insoluble^[1]
Solubility	insoluble in alkali slightly soluble in acid^[1]
Magnetic susceptibility (χ)	−16.0·10⁻⁶ cm³/mol^[2]
Refractive index (n_D)	2.200 (thorianite)^[3]
Structure
Crystal structure	Fluorite (cubic), cF12
Space group	Fm3m, No. 225
Lattice constant	a = 559.74(6) pm^[4]
Coordination geometry	Tetrahedral (O²⁻); cubic (Th^IV)
Thermochemistry
Std molar entropy (S^⦵₂₉₈)	65.2(2) J K⁻¹ mol⁻¹
Std enthalpy of formation (Δ_fH^⦵₂₉₈)	−1226(4) kJ/mol
Hazards
GHS labelling:^[5]
Pictograms
Signal word	Danger
Hazard statements	H301, H311, H331, H350, H373
Precautionary statements	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)	2 0 0
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD₅₀ (median dose)	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). N verify (what is ^YN ?) Infobox references